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3,700 | Amiodarone for ACLS: a critical evaluation. | Years ago, William Osler taught physicians, "Be not the first nor the last to adopt a therapy." This continues to be sage advice. Clinicians should be cautious in considering the use of amiodarone in a field setting for cardiac arrest until studies clearly show a benefit over drugs currently in use. The endpoint of the only cardiac arrest study available shows improved survival when amiodarone is combined with other drugs over placebo until the patient gets to the emergency department, but is not a comparison with other current drugs nor had any effect on long-term survival or functioning neurologic status. As previously cited, amiodarone was comparable with bretylium in treating recurrent VT/VF in one controlled study. Further study of this and other ACLS drugs is imperative. In summary, amiodarone should be reclassified as either a class indeterminate agent when used alone ("no harm but no benefit ... evidence insufficient to support final class decision") or a class IIb agent ("acceptable and useful ... supported by fair to good evidence") when used in addition to other therapies in the treatment of ventricular fibrillation and pulseless ventricular tachycardia. There is not sufficient evidence to move amiodarone to first-line therapy in the "out-of-hospital" cardiac arrest. This evidence may be available in the future and would then change this recommendation. |
3,701 | Arrhythmias after pediatric lung transplantation. | Atrial arrhythmias have been reported after congenital heart surgery involving extensive atrial suture lines. Experimental studies involving bilateral lung transplantation (Tx) suggest that the left atrial suture lines predispose to atrial flutter. The overall incidence and type of arrhythmias after pediatric lung Tx have not previously been described and therefore the purpose of this study was to prospectively screen and describe arrhythmias in a subset of our lung transplant population. Over a 1-yr study period, all recipients of bilateral lung Tx were admitted to a full-disclosure telemetry unit. Single-lead electrocardiograms were recorded continuously and reviewed daily via a beat-by-beat analysis. A total of 314 patient days (range 9-93, median 43 days) were recorded from seven patients. The incidence of arrhythmias observed per total patient days included junctional escape rhythm (4.8%), non-sustained ventricular tachycardia (4.1%), accelerated junctional (2.5%), sinus bradycardia (2.2%), non-sustained supraventricular tachycardia (1.3%), ectopic atrial tachycardia (1.0%), sustained ventricular tachycardia (0.3%), junctional ectopic tachycardia (0.3%), and second degree heart block (0.3%). No patient had sustained supraventricular tachycardia, atrial flutter, atrial fibrillation, or complete heart block. Arrhythmias were treated in two patients. During the follow-up period, one patient received amiodarone for ventricular tachycardia (which was also noted and treated prior to transplant). We conclude that among pediatric lung transplant recipients admitted for their transplant surgery, arrhythmia is uncommon and rarely requires therapy. |
3,702 | Ischemic and anesthetic preconditioning reduces cytosolic [Ca2+] and improves Ca(2+) responses in intact hearts. | Ca(+) loading during reperfusion after myocardial ischemia is linked to reduced cardiac function. Like ischemic preconditioning (IPC), a volatile anesthetic given briefly before ischemia can reduce reperfusion injury. We determined whether IPC and sevoflurane preconditioning (SPC) before ischemia equivalently improve mechanical and metabolic function, reduce cytosolic Ca(2+) loading, and improve myocardial Ca(2+) responsiveness. Four groups of guinea pig isolated hearts were perfused: no ischemia, no treatment before 30-min global ischemia and 60-min reperfusion (control), IPC (two 2-min occlusions) before ischemia, and SPC (3.5 vol%, two 2-min exposures) before ischemia. Intracellular Ca(2+) concentration ([Ca(2+)](i)) was measured at the left ventricular (LV) free wall with the fluorescent probe indo 1. Ca(2+) responsiveness was assessed by changing extracellular [Ca(2+)]. In control hearts, initial reperfusion increased diastolic [Ca(2+)] and diastolic LV pressure (LVP), and the maximal and minimal derivatives of LVP (dLVP/dt(max) and dLVP/dt(min), respectively), O(2) consumption, and cardiac efficiency (CE). Throughout reperfusion, IPC and SPC similarly reduced ischemic contracture, ventricular fibrillation, and enzyme release, attenuated rises in systolic and diastolic [Ca(2+)], improved contractile and relaxation indexes, O(2) consumption, and CE, and reduced infarct size. Diastolic [Ca(2+)] at 50% dLVP/dt(min) was right shifted by 32-53 +/- 8 nM after 30-min reperfusion for all groups. Phasic [Ca(2+)] at 50% dLVP/dt(max) was not altered in control but was left shifted by -235 +/- 40 nM [Ca(2+)] after IPC and by -135 +/- 20 nM [Ca(2+)] after SPC. Both SPC and IPC similarly reduce Ca(2+) loading, while augmenting contractile responsiveness to Ca(2+), improving postischemia cardiac function and attenuating permanent damage. |
3,703 | Selective AV nodal vagal stimulation improves hemodynamics during acute atrial fibrillation in dogs. | Although the atrioventricular node (AVN) plays a vital role in blocking many of the atrial impulses from reaching the ventricles during atrial fibrillation (AF), a rapid irregular ventricular rate nevertheless persists. The goals of the present study were to explore the feasibility of novel epicardial selective vagal nerve stimulation for slowing of the ventricular rate during AF and to characterize the hemodynamic benefits in vivo. Electrophysiological-echocardiographic experiments were performed on 11 anesthetized open-chest dogs. Hemodynamic measurements were performed during three distinct periods: 1) sinus rate, 2) AF, and 3) AF with vagal nerve stimulation. AF was associated with significant deterioration of all measured parameters (P < 0.025). The vagal nerve stimulation produced slowing of the ventricular rate, significant reversal of the pressure and contractile indexes (P < 0.025), and a sharp reduction in one-half of the abortive ventricular contractions. The present study provides comprehensive evidence that slowing of the ventricular rate during AF by selective ganglionic stimulation of the vagal nerves that innervate the AVN successfully improved the hemodynamic responses. |
3,704 | Structural remodelling during chronic atrial fibrillation: act of programmed cell survival. | Atrial fibrillation is the most common cardiac arrhythmia with an overall prevalence of almost 1%. Increasing prevalence and associated risks such as stroke and mortality have increased the need for better and more reliable therapeutic treatment. This has stimulated research to elucidate the pathophysiological mechanisms underlying atrial fibrillation. Atrial fibrillation is primarily characterised by electrical remodelling and functional deterioration. Both phenomena are reversible but after prolonged duration of atrial fibrillation, a discrepancy occurs between rapid electrical remodelling and slow recovery of contractile function. Recent studies have indicated that morphological remodelling might underlie this incongruity. In experimental models of lone atrial fibrillation, the remodelling involves cellular changes that are reminiscent of dedifferentiation and are characterised by cellular volume increase, myolysis, glycogen accumulation, mitochondrial changes and chromatin redistribution. The absence of clear signs of degeneration in these models points towards cardiomyocyte adaptation or a mechanism of programmed cell survival. In patients with atrial fibrillation cardiomyocyte degeneration does occur along with dedifferentiation which might be the result of underlying cardiac pathologies or longer duration of atrial fibrillation. In this review we focus on structural remodelling during atrial fibrillation. The different aspects of histological and ultrastructural changes as well as their role in atrial dysfunction and cardiomyocyte survival are discussed. We briefly describe the underlying molecular remodelling. and possible mechanisms responsible for remodelling involving calcium overload and stretch are presented. |
3,705 | Adverse cardiac events after surgery: assessing risk in a veteran population. | To establish rates of and risk factors for cardiac complications after noncardiac surgery in veterans.</AbstractText>Prospective cohort study.</AbstractText>A large urban veterans affairs hospital.</AbstractText>One thousand patients with known or suspected cardiac problems undergoing 1,121 noncardiac procedures.</AbstractText>Patients were assessed preoperatively for important clinical variables. Postoperative evaluation was done by an assessor blinded to preoperative status with a daily physical examination, electrocardiogram, and creatine kinase with MB fraction until postoperative day 6, day of discharge, death, or reoperation (whichever occurred earliest). Serial electrocardiograms, enzymes, and chest radiographs were obtained as indicated. Severe cardiac complications included cardiac death, cardiac arrest, myocardial infarction, ventricular tachycardia, and fibrillation and pulmonary edema. Serious cardiac complications included the above, heart failure, and unstable angina.</AbstractText>Severe and serious complications were seen in 24% and 32% of aortic, 8.3% and 10% of carotid, 11.8% and 14.7% of peripheral vascular, 9.0% and 13.1% of intraabdominal/intrathoracic, 2.9% and 3.3% of intermediate-risk (head and neck and major orthopedic procedures), and 0.27% and 1.1% of low-risk procedures respectively. The five associated patient-specific risk factors identified by logistic regression are: myocardial infarction < 6 months (odds ratio [OR], 4.5; 95% confidence interval [CI], 1.9 to 12.9), emergency surgery (OR, 2.6; 95% CI, 1.2 to 5.6), myocardial infarction > 6 months (OR, 2.2; 95% CI, 1.4 to 3.5), heart failure ever (OR, 1.9; 95% CI, 1.2 to 3.0), and rhythm other than sinus (OR, 1.7; 95% CI, 0.9 to 3.2). Inclusion of the planned operative procedure significantly improves the predictive ability of our risk model.</AbstractText>Five patient-specific risk factors are associated with high risk for cardiac complications in the perioperative period of noncardiac surgery in veterans. Inclusion of the operative procedure significantly improves the predictive ability of the risk model. Overall cardiac complication rates (pretest probabilities) are established for these patients. A simple nomogram is presented for calculation of post-test probabilities by incorporating the operative procedure.</AbstractText> |
3,706 | Alcohol and the heart. | ALCOHOLISM IN GENERAL: Alcoholism is one of the major health problems in the world. Alcohol consumption has an impact on different body systems like the central nervous system, the gastrointestinal tract, the hematopoetic organs, and the cardiovascular system. Alcohol interferes with other medications, and drinking can exacerbate a variety of medical illnesses.</AbstractText>In the heart, alcohol and its metabolite acetaldehyde confer a toxic effect on mitochondria as well as on the sarcoplasmatic reticulum, which is dependent on both the mean daily consumption and the duration of alcohol intake. A wide range of toxic effects of alcohol in distinct individuals can be observed and modest doses of alcohol can exert beneficial effects on the cardiovascular system probably by an increase in high density lipoprotein cholesterol (HDL) or changes in blood clotting mechanisms. Detrimental effects of alcohol on the heart comprise a decrease in myocardial contractility, hypertension, atrial and ventricular arrhythmias, and secondary non-ischemic dilated cardiomyopathy. After consuming large quantities of alcohol over years, alcoholic cardiomyopathy may develop, which presents with dilation and impaired contractility of the left or both ventricles. Endomyocardial biopsies of patients with alcoholic cardiomyopathy reveal in up to 30% of all cases myocarditis with lymphocytic infiltrates.</AbstractText>Abstinence after development of milder heart failure can stop progression or even reverse symptoms in some cases, otherwise severe heart failure ensues leading to a poor prognosis. Except abstinence, treatment of alcoholic cardiomyopathy is based on the regimen of therapy for heart failure to reduce the size of the dilated heart and to mitigate the symptoms of heart failure.</AbstractText> |
3,707 | Commodio cordis: an underappreciated cause of sudden cardiac death in young patients: assessment and management in the ED. | Commotio cordis is the condition of sudden cardiac death or near sudden cardiac death after blunt, low-impact chest wall trauma in the absence of structural cardiac abnormality. Ventricular fibrillation is the most commonly reported induced arrhythmia in commotio cordis. Blunt impact injury to the chest with a baseball is the most common mechanism. Survival rates for commotio cordis are low, even with prompt CPR and defibrillation. |
3,708 | A comparison of biphasic and monophasic waveform defibrillation after prolonged ventricular fibrillation. | To compare the effects of biphasic defibrillation waveforms and conventional monophasic defibrillation waveforms on the success of initial defibrillation, postresuscitation myocardial function, and duration of survival after prolonged duration of untreated ventricular fibrillation (VF), including the effects of epinephrine.</AbstractText>Prospective, randomized, animal study.</AbstractText>Animal laboratory and university-affiliated research and educational institute.</AbstractText>Domestic pigs.</AbstractText>VF was induced in 20 anesthetized domestic pigs receiving mechanical ventilation. After 10 min of untreated VF, the animals were randomized. Defibrillation was attempted with up to three 150-J biphasic waveform shocks or a conventional sequence of 200-J, 300-J, and 360-J monophasic waveform shocks. When reversal of VF was unsuccessful, precordial compression was performed for 1 min, with or without administration of epinephrine. The protocol was repeated until spontaneous circulation was restored or for a maximum of 15 min.</AbstractText>No significant differences in the success of initial resuscitation or in the duration of survival were observed. However, significantly less impairment of myocardial function followed biphasic shocks. Administration of epinephrine reduced the total electrical energy required for successful resuscitation with both biphasic and monophasic waveform shocks.</AbstractText>Lower-energy biphasic waveform shocks were as effective as conventional higher-energy monophasic waveform shocks for restoration of spontaneous circulation after 10 min of untreated VF. Significantly better postresuscitation myocardial function was observed after biphasic waveform defibrillation. Administration of epinephrine after prolonged cardiac arrest decreased the total energy required for successful resuscitation.</AbstractText> |
3,709 | Survival from out-of-hospital cardiac arrest in the Geelong region of Victoria, Australia. | To study the outcome from prehospital cardiac arrest managed by ambulance personnel, and to examine overall survival rates from successful resuscitation.</AbstractText>A retrospective analysis was made of 115 patient care records of prehospital cardiac arrests with attempted resuscitation between July 1996 and September 1999. All cases had a presumed primary cardiac cause for their cardiac arrest.</AbstractText>Overall survival, defined as admitted to hospital alive, was 22 subjects (19.1%), with five subjects (4.3%) being discharged from hospital neurologically intact. Of the patients who survived to the emergency department, six (5%) had initially presented in pulseless electrical activity and 16 (14%) presented with ventricular fibrillation. No patients presented with ventricular tachycardia and no survivors presented in asystole. Median response interval from time of call to arrival of initial crew at patient's side was 9 min. No patients survived when response interval was greater than 14 min. Bystander cardiopulmonary resuscitation was being performed on 55 patients (48%) on arrival of initial ambulance crew; 68.2% of patients surviving to hospital having had bystander cardiopulmonary resuscitation.</AbstractText>Decreasing time delays in accessing the patient is crucial to improving outcome in out-of-hospital cardiac arrest.</AbstractText> |
3,710 | Mechanism of ventricular defibrillation for near-defibrillation threshold shocks: a whole-heart optical mapping study in swine. | To study the mechanism by which shocks succeed (SDF) or fail (FDF) to defibrillate, global cardiac activation and recovery and their relationship to defibrillation outcome were investigated for shock strengths with approximately equal SDF and FDF outcomes (DFT(50)).</AbstractText>In 6 isolated pig hearts, dual-camera video imaging was used to record optically from approximately 8000 sites on the anterior and posterior ventricular surfaces before and after 10 DFT(50) biphasic shocks. The interval between the shock and the last ventricular fibrillation activation preceding the shock (coupling interval, CI) and the time from shock onset to 90% repolarization of the immediate postshock action potential (RT(90)) were determined at all sites. Of 60 shocks, 31 were SDF. The CI (59+/-7 versus 52+/-6 ms) and RT(90) (108+/-19 versus 88+/-8 ms) were significantly longer for SDF than FDF episodes. Spatial dispersions of CI (36+/-5 versus 34+/-3 ms) and RT(90) (40+/-16 versus 40+/-8 ms) were not significantly different for SDF versus FDF episodes. The first global activation cycle appeared focally on the left ventricular apical epicardium 78+/-32 ms after the shock.</AbstractText>For near-threshold shocks, defibrillation outcome correlates with the electrical state of the heart at the time of the shock and on RT. Global dispersion of RT was similar in both SDF and FDF episodes, suggesting that it is not crucial in determining defibrillation outcome after DFT(50) shocks.</AbstractText> |
3,711 | The role of prostaglandins in the antiarrhythmic effect of ischemic preconditioning. | The role of prostaglandins in the antiarrhythmic effect of ischemic preconditioning (IP) was investigated in pentobarbital-anesthetized rats. In 5 unpreconditioned control rats, 30 min of occlusion of the left coronary artery elicited ventricular tachycardia (VT) and fibrillation (VF), with an average duration of VT and VF of 51 +/- 6 and 43 +/- 4 s, respectively. Frequent ventricular premature beats (VPBs; average 1,249 +/- 145) were also documented in these animals. Thirty minutes of reperfusion after the prolonged coronary occlusion in these animals caused more severe arrhythmias, including irreversible VF. In animals pretreated with IP (n = 5), which was achieved by 3 cycles of 3 min of occlusion followed by 5 min of reperfusion, 30 min of coronary artery occlusion caused neither VT nor VF, but occasional VPBs (average 2 +/- 1, p < 0.001 vs. control). Only occasional VPBs were observed during 30 min of reperfusion in this group. In animals pretreated with indomethacin (1 mg/kg i.v., n = 5) followed by IP, prolonged ischemia and reperfusion led to frequent VPBs but no VT or VF. The average number of VPBs during ischemia and reperfusion in this indomethacin-treated group was less than that of the controls but greater than the IP-only group (p < 0.01). In conclusion, prostaglandins appear to play a role in the protective effect of IP against VPBs during acute ischemia and reperfusion. |
3,712 | Metabolism of preconditioned myocardium: effect of loss and reinstatement of cardioprotection. | Ischemic preconditioning is associated with slower destruction of the adenine nucleotide pool and a slower rate of anaerobic glycolysis during subsequent ischemic stress. Whether this association is causal is uncertain. Using metabolite levels found at baseline and after a 15 min test episode of ischemia, this study tested for concordance, or lack thereof, between the presence or absence of metabolic features v the presence or absence of the preconditioned state. Dogs were assigned to one of four groups: non-preconditioned control (C), full preconditioning (PC) caused by 10 min ischemia (I)+10 min reperfusion (R), dissipated PC (DPC) caused by 10 min I and 180 min R, or reinstated PC in which PC was reinstated in DPC hearts by another 10 min I and 10 min R. At baseline, PC and RPC hearts had a 25% or more decrease in the adenine nucleotide pool (summation operatorAd), a substantial creatine phosphate (CP) overshoot, and a 4-6 times elevation in tissue glucose (G). Of these changes, the decreased summation operatorAd and the CP overshoot persisted during DPC, whereas only G returned to control. Thus, increased G was the only baseline feature, which was concordant with the preconditioned state. The response to ischemic stress in PC and RPC tissue included less lactate production and much less degradation of the summation operatorAd pool to nucleosides and bases than in the C or DPC groups. Thus, slower destruction of the summation operatorAd pool and slower lactate production during ischemia also were concordant with the PC state. The results support the hypothesis that a reduction in energy demand is an essential component of the mechanism of cardioprotection in preconditioned myocardium. However, the mechanism through which ischemic preconditioning results in lower energy demand remains to be established. |
3,713 | Left atrial appendage dysfunction in chronic nonvalvular atrial fibrillation is significantly associated with an elevated level of brain natriuretic peptide and a prothrombotic state. | The study tested the hypothesis that left atrial appendage (LAA) dysfunction in nonvalvular atrial fibrillation (NVAF) correlates with a prothrombotic state, and investigated whether the plasma natriuretic peptides are marker of LAA dysfunction in NVAF. Sixty-seven patients underwent transthoracic and transesophageal echocardiography. The left ventricular fractional shortening, left atrial diameter (LAD), LAA flow velocity and the grade of spontaneous echo contrast (SEC) were determined. The plasma concentrations of atrial natriuretic peptide (ANP), brain natriuretic peptide (BNP), D-dimer, and thrombin-antithrombin III complex (TAT) were measured. The patients were divided into 2 groups according to LAA flow velocity: group I (LAA velocity <20 cm/s) and group II (LAA velocity > or = 20cm/s). The SEC score, D-dimer, TAT, BNP and LAD were significantly increased in group I. Based on simple linear regression analysis, SEC score (r=-0.638), LAD (r=-0.493), D-dimer (r = -0.485), BNP (r = -0.463), TAT (r = -0.455) and age (r = -0.314) were inversely correlated with LAA flow velocity. Multivariate analysis showed that SEC score (p = 0.0014) and plasma BNP level (p=0.0075) were independent negative predictors for LAA flow velocity. In conclusion, LAA dysfunction is associated with a prothrombotic state, and the plasma BNP concentration may serve as a determinant of LAA function in NVAF. |
3,714 | Heart emergency room: effective for both geriatric and younger patients. | To compare the 30-day cardiac event rate between patients aged at least 60 years (geriatric group) with those younger than 60 (younger group), who were enrolled in an Emergency department-based chest pain centre management protocol.</AbstractText>This was a retrospective, cohort study done at the Centre for Emergency Care at the University of Cincinnati, from 1 Oct 1991 to 31 March 1999 (from Oct 1991 to Dec 1998: 9-hour protocol in use; from Jan 1999 to March 1999: 6-hour protocol in use). Patients, at least 25 years, with the chief complaint of non-traumatic chest pain were eligible for management in the unit. Exclusion criteria included acute ST-elevation or depression > 1 mm in 2 contiguous leads, haemodynamic instability or clinical syndrome consistent with unstable angina. Outcomes studied were disposition and cardiac events at 30-days (defined as acute myocardial infarction, congestive heart failure, ventricular fibrillation / tachycardia arrest, coronary artery bypass surgery or percutaneous transluminal coronary angioplasty). The protocol was the standard of care and enrolled patients underwent continuous ECG and ST-segment trend monitoring, serial CK-MB draws at 0, 3, 6 and 9 hours, followed by either a graded exercise stress test or a sestamibi myocardial perfusion scan (from Oct 1998). With the 6-hour protocol the 9-hour draws were omitted and the GXTdone 3 hours earlier.</AbstractText>A total of 2491 patients were enrolled; 304 (12.2%) in the geriatric age-group. The mean age was 66.8+/-5.9 and 41.3+/-8.6 years respectively. There were 133 (43.8%) female patients in the geriatric group and 1170 (53.5%) in the younger group. There were no statistically significant differences between the groups in terms of prevalence of risk factors, but there was significant (p < 0.001) and ECG changes from the baseline (p = 0.0015). The geriatric patients were also not different from the younger ones in terms of GXT positive for ischaemia (10, 5.3% vs 42, 2.7%; p = 0.124), admission rates (61, 20.1% vs 321, 14.7%; p = 0.312), coronary care unit admissions (8, 2.6% vs 63, 2.9%; p = 0.418 and 30-day complication rate (10, 3.6% vs 46, 2.4%; p = 0.303).</AbstractText>The ED-based chest pain unit represents an effective way for the risk-stratification and management of both geriatric and young patients with low-to-moderate risk of acute coronary events.</AbstractText> |
3,715 | Pseudoventricular fibrillation. | A case of atrial fibrillation with asystole was diagnosed as ventricular fibrillation because of the autogain feature of the electrocardiographic monitor. Direct current shock therapy was withheld only because the patient regained consciousness. |
3,716 | Dual-site atrial pacing for atrial fibrillation in patients without bradycardia. | Atrial pacing has been shown to delay the onset of atrial fibrillation (AF) when compared with ventricular pacing in patients with sick sinus syndrome. The role for pacing in the control of AF in patients without bradycardia is uncertain. We performed a randomized, crossover, single-blinded study in 22 patients (14 women, aged 63 +/- 10 years) with paroxysmal AF refractory to treatment with oral sotalol (202 +/- 68 mg/day) and no bradycardic indication for pacing. All patients received a dual-chamber pacemaker with 2 atrial pacing leads positioned at the high right atrium and coronary sinus ostium, respectively. Patients were randomized in a crossover fashion to be paced for 12 weeks, either with high right atrial (RA) pacing at 30 beats/min ("Off") or dual-site RA pacing with an overdrive algorithm that maintained atrial pacing at a rate slightly above the sinus rate ("On"). Treatment on resulted in a significantly higher percentage of atrial pacing and a reduction in atrial ectopic frequency than the treatment off period. The time to the first clinical AF recurrence was prolonged (15 +/- 17 to 50 +/- 35 days, p = 0.006), and total AF burden was reduced (45 +/- 34% vs 22 +/- 29%, p = 0.04) in the on-treatment phase. However, there was no difference in AF checklist symptom scores or overall quality-of-life measures. Dual-site RA pacing with continued sinus overdrive prolonged the time to AF recurrence and decreased AF burden in patients with paroxysmal AF. The absence of a major impact on symptom control suggests that pacing should be used as an adjunctive therapy with other treatment modalities for AF. |
3,717 | Magnetic resonance real-time imaging for the evaluation of left ventricular function. | New ultrafast gradient systems and hybrid imaging sequences make it possible to acquire a complete image in real time, without the need for breathholding or electrocardiogram (ECG) triggering. In 21 patients, left ventricular function was assessed by the use of a turbo-gradient echo technique, an echo-planar imaging (EPI) technique, and a new real-time imaging technique. End-diastolic and end-systolic volumes, left ventricular muscle mass, and ejection fraction of the ultrafast techniques were compared with the turbo-gradient echo technique. Inter- and intraobserver variability was determined for each technique. Image quality was sufficient for automated contour detection in all but two patients in whom foldover occurred in the real-time images. Results of the ultrafast imaging techniques were comparable with conventional turbo-gradient echo techniques. There was a tendency to overestimate the end-diastolic volume by 3.9 and 1.3 ml with EPI real-time imaging, the end-systolic volume by 0.9 and 5.0 ml, and the left ventricular mass by 2.6 and 23.8 g. Ejection fraction showed a tendency to be overestimated by 1.1% with EPI and underestimated by 4.5% with real-time imaging. Correlation between EPI real-time imaging and turbo-gradient echo were 0.94 and O.95, respectively, for end-diastolic volumes, 0.98 and 0.96, respectively, for end-systolic volumes, and 0.96 and 0.89, respectively, for left ventricular mass. Inter- and intraobserver variability was low with all three techniques. Real-time imaging allows an accurate determination of left ventricular function without ECG triggering. Scan times can be reduced significantly with this new technique. Further studies will have to assess the value of real-time imaging for the detection of wall motion abnornmalities and the imaging of patients with atrial fibrillation. |
3,718 | [Ligands of opioid and sigma receptors and correction of cardiac electrical instability in post-infarction cardiosclerosis]. | Peripheral administration of the mu- or kappa-receptor agonists or sigma-receptor antagonists produced a significant receptor-dependent increase in the ventricular fibrillation threshold in rats with postinfarction cardiosclerosis. The effect was not observed upon administration of the epsilon-receptor agonist beta-endorphin. The receptor and molecular mechanisms of the observed effects are discussed. |
3,719 | Epidemiologic evidence of cardiovascular effects of particulate air pollution. | In the past decade researchers have developed a body of epidemiologic evidence showing increased daily cardiovascular mortality and morbidity associated with acute exposures to particulate air pollution. Associations have been found not only with cardiovascular deaths reported on death certificates but also with myocardial infarctions and ventricular fibrillation. Particulate air pollution exposure has been associated with indicators of autonomic function of the heart including increased heart rate, decreased heart rate variability, and increased cardiac arrhythmias. Several markers of increased risk for sudden cardiac death have also been associated with such exposures. These epidemiologic studies provide early guidance to possible pathways of particulate air pollution health effects, which can only be addressed fully in toxicologic and physiologic studies. |
3,720 | Serious cardiac complications during bone marrow transplantation at the University of Minnesota, 1977-1997. | Cardiac complications may result from high-dose chemotherapy or irradiation administered during the conditioning phase of bone marrow and blood stem cell transplantation (BMT). To assess the frequency of clinically serious cardiac toxicity related to the acute phase of BMT, we retrospectively examined life-threatening or fatal cardiotoxicity identified using the complications records of our transplant center clinical database. All serious cardiac toxicity events within 100 days of BMT except those attributable to septic shock, pneumonitis or multi-organ failure were reviewed. Of 2821 BMT patients at the University of Minnesota between 1977 and 1997, 26 were identified as having suffered major or fatal (n = 13) cardiotoxicity (0.9%, 19 adults and seven children). Rapidly progressive heart failure resulted in death of 11 patients, one patient had fatal pericardial tamponade, and one had an acute ventricular fibrillation arrest. The remaining 13 patients (50%) had life-threatening cardiotoxicity including four patients with pericardial tamponade and nine patients with cardiac arrhythmias. Overall, we observed that acute, major cardiotoxic events attributable to BMT are uncommon, occurring with a frequency of <1%. These data suggest that with appropriate pre-transplant clinical evaluation, high-dose cyclophosphamide and irradiation in the BMT preparative phase does not result in frequent, clinically relevant short-term cardiac toxicity. |
3,721 | Bench to bedside: resuscitation from prolonged ventricular fibrillation. | Ventricular fibrillation (VF) remains the most common cardiac arrest heart rhythm. Defibrillation is the primary treatment and is very effective if delivered early within a few minutes of onset of VF. However, successful treatment of VF becomes increasingly more difficult when the duration of VF exceeds 4 minutes. Classically, successful cardiac arrest resuscitation has been thought of as simply achieving restoration of spontaneous circulation (ROSC). However, this traditional approach fails to consider the high early post-cardiac arrest mortality and morbidity and ignores the reperfusion injuries, which are manifest in the heart and brain. More recently, resuscitation from cardiac arrest has been divided into two phases; phase I, achieving ROSC, and phase II, treatment of reperfusion injury. The focus in both phases of resuscitation remains the heart and brain, as prolonged VF remains primarily a two-organ disease. These two organs are most sensitive to oxygen and substrate deprivation and account for the vast majority of early post-resuscitation mortality and morbidity. This review focuses first on the initial resuscitation (achieving ROSC) and then on the reperfusion issues affecting the heart and brain. |
3,722 | [Transesophageal electrophysiologic study: utility in the diagnosis of syncope]. | Neurocardiogenic and arrhythmic syncope are very common and may be found in many patients in Emergency Departments or admitted to hospitals. Technologic advances now allow etiologic diagnosis to be determined but the importance of a detailed clinical history and physical examination can not be overemphasized in the evaluation of syncope, thereby to avoid some costly or invasive procedures. The recent introduction of the head-up tilt test alone or in combination with electrophysiologic studies, has significantly improved our ability to diagnose the etiology of syncope in many cases. Suspicion of an arrhythmic cause of syncope does not always require an invasive electrophysiologic study since the transesophageal electrophysiologic study is useful and provides a high diagnostic yield in the evaluation of non ventricular arrhythmic syncope, such as in the sick sinus syndrome, atrio-ventricular block or in supraventricular tachycardia and for the study of atrial stability. The transesophageal electrophysiologic study is an inexpensive non invasive procedure which does not require complex hospitalary installations. |
3,723 | A short-time multifractal approach for arrhythmia detection based on fuzzy neural network. | We have proposed the notion of short-time multifractality and used it to develop a novel approach for arrhythmia detection. Cardiac rhythms are characterized by short-time generalized dimensions (STGDs), and different kinds of arrhythmias are discriminated using a neural network. To advance the accuracy of classification, a new fuzzy Kohonen network, which overcomes the shortcomings of the classical algorithm, is presented. In our paper, the potential of our method for clinical uses and real-time detection was examined using 180 electrocardiogram records [60 atrial fibrillation, 60 ventricular fibrillation, and 60 ventricular tachycardia]. The proposed algorithm has achieved high accuracy (more than 97%) and is computationally fast in detection. |
3,724 | Variation in the dominant period during ventricular fibrillation. | Time-varying periodicities are commonly observed in biological time series. In this paper, we discuss three different algorithms to detect and quantify change in periodicity. Each technique uses a sliding window to estimate periodic components in short subseries of a longer recording. The three techniques we utilize are based on: 1) standard Fourier spectral estimation; 2) an information theoretic adaption of linear (autoregressive) modeling; and 3) geometric properties of the embedded time series. We compare the results obtained from each of these methods using artificial data and experimental data from swine ventricular fibrillation (VF). Spectral estimates have previously been applied to VF time series to show a time-dependent trend in the dominant frequency. We confirm this result by showing that the dominant period of VF, following onset, first decreases to a minimum and then rises to a plateau. Furthermore, our algorithms detect longer period correlations which may indicate the presence of additional periodic oscillations or more complex nonlinear structure. We show that in general this possibly nonlinear structure is most apparent immediately after the onset of VF. |
3,725 | Acute renal failure after successful cardiopulmonary resuscitation. | To assess the frequency and independent predictors of severe acute renal failure in patients resuscitated from out-of-hospital ventricular fibrillation cardiac arrest.</AbstractText>A cohort study with a minimum follow-up of 6 months.</AbstractText>Emergency department of a tertiary care 2200-bed university hospital.</AbstractText>Consecutive adult (> 18 years) patients admitted from 1 July 1991 to 31 October 1997 after witnessed ventricular fibrillation out-of-hospital cardiac arrest and successful resuscitation.</AbstractText>Acute renal failure was defined as a 25% decrease of creatinine clearance within 24 h after admission. Out of 187 eligible patients (median age 57 years, 146 male), acute renal failure occurred in 22 patients (12%); in 4 patients (18%) renal replacement therapy was performed. Congestive heart failure (OR 6.0, 95% CI 1.6-21.7; p = 0.007), history of hypertension (OR 4.4, 95% CI 1.3-14.7; p = 0.02) and total dose of epinephrine administered (OR 1.1, 95% CI 1.0-1.2; p = 0.009) were independent predictors of acute renal failure. Duration of cardiac arrest, pre-existing impaired renal function and blood pressure at admission were not independently associated with renal outcome.</AbstractText>Severe progressive acute renal failure after cardiopulmonary resuscitation (CPR) is rare. Pre-existing haemodynamics seem to be more important for the occurrence of acute renal failure than actual hypoperfusion during resuscitation.</AbstractText> |
3,726 | [Right ventricular heart failure in hyperthyroidism]. | Cardiovascular disorders in patients affected with hyperthyroidism are very common; the increase in the heart rate and in inotropism combines with a rise in the cardiac index towards which the reduction in peripheral resistances and an increase in the venous return to the heart contribute. The increase in myocardial excitabi1ity, caused above all by triiodothyronine, may be attended with atrial extrasystoles or even with atrial fibrillation. Congestive heart failure during hyperthyroidism, even if rare, may either reveal itself in association with pre-existent cardiopathy or to be precipitated by tachyar-rhythrmia, particu1arly, by paroxysmal atrial fibrillation. The case is described of a young woman affected with Graves' disease, presenting an ingravescent dyspnoea, in which sinusal tachycardia, the S1Q3 electrocardiographic figure and the echocardiographic reports of a right ventricu1ar overload with pulmonary hypertension and systemic venous congestion, suggest picture of acute pulmonary embolism. The isolated dysfunction of the right ventricle resolved quickly after an adequate antithyroid therapy. The oddness of presentation of Graves' disease in this case would suggest the execution of the thyroid profile for all patients with a primary diagnosis of heart failure, in order to single out hyperthyroid subjects with reversible myocardial dysfunction. |
3,727 | Predictors of atrial flutter with 1:1 conduction in patients treated with class I antiarrhythmic drugs for atrial tachyarrhythmias. | The purpose of the study was to look for the predictor factors of atrial proarrhythmic effects of class I antiarrhythmic drugs.</AbstractText>Class I antiarrhythmic drugs may induce or exacerbate cardiac arrhythmias. The predictors of ventricular proarrhythmia are known. The predictors of atrial flutter with 1:1 conduction are unknown.</AbstractText>Clinical history, EGG, signal-averaged EGG (SAECG) and electrophysiologic study were analysed in 24 cases of 1:1 atrial flutter with class I AA drugs and in 100 control patients without history of 1:1 atrial flutter with class I AA drugs.</AbstractText>The ages of patients varied from 46 to 78 years. Underlying heart disease was present in nine patients. The surface EGG revealed the presence of a short PR interval (PR<0.13 ms), visible in leads V5, V6 in eight (35%) patients with normal P wave duration; in other patients with prolonged P wave duration, PR seemed normaL On SAECG recording, there was a pseudofusion between P wave and QRS complex. The electrophysiologic study revealed some signs indicating a rapid AV nodal conduction (short AH interval or rate of 2nd degree AV block at atrial pacing >200 beats/mm) in 19 of the 23 studied patients. All patients, except one, had at least one sign indicating a rapid AV nodal conduction (short PR and/or P wave-QRS complex continuity on SAECG). In the control group, seven patients (7%) had a short PR interval (P<0.01) and 11 (11%) had a pseudofusion between P wave and QRS complex on SAECG (P<0.001). The P wave-QRS complex pseudofusion on SAECG had a sensitivity of 100% and a specificity of 89% for the prediction of an atrial proarrhythmic effect with class I antiarrhythmic drug.</AbstractText>We recommend avoiding class I AA drugs in patients with a short PR interval on surface EGG and to record SAECG in those with apparently normal PR interval to detect a continuity between P wave and QRS complex, which could indicate a rapid AV nodal conduction, predisposing to 1:1 atrial flutter with the drug.</AbstractText> |
3,728 | Pathological analysis of myocardial cell under ventricular tachycardia and fibrillation based on symbolic dynamics. | Ventricular fibrillation (VF) is one of the most serious malignant arrhythmias usually resulting from immediate degeneration of ventricular tachycardia (VT). In order to analyse the nonlinear dynamics of the cardiac micro-mechanism under VT and VT rhythm, at the cellular level, myocardial cell action potentials are investigated under different rhythm, normal sinus rhythm, VT and VT. On the basis of nonlinear chaotic theory and symbolic dynamics, we put forward new definitions, complexity rate, etc, and obtained some useful properties for cellular electrophysiological analysis. The results of the experiments and computation show that the myocardial cellular signals under VT and VF rhythm are different kinds of chaotic signals in that the cardiac chaos attractor under VF is higher than that under VT. The analytical complexity theory has been promising in the clinical application. |
3,729 | Initial experience with single lead intracardial cardioversion for refractory atrial fibrillation. | Chronic atrial fibrillation (AF) is a common arrhythmia, associated with a substantial morbidity (thromboemboli, worsening left ventricular function). Established therapy for pharmacological refractory AF is high-energy trans-thoracic electric cardioversion (TTCV), but this strategy is ineffective for 10-30% of the patients. The purpose of the present study is to establish the safety and efficacy of low-energy intracardiac cardioversion (ICCV) with a relatively new balloon-guided single-catheter system with dual chamber pacing possibility for this group of patients.</AbstractText>Patients in whom an attempt to restore sinus rhythm (SR) by TTCV under antiarrhythmic therapy failed were eligible for the study. For the ICCV-attempt, a single flow-guided atrial cardioversion catheter was used. Low-energy biphasic shocks of increasing energy (6-15 J) were delivered, if necessary in combination with intravenous amiodarone, until SR was restored. In case of early recurrence of AF, another attempt was made with immediate post-shock overdrive pacing (AOO) in order to suppress premature atrial activity.</AbstractText>Initially, 14 of the 16 treated patients (90%) were converted to SR successfully. In eight patients additional amiodarone i.v. was administered and in six patients atrial overpacing was used after ICCV. In seven and five patients, respectively, these strategies were successful. Long-term follow-up (1-3 months) showed that in nine patients (56%) SR was preserved; eight of them on oral amiodarone. No adverse events were seen during the procedure and follow-up, especially no bleedings, despite puncturing under adequate anticoagulation therapy.</AbstractText>ICCV using a single atrial cardioversion catheter is a safe and effective method to restore SR in patients in whom TTCV failed previously. Long-term follow-up of this procedure is comparable to that of other studies. Results are influenced by antiarrhythmic drug therapy, compliance and patient selection.</AbstractText> |
3,730 | What is cardiac resynchronization therapy? | Cardiac resynchronization refers to pacing techniques that change the degree of atrial and ventricular electromechanical asynchrony in patients with major atrial and ventricular conduction disorders. Atrial and ventricular resynchronization is usually accomplished by pacing from more than one site in an electrical chamber--atrium or ventricle--and occasionally by stimulation at a single unconventional site. Resynchronization produces beneficial hemodynamic and antiarrhythmic effects by providing a more physiologic pattern of depolarization. Atrial resynchronization may prevent atrial fibrillation in selected patients with underlying bradycardia or interatrial block. Its antiarrhythmic effect in the absence of bradycardia is unclear. Ventricular resynchronization is of far greater clinical value than atrial resynchronization. Biventricular (or single-chamber left ventricular) pacing is beneficial for patients with congestive heart failure, severe left ventricular systolic dysfunction, dilated cardiomyopathy (either ischemic or idiopathic), and a major left-sided intraventricular conduction disorder, such as left bundle branch block. The change in electrical activation from resynchronization, which has no positive inotropic effect as such, is translated into mechanical improvement with a more coordinated left ventricular contraction. Several recent randomized trials and a number of observational studies have demonstrated the long-term effectiveness of ventricular resynchronization in the above group of patients. The high incidence of sudden death among these patients has encouraged ongoing clinical trials to evaluate the benefit of a system that combines biventricular pacing and cardioversion-defibrillation into a single implantable device. |
3,731 | Report of a life-threatening arrhythmia after hospital discharge in a liver transplant recipient with previously unknown congenital long QT syndrome. | The long QT syndrome affects heart rhythm by prolonging ventricular repolarisation; it is potentially life-threatening since it can evolve into torsades de pointes (a polymorphic ventricular tachycardia) and/or ventricular fibrillation. The case is presented of a 55-year-old liver transplant recipient with a genetically determined long QT syndrome not detected by the standard preoperative cardiological evaluation. It was mild in the immediate post-operative period but developed into torsades de pointes after discharge, probably as a result of therapy. This case was particularly challenging because the first arrhythmic episodes were short and electocardiographically silent, and thus the related faints were thought to have a neurological basis. When the true cause emerged during a monitored episode of torsades de pointes, electric defibrillation was used to restore sinus rhythm and isoproterenol administered to increase heart rate and thus shorten the prolonged QT interval Long-term control was obtained by means of an implantable intracardiac defibrillator. In orthotopic liver transplant recipients with long QT syndrome, particular attention should be given to post-operative therapy as some routinely used drugs can trigger life-threatening ventricular arrhythmias. |
3,732 | Potassium status of Northeast Thai constructors in three different geographic locations. | Sudden and unexpected death of young adults during sleep is a phenomenon among Southeast Asians and particularly young Northeast (NE) Thailand constructors in Singapore. Survivor of sudden unexplained death syndrome (SUDS) without structural heart disease with idopathic ventricular fibrillation (VF) has been documented. Low plasma potassium (K) and depletion of K can occur simply through a reduction of K intake and are associated with increased risk of VF. The K-status of the populations was evaluated in the NE (Group 1, n=30), Bangkok (Group 2, n=48) and Singapore (Group 3, n=46). Groups 2 and 3 were further subdivided into Group 2A (worked in Bangkok < or = 1 year, n=8), Group 2B (worked in Bangkok > 1 year, n=40), Group 3A (consumed self-prepared or ready-to-buy meals, n=25) and Group 3B (regularly consumed foods provided free-of-charge by construction companies, n=21). Thirty-four male healthy university personnels from the NE and Bangkok served as the control--Group 4. Two 24-h urine samples and a fasting blood sample were collected from each subject. Dietary-K from food was determined by duplicated meal analysis. All these samples were then analyzed for their K-content. Group 3A had the lowest K-status: their K-intake, serum-K, and urinary-K level were 29 +/- 5.8 mmol/day (% low K-intake=100), 3.43 +/- 0.34 mmol/L (% hypokalemia=48) and 19.23 +/- 8.2 mmol/day (% hypokaliuria=87.5), respectively. Among the construction workers, average K-intake, serum-K and urinary-K levels were 45.5 +/- 6.1 mmol/day (% low K-intake = 37.5), 3.93 +/- 0.2 mmol/L (% hypokalemia = 2.5) and 39.6 +/- 9.2 mmol/day (% hypokaliuria = 12.5), respectively. The values of Group 2B were similar to Group 4. In addition, when the data from all of the groups were compared, there was a positive correlation between dietary-K (intake) and urinary-K (excretion) (r=0.881, p<0.001). In conclusion, NE Thailand constructors from various locations exhibited low K status with low dietary-K, high incidence of hypokalemia, and low urinary-K. From the present study, this low K status may be an important trigger factor for VF in construction workers and associated with increase risk of SUDS. |
3,733 | From genes to whole organs: connecting biochemistry to physiology. | The successful analysis of physiological processes requires quantitative understanding of the functional interactions between the key components of cells, organs and systems, and how these interactions change in disease states. This information does not reside in the genome, or even in the individual proteins that genes code for. There is therefore no alternative to copying nature and computing these interactions to determine the logic of healthy and diseased states. The rapid growth in biological databases, models of cells, tissues and organs, and in computing power has made it possible to explore functionality all the way from the level of genes to whole organs and systems. Examples are given of genetic modifications of the Na+ channel protein in the heart that predispose people to ventricular fibrillation, and of multiple target therapy in drug development. Complexity in biological systems also arises from tissue and organ geometry. This is illustrated using modelling of the whole heart. |
3,734 | Prevalence of left atrial chamber and appendage thrombi in patients with atrial flutter and its clinical significance. | The study was done to assess the prevalence of left atrial (LA) chamber and appendage thrombi in patients with atrial flutter (AFl) scheduled for electrophysiologic study (EPS), to evaluate the prevalence of thromboembolic complications after transesophageal echocardiographic (TEE)-guided restoration of sinus rhythm and to evaluate clinical risk factors for a thrombogenic milieu.</AbstractText>Recent studies showed controversial results on the prevalence of atrial thrombi and the risk of thromboembolism after restoring sinus rhythm in patients with AFl.</AbstractText>Between 1995 and 1999, patients with AFl who were scheduled for EPS were included in the study. After transesophageal assessment of the left atrial appendage and exclusion of thrombi, an effective anticoagulation was initiated and patients underwent EPS within 24 h.</AbstractText>We performed 202 EPSs (radiofrequency catheter ablation, n = 122; overdrive stimulation, n = 64; electrical cardioversion, n = 16) in 139 consecutive patients with AFl. Fifteen patients with a thrombogenic milieu were identified. All of them had paroxysmal atrial fibrillation (AF). Transesophageal echocardiography revealed LA thrombi in two cases (1%). After EPS no thromboembolic complications were observed. Diabetes mellitus, arterial hypertension and a decreased left ventricular ejection fraction were found to be independent risk factors associated with a thrombogenic milieu.</AbstractText>The findings of a low prevalence of LA appendage thrombi (1%) in patients with AFl and a close correlation between a history of previous embolism and paroxysmal AF support the current guidelines that patients with pure AFl do not require anticoagulation therapy, whereas patients with AFl and paroxysmal AF should receive anticoagulation therapy. In addition, the presence of clinical risk factors should alert the physician to an increased likelihood for a thrombogenic milieu.</AbstractText> |
3,735 | Prevalence and mortality of the Brugada-type electrocardiogram in one city in Japan. | We sought to study the prevalence and mortality of subjects exhibiting the Brugada-type electrocardiogram (ECG) in a community-based population in Japan.</AbstractText>The Brugada syndrome has been associated with sudden death in subjects without structural heart disease. Hospital-based studies showed 11% to 38% annual fatal arrhythmic events in patients with the Brugada syndrome.</AbstractText>Prevalence and mortality of the Brugada-type ECG were studied in subjects who had ECGs during a health examination in Moriguchi, Osaka, Japan. Information about death and relocation from Moriguchi city was obtained prospectively.</AbstractText>The Brugada-type ECG was found in 98 of 13,929 study subjects (0.70%, 95% confidence interval [CI]: 0.57% to 0.86%). The typical coved-type with an rsR' pattern in V(1) lead ("typical" Brugada-type) was found in 0.12% of subjects (95% CI: 0.07% to 0.20%). The prevalence for male subjects with the Brugada-type ECG (81%) was significantly higher than it was for those without (26%, p < 0.0001). In male subjects, the Brugada-type ECG was found in 2.14% (95% CI: 1.70% to 2.66%), and the "typical" Brugada-type was found in 0.38% (95% CI: 0.21% to 0.64%). After 2.6 +/- 0.3 years of follow-up, there was 1 death (1.0%, 95% CI: 0.03% to 5.6%) of a subject with the Brugada-type ECG, whereas there were 139 deaths (1.0%, 95% CI: 0.85% to 1.2%) of those without the Brugada-type ECG (p = 0.9943, log-rank test).</AbstractText>A substantial number of the Brugada-type ECG were observed in subjects in a community-based population in Japan, especially in men. The total mortality of subjects with the Brugada-type ECG did not differ from the mortality of those without the Brugada-type ECG in a community-based population.</AbstractText> |
3,736 | The prevalence, incidence and prognostic value of the Brugada-type electrocardiogram: a population-based study of four decades. | We sought to demonstrate the prevalence, incidence and prognostic value of the Brugada-type electrocardiogram (ECG) in a general population.</AbstractText>The Brugada syndrome is characterized by evidence of right bundle branch block and ST segment elevation in the right precordial leads, as well as sudden death caused by ventricular fibrillation. However, the natural history of the Brugada-type ECG remains unclear.</AbstractText>We investigated 4,788 subjects (1,956 men and 2,832 women) who were <50 years old in 1958 and had undergone biennial health examinations, including electrocardiography, through 1999. The Brugada-type ECG was defined as a terminal r' wave in lead V(1) and ST segment elevation > or =0.1 mV in leads V(1) and V(2). Unexpected death was defined as sudden death or unexplained accidental death.</AbstractText>There were a total of 32 Brugada-type ECG cases; the prevalence and incidence were 146.2 in 100,000 persons and 14.2 persons per 100,000 person-years, respectively. The incidence was nine times higher among men than women, and the average age at presentation was 45 +/- 10.5 years. The Brugada-type ECG appeared intermittently in most cases and was found in 26% of subjects who died unexpectedly. Cox survival analysis revealed that mortality from unexpected death was significantly higher in subjects with a Brugada-type ECG than in control subjects (p < 0.01). Unexpected deaths were more frequent among subjects with the Brugada-type ECG who had a history of syncope (p < 0.05).</AbstractText>The Brugada-type ECG is not a very rare condition in the adult Japanese population. Subjects with a Brugada-type ECG have an increased risk of unexpected death.</AbstractText> |
3,737 | Acute toxicities of betel nut: rare but probably overlooked events. | Betel nut chewing has long been a social habit in Taiwan and other Asian and tropical countries. It produces various autonomic and psychoneurologic effects including tachycardia, flushing, warmth, cholinergic activation, alertness, and euphoria. Although the oral carcinogenic effects are well known, data concerning its acute toxicity are few. To better understand the toxicity of betel nut, cases reported to the Taiwan Poison Control Center as probable or possible betel nut-related toxicity (January 1988-June 1998) were reviewed. In the 17 cases suitable for review (14 males, 3 females, age 21 to 60 years), the most common manifestations were tachycardia/palpitations (7); tachypnea/dyspnea (6); hypotension and sweating (5); vomiting, dizziness, and chest discomfort (4); abdominal colic, nausea, numbness, and coma (3); and acute myocardial infarction and related manifestations (2). The reported quantity of betel nut used was low (1 to 6 nuts), except an extract of 100 betel nuts was used in 1 case and 66 chewed in another. Most cases recovered within 24 hours after the exposure. One patient developed probable acute myocardial infarction and ventricular fibrillation and died despite repeated cardiac defibrillation. Although betel nut chewing is widespread, significant toxicity as reported to a poison center is rare. Because most betel nut-related effects are transient and mild in nature, the incidence of such events is likely to be underreported. Nevertheless, betel nut chewing can produce significant cholinergic, neurological, cardiovascular, and gastrointestinal manifestations. It is possible that it may aggravate cardiac diseases in susceptible patients but this hypothesis must be further investigated. Treatment is symptomatic. With timely support, rapid and complete recovery is anticipated but a small risk of major complications cannot yet be discounted. |
3,738 | Antiarrhythmic drug use in the implantable defibrillator arm of the Antiarrhythmics Versus Implantable Defibrillators (AVID) Study. | Previous retrospective or observational series suggest that many patients with an implantable cardioverter-defibrillator (ICD) will be treated with antiarrhythmic drugs (AADs) to modify the frequency or manifestation of recurrent ventricular arrhythmias. The relative clinical benefit, however, is uncertain, and deleterious interactions can occur. The objective of this clinical investigation was to study the need for, and effects of, concomitant AAD use with the ICD in a prospectively defined cohort.</AbstractText>All patients randomly assigned to the ICD arm of the Antiarrhythmics Versus Implantable Defibrillators (AVID) study were followed for the addition of class I or III AADs ("crossover") after hospital discharge. Addition of AADs was strictly regulated by AVID protocol. The timing and reasons for crossover and the effects on ventricular arrhythmia recurrence were analyzed. Patients were excluded if they required AADs before hospital discharge after index arrhythmias or if they had no ventricular arrhythmia before initiation of AADs.</AbstractText>After a median follow-up of 135 days, 81 (18%) of the 461 eligible patients required AADs and formed the crossover group. The primary reason for crossover was frequent ICD shocks in 64% of patients. The most common AAD selected was amiodarone (in 42%). Independent predictors of crossover were lower ejection fraction, absence of ventricular fibrillation, or presence of nonsyncopal ventricular tachycardia at presentation, prior unexplained syncope, female sex, and history of cigarette smoking. Before AAD use, the 1-year arrhythmia event rate was 90%; after AAD, the event rate was only 64% (P =.0001). The time to first event was extended from 3.9 +/- 0.7 months to 11.2 +/- 1.8 months. There were 1.4 +/- 3.7 fewer ICD therapy events (P =.005) after crossover, predominantly accounted for by reduction in shocks rather than antitachycardia pacing therapies.</AbstractText>The majority of patients who receive ICDs for sustained ventricular tachycardia or ventricular fibrillation can be treated without AADs. Most commonly, AADs are added to combat frequent ICD shocks, which are successfully reduced by AAD therapy.</AbstractText> |
3,739 | Effect of carvedilol on survival and hemodynamics in patients with atrial fibrillation and left ventricular dysfunction: retrospective analysis of the US Carvedilol Heart Failure Trials Program. | Atrial fibrillation (AF) is present in a significant number of patients with congestive heart failure (CHF) caused by left ventricular dysfunction and is associated with significant morbidity and increased mortality rates. Thus it is necessary to establish therapy to improve the outcome in this high-risk population.</AbstractText>We conducted a retrospective analysis of data from the US Carvedilol Heart Failure Trials Program and identified patients with AF at the time of enrollment. In these trials, 1094 patients with at least 3 months of heart failure symptoms and an ejection fraction < or = 0.35 were randomly assigned to receive carvedilol or placebo in a double-blind, stratified program according to performance on an exercise test.</AbstractText>One hundred thirty-six patients with concomitant AF and CHF were identified during the screening visit (84 assigned to carvedilol and 52 to placebo). Therapy with carvedilol resulted in a significant improvement in left ventricular ejection fraction (from 23% to 33% with carvedilol and from 24% to 27% with placebo, P =.001). The physician global assessment improved in a greater number of patients treated with carvedilol than in those treated with placebo (71% vs 48%, P =.025). A trend toward a reduction in the combined end point of death or CHF hospitalization was also observed (19% in patients treated with placebo and 7% in patients on carvedilol; relative risk, 0.35; 95% confidence interval, 0.12, 1.02; P =.055).</AbstractText>In patients with AF complicating CHF, carvedilol significantly improves left ventricular ejection fraction and physician global assessment and probably reduces the combined end point of CHF hospitalizations or death.</AbstractText> |
3,740 | Treatment of congestive heart failure--current status of use of digitoxin. | Digitalis glycosides exert a positive inotropic effect, i.e. an increase in myocardial contractility associated with a prolongation of relaxation period, and glycosides lower the heart rate (negative chronotropic), impede stimulus conduction (negative dromotropic) and promote myocardial excitability (positive bathmotropic). They seem to influence the activities of both the vagal and the sympathetic systems. Digitalis glycosides that belong to different substance classes are closely comparable concerning pharmacodynamics but differ substantially in regard to pharmacokinetics. Digoxin and its derivatives are less lipophilic, show lower protein binding and shorter half-life, are mainly eliminated via the kidney and accumulate rather rapidly in cases of insufficient kidney function. Digitoxin is highly lipophilic and extensively bound to plasma proteins, has a longer half-life, is mainly eliminated in the metabolized state via urine and faeces and does not accumulate in kidney dysfunction. As a result of a more stable pharmacokinetic profile, the incidence of toxic side effects seems to be lower with digitoxin than with digoxin. Since the beginning of the 1990s, the antagonists of the RAAS qualified as the standard treatment for congestive heart failure, often in combination with diuretics, vasodilators or beta-antagonists. However, the important role of digitalis glycosides as therapeutic comedication or alternative was never denied, especially in atrial fibrillation with tachycardia. The PROVED and RADIANCE trials proved a detrimental effect of the withdrawal of digoxin therapy on exercise capacity, left-ventricular ejection fraction and clinical symptoms. The DIG trial revealed that digoxin comedication in sinus rhythm patients with congestive heart failure was associated with a lower morbidity (as taken from death or hospitalization because of worsening heart failure) and an unchanged overall mortality--being a unique feature among the available inotropic drugs. Comparable studies for digitoxin have not yet been performed but, because of its higher pharmacological stability, it might well be associated with even more advantages in this regard than digoxin. |
3,741 | [Complications of stress echocardiography]. | Stress echocardiography is an established clinical testing method and is accurate for the detection of coronary artery disease. Despite its widespread use, the safety of stress echocardiography has not been sufficiently documented in Japanese laboratories.</AbstractText>The feasibility, safety, complications and side effects of stress echocardiography were assessed for detecting myocardial ischemia in patients with suspected coronary artery disease.</AbstractText>1,866 patients who underwent dobutamine echocardiography(n = 897), exercise echocardiography(n = 722), and dipyridamole echocardiography(n = 247) were prospectively studied from November 1990 to April 2000. Dobutamine was administered intravenously at 5, 10, 20, 30, 40 micrograms/kg/min in 3-minute intervals. Exercise echocardiography used the supine ergometer, starting at 50 W and increasing gradually by 25 W at 3-minute intervals to the maximum of 150 W. Dipyridamole was administered intravenously at 0.14 mg/kg/min for 4 min. After a 4-minute observation period, the drug was re-administered at the same dose for 2 min.</AbstractText>The most common side effects under each stress were ventricular premature beats in 34.1% (dobutamine echocardiography), ventricular premature beats in 14.4%(exercise), and headache in 24.3% (dipyridamole). Serious side effects occurred in one patient(0.05%). The case of acute myocardial infarction was caused by dipyridamole echocardiography, and the patient needed emergency coronary angioplasty. Seven patients needed other drug therapy for nonsustained ventricular tachycardia(one), paroxysmal supraventricular tachycardia(two), sinus bradycardia(three), and bronchial asthma(one). There was no incidence of death, shock, or ventricular fibrillation, sustained ventricular tachycardia or other conditions requiring inpatient observation during stress echocardiography.</AbstractText>Stress echocardiography is a reasonable, safe method for determining myocardial ischemia, but may be associated with minor, self-limiting side effects.</AbstractText> |
3,742 | Performance and error analysis of automated external defibrillator use in the out-of-hospital setting. | We determined whether automated external defibrillators (AEDs) can meet the American Heart Association performance criteria to detect and shock unstable cardiac rhythms (ventricular fibrillation [VF], ventricular tachycardia [VT]) in the setting of an out-of-hospital cardiac arrest.</AbstractText>AED performance was reviewed for cardiac arrests occurring between January 1, 1995, and December 31, 1997. After every cardiac arrest, data regarding each rhythm analyzed and subsequent response (shock or no shock) were downloaded from the AED memory module. The study paramedic and study physician independently reviewed each case and interpreted cardiac rhythms from downloaded AED data. The emergency medical services medical director resolved all discrepancies in a blinded manner. All cases of out-of-hospital cardiac arrest in which an AED was turned on and a rhythm analyzed were included. The primary objective was the correct identification and defibrillation of VF or VT. Sensitivity, specificity, and predictive values with 95% confidence intervals (CIs) were calculated. Sources of error in AED rhythm management are also described.</AbstractText>A total of 3,448 AED rhythms were available for interpretation. Sensitivity and specificity for appropriate AED management of a shockable (VF or VT) rhythm were 81.0% (95% CI 77.9% to 83.8%) and 99.9% (95% CI 99.7% to 100%), respectively. Positive and negative predictive values were 99.6% (95% CI 98.7% to 99.9%) and 95.5% (95% CI 94.7% to 96.2%), respectively. There were 132 errors associated with AED management. Two errors resulted in delivery of an inappropriate shock. In the remaining 130 errors, a shockable rhythm was not shocked. Fifty-five (42.3%) errors were AED dependent, 70 (53.9%) were operator dependent, and 5 (3.9%) were unclassified.</AbstractText>The AED had high specificity and moderately high sensitivity in detecting and shocking unstable cardiac rhythms in the out-of-hospital setting. Few cardiac rhythms were mismanaged by the AED. Elimination of operator-dependent errors could increase AED sensitivity.</AbstractText> |
3,743 | Out-of-hospital defibrillation with automated external defibrillators: postshock analysis should be delayed. | The American Heart Association protocols for use of automated external defibrillators (AEDs) recommend that a rhythm analysis be done immediately after each defibrillation attempt. However, shock is often followed by electrical silence or marginally organized electrical activity before ventricular fibrillation (VF) or ventricular tachycardia (VT) recurs. The optimal timing of postshock analysis for identification of recurrent VF/VT is unknown. This study examines the time to recurrence of VF/VT after a defibrillation attempt with AED.</AbstractText>Over an 18-month period, all tapes from patients with out-of-hospital cardiac arrest who received shocks at least once with an AED were screened for recurrent VF/VT. All cases come from a single emergency medical services system providing basic life support, defibrillation with AED, and intubation with an esophageal-tracheal twin-lumen airway device (Combitube) for a population of 633,511 individuals. Pediatric and traumatic cases were excluded. When VF/VT recurred within 3 minutes of the defibrillation attempt, rhythm strips were printed and included in the study. Two cardiology fellows, blinded to the study objectives, measured the time from defibrillation to recurrent VF/VT for each strip.</AbstractText>Over the study period, 222 tapes from 96 patients met the inclusion criteria. Only 44 (20%) occurrences of VF/VT had recurred within 6 seconds of defibrillation, 162 (73%) at 60 seconds, and 200 (90%) at 90 seconds.</AbstractText>Eighty percent of VF/VT recurred more than 6 seconds after defibrillation and were missed when using current American Heart Association AED protocols. Subsequent analysis should be postponed until at least 30 seconds after defibrillation. Performing 30 seconds of chest compressions after defibrillation before subsequent AED rhythm analysis would increase AED identification of VF/VT to 52%.</AbstractText> |
3,744 | Electrophysiologic basis by which epinephrine facilitates defibrillation after prolonged episodes of ventricular fibrillation. | Even though epinephrine has been shown to decrease the electrical stability of the heart, it is used extensively in cardiac resuscitation. The objective of this study is to document electrophysiologic parameters of epinephrine, which would facilitate defibrillation.</AbstractText>In 20 swine, electrically induced ventricular fibrillation was allowed to continue for 10 minutes. Animals were then randomly assigned to receive either intracardiac injection of 1 mg of epinephrine or 10 mL of normal saline solution. Synchronization and dispersion of the repolarization of fibrillatory waves and cycle length were measured.</AbstractText>As the ventricular fibrillation continued, cycle length was prolonged, and synchronization and dispersion deteriorated. With epinephrine, cycle length shortened from 416+/-21 to 204+/-23 ms (P<.005), synchronization improved from 114+/-13 to 61+/-10 ms (P<.05), and dispersion narrowed from 84+/-10 to 49+/-8 ms (P<.005). Normal saline solution had no effect. Successful resuscitation was achieved in all 10 animals administered epinephrine and only 1 animal in the saline solution group.</AbstractText>Epinephrine's effect on cycle length, synchronization, and dispersion of repolarization of fibrillatory waves may be the mechanism with which it facilitates defibrillation.</AbstractText> |
3,745 | Atrial therapies reduce atrial arrhythmia burden in defibrillator patients. | Approximately 25% of patients who receive an implantable cardioverter-defibrillator (ICD) to treat ventricular tachyarrhythmias have documented atrial tachyarrhythmias before implantation. This study assessed the ability of device-based prevention and termination therapies to reduce the burden of spontaneous atrial tachyarrhythmias.</AbstractText>Patients with a standard indication for the implantation of an ICD and 2 episodes of atrial tachyarrhythmias in the preceding year received a dual-chamber ICD (Medtronic 7250 Jewel AF) that uses pacing and shock therapies for prevention and/or termination of atrial tachyarrhythmias. In a multicenter trial, patients were randomized to 3-month periods with atrial therapies "on" or "off" and subsequently crossed over. Analysis was performed on the 52 of 269 patients who had episodes of atrial tachyarrhythmia and had >/=30 days of follow-up with atrial therapies on and off. The atrial therapies resulted in a reduction of atrial tachyarrhythmia burden from a mean of 58.5 to 7.8 h/mo. A paired analysis (Wilcoxon signed-rank test) showed that the median difference in burden (1.1 h/mo) was highly significant (P=0.007). When the subgroup of 41 patients treated only with atrial pacing therapies was analyzed, the reduction in burden persisted (P=0.01).</AbstractText>In this study, patients with a standard ICD indication and atrial tachyarrhythmias had a significant reduction in atrial tachyarrhythmia burden with use of atrial pacing and shock therapies.</AbstractText> |
3,746 | The efficacy of epinephrine or vasopressin for resuscitation during epidural anesthesia. | Cardiopulmonary resuscitation (CPR) during epidural anesthesia is considered difficult because of diminished coronary perfusion pressure. The efficacy of epinephrine and vasopressin in this setting is unknown. Therefore, we designed this study to assess the effects of epinephrine versus vasopressin on coronary perfusion pressure in a porcine model with and without epidural anesthesia and subsequent cardiac arrest. Thirty minutes before induction of cardiac arrest, 16 pigs received epidural anesthesia with bupivacaine while another 12 pigs received only saline administration epidurally. After 1 min of untreated ventricular fibrillation, followed by 3 min of basic life-support CPR, Epidural Animals and Control Animals randomly received every 5 min either epinephrine (45, 45, and 200 microg/kg) or vasopressin (0.4, 0.4, and 0.8 U/kg). During basic life-support CPR, mean +/- SEM coronary perfusion pressure was significantly lower after epidural bupivacaine than after epidural saline (13 +/- 1 vs 24 +/- 2 mm Hg, P < 0.05). Ninety seconds after the first drug administration, epinephrine increased coronary perfusion pressure significantly less than vasopressin in control animals without epidural block (42 +/- 2 vs 57 +/- 5 mm Hg, P < 0.05), but comparably to vasopressin after epidural block (45 +/- 4 vs 48 +/- 6 mm Hg). Defibrillation was attempted after 18 min of CPR. After return of spontaneous circulation, bradycardia required treatment in animals receiving vasopressin, especially with epidural anesthesia. Systemic acidosis was increased in animals receiving epinephrine than vasopressin, regardless of presence or absence of epidural anesthesia. We conclude that vasopressin may be a more desirable vasopressor for resuscitation during epidural block because the response to a single dose is longer lasting, and acidosis after multiple doses is less severe compared with epinephrine. |
3,747 | Improving standard cardiopulmonary resuscitation with an inspiratory impedance threshold valve in a porcine model of cardiac arrest. | To improve the efficiency of standard cardiopulmonary resuscitation (CPR), we evaluated the potential value of impeding respiratory gas exchange selectively during the decompression phase of standard CPR in a porcine model of ventricular fibrillation. After 6 min of untreated cardiac arrest, anesthetized farm pigs weighing 30 kg were randomized to be treated with either standard CPR with a sham valve (n = 11) or standard CPR plus a functional inspiratory impedance threshold valve (ITV(TM)) (n = 11). Coronary perfusion pressure (CPP) (diastolic aortic minus right atrial pressure) was the primary endpoint. Vital organ blood flow was assessed with radiolabeled microspheres after 6 min of CPR, and defibrillation was attempted 11 min after starting CPR. After 2 min of CPR, mean +/- SEM CPP was 14 +/- 2 mm Hg with the sham valve versus 20 +/- 2 mm Hg in the ITV group (P < 0.006). Significantly higher CPPs were maintained throughout the study when the ITV was used. After 6 min of CPR, mean +/- SEM left ventricular and global cerebral blood flows were 0.10 +/- 0.03 and 0.19 +/- 0.03 mL. min(-1). g(-1) in the Control group versus 0.19 +/- 0.03 and 0.26 +/- 0.03 mL. min(-1). g(-1) in the ITV group, respectively (P < 0.05). Fifteen minutes after successful defibrillation, 2 of 11 animals were alive in the Control group versus 6 of 11 in the ITV group (not significant). In conclusion, use of an inspiratory impedance valve during standard CPR resulted in a marked increase in CPP and vital organ blood flow after 6 min of cardiac arrest. |
3,748 | Successful prevention of recurrent ventricular fibrillation by intravenous isoproterenol in a patient with Brugada syndrome. | Intravenous administration of isoproterenol restored the ST-segment configuration to nearly normal in the right precordial leads and completely prevented spontaneous VF attacks in a patient with Brugada syndrome. The formation of a Brugada-type ECG has been attributed to the transmural dispersion of repolarization of the right ventricular epicardium and related to modulation of the autonomic nervous system. Our case may provide clues to the pathophysiological mechanism of this syndrome. |
3,749 | Washing machine associated 50 Hz detected as ventricular fibrillation by an implanted cardioverter defibrillator. | This case report describes a patient with an automatic ICD who suffered a defibrillation shock without warning symptoms. An electrical interference can be observed in the stored EGM of the episode. The patient explained that the moment he felt the shock he was touching a washing machine. After correct grounding of this machine the patient did not suffer more inappropriate shocks. |
3,750 | Increased levels of tissue plasminogen activator antigen and factor VIII activity in nonvalvular atrial fibrillation: relation to predictors of thromboembolism. | Given that nonvalvular atrial fibrillation (AF)-associated stroke can be either cardioembolic or atherothrombotic, we investigated the relationships between nonvalvular AF and hemostatic factors reflecting intrinsic thrombogenic and atherogenic potentials (tissue plasminogen activator [t-PA] antigen, plasminogen activator inhibitor-1, and factor VIII activity). We also evaluated the clinical applicability of these hemostatic factors by examining whether AF subjects with established clinical or echocardiographic predictors of thromboembolism had higher levels of these factors.</AbstractText>Of the 3,212 participants of a Chinese population-based study, 53 subjects (1.7%) with AF were identified. Among the hemostatic factors measured, t-PA antigen (median 12.8 vs 8.1 ng/mL; P < 0.01) and factor VIII activity (median 155% vs 133%; P < 0.05) were significantly higher in AF subjects after adjustment for age and sex. In multivariate analysis, features independently associated with t-PA antigen levels were AF, sex, body mass index, systolic blood pressure, total cholesterol, triglycerides, and left ventricular systolic dysfunction. Features independently associated with factor VIII activity levels included AF, age, and total cholesterol. Levels of both t-PA antigen and factor VIII activity were primarily elevated in AF subjects with predictors of thromboembolism (age > 75 years, hypertension, diabetes, and left ventricular systolic dysfunction), whereas in AF subjects with no thromboembolic predictors, plasma levels of hemostatic factors examined were similar to those without AF.</AbstractText>We demonstrated that nonvalvular AF was independently associated with increased peripheral levels of t-PA antigen and factor VIII activity. Levels of both hemostatic factors were primarily elevated in AF subjects with predictors of thromboembolism. Whether these hemostatic factors are independently predictive of future thromboembolic events in AF patients requires further investigation.</AbstractText> |
3,751 | [Processes of left atrial remodeling in myocardial infarction survivors as shown by esophageal rheography]. | To study the condition of the left atrium (LA) in patients with myocardial infarction (MI), 112 MI patients were compared to 24 healthy controls by the data obtained at ultrasonic investigation of the heart and esophageal rheography. 73.2% of the patients early after MI showed dilated LA. There were also changes in the ascending part of the rheographic atrial wave at its registration from the esophagus. Its marked prolongation (> 40% of the duration of the whole LA systole) is associated with alterations in the myocardial wall tonicity. If the above value was less, the number of supraventricular extrasystoles significantly increased, episodes of cardiac fibrillation occurred. Changed tonicity of the LA wall was accompanied also with prominent prolongation of the electrophysiological parameters of transesophageal pacing characterizing pacemaker's function and atrioventricular conduction. This suggests involvement not only left but also right atrium. Conclusion is that LA tonicity in MI is damaged and can be studied with esophageal rheography. |
3,752 | Dispersion of cell-to-cell uncoupling precedes low K+-induced ventricular fibrillation. | We hypothesize that hypokalemia-related electrolyte imbalance linked with abnormal elevation of intracellular free Ca2+ concentration can cause metabolic disturbances and subcellular alterations resulting in intercellular uncoupling, which favor the occurrence of malignant arrhythmias. Langendorff-perfused guinea pig heart (n = 44) was subjected to a standard Tyrode solution (2.8 mmol/l K+) followed by a K+-deficient solution (1.4 mmol/l K+). Bipolar ECG of the left atria and ventricle was continuously monitored and the incidence of ventricular fibrillation was evaluated. Myocardial tissue sampling was performed during stabilization, hypokalemia and at the onset of fibrillation. Enzyme activities of succinic dehydrogenase, glycogen phosphorylase and 5-nucleotidase were determined using in situ catalytic histochemistry. The main gap junction protein, connexin-43, was labeled using mouse monoclonal antibody and FITC conjugated goat antimouse antibody. Ultrastructure was examined by transmission electron microscopy. The free Ca2+ concentration was measured by the indo-1 method in ventricular cell cultures exposed to a K+-free medium. The results showed that sustained ventricular fibrillation appeared within 15-30 min of low K+ perfusion. This was preceded by ectopic activity, episodes of bigeminy and tachycardia. Hypokalemia induced moderate reversible and sporadically irreversible subcellular alterations of cardiomyocytes and impairment of intercellular junctions, which were heterogeneously distributed throughout myocardium. Patchy areas with decreased enzyme activities and diminished immunoreactivity of connexin-43 were found. Furthermore, lack of external K+ was accompanied by an increase of intracellular Ca2+. The prevention of Ca2+ overload by either 1 mmol/l Ni2+ (Na+/Ca2+ inhibitor), 2.5 micromol/l verapamil, 10 micromol/l d-sotalol or 10 micromol/l tedisamil was associated with the protection against fibrillation. The results indicate that hypokalemia induces Ca2+ overload injury and disturbances in intercellular coupling. Dispersion of these changes throughout the myocardium may serve as the basis for microreentry circuits and thus favor fibrillation occurrence. |
3,753 | Arrhythmogenic right ventricular cardiomyopathy: current diagnostic and management strategies. | Arrhythmogenic right ventricular cardiomyopathy (ARVC) is a heart muscle disease of unknown etiology characterized by the peculiar right ventricular (RV) involvement. Distinctive pathologic features are myocardial atrophy and fibro-fatty replacement of the RV free wall, and clinical presentation is usually related to ventricular tachycardias with a left bundle branch block pattern or ventricular fibrillation leading to cardiac arrest, mostly in young people and athletes. Later in the disease evolution, progression and extension of RV muscle disease and left ventricular involvement may result in right or biventricular heart failure. The diagnosis of ARVC may be difficult because of several problems with specificity of ECG abnormalities, different potential etiologies of ventricular arrhythmias with a left bundle branch morphology, assessment of RV structure and function, and interpretation of endomyocardial biopsy findings. Therefore, standardized diagnostic criteria have been proposed by the Study Group on ARVC of the European Society of Cardiology. According to these guidelines, the diagnosis of ARVC is based on the presence of major and minor criteria encompassing electrocardiographic, arrhythmic, morphofunctional, histopathologic, and genetic factors. Since the assessment of sudden death risk in patients with ARVC is still not well established, there are no precise guidelines to determine which patients need to be treated and what is the best management approach. The therapeutic options include beta-blockers, antiarrhythmic drugs, catheter ablation, and implantable cardioverter defibrillator (ICD). The ICD is the most effective safeguard against arrhythmic sudden death. However, its precise role in changing the natural history of ARVC by preventing sudden and nonsudden death needs to be evaluated by a prospective study of a large series of patients. In patients in whom ARVC has progressed to severe RV or biventricular systolic dysfunction with risk of thromboembolic complications, treatment consists of current therapy for heart failure including anticoagulant therapy. In cases of refractory congestive heart failure, patients may become candidates for heart transplantation. |
3,754 | Management of atrial flutter. | Atrial flutter is a macroreentrant arrhythmia that is associated with cardiovascular and pulmonary disease. In the United States, 200,000 new cases of atrial flutter can be expected to develop every year with a male to female ratio of over 2:1. This arrhythmia is associated with atrial fibrillation in over half the cases. It is also associated with an increased risk of thromboembolic complications, but less than that is seen with atrial fibrillation. The most common form of atrial flutter involves a large reentrant circuit within the right atrium, encircling the tricuspid annulus. Other, less common forms of atrial flutter may involve other anatomic barriers, atriotomy scars, and infarcted areas of the atria. Treatment of atrial flutter often involves electrical cardioversion and/or antiarrhythmic medications. Type I and Type III antiarrhythmic drugs are often used to terminate or prevent recurrent episodes and Type II (beta-blockers) and Type IV (calcium channel blockers) can be used to control the ventricular rate during atrial flutter. However, antiarrhythmic drugs alone control atrial flutter in only 50% to 60% of patients. Since the early 1990s, radiofrequency catheter ablation has been used to interrupt the reentrant circuit and prevent recurrences of atrial flutter. Radiofrequency ablation is acutely successful in over 90% of cases and avoids the long-term toxicity seen with antiarrhythmic drugs. Advanced mapping techniques and newer methods of delivering the radiofrequency lesions are being used to delineate unusual forms of atrial flutter and to minimize fluoroscopic exposure during the procedure. |
3,755 | [Effectiveness and safety of catheter ablation of the heart conduction tracts in tachyarrhythmia]. | An analysis of 490 operations of radiofrequency catheter destruction in 442 patients aged from 5 to 83 years has been made. 284 patients (64.3%) had congenital and "idiopathic" character of rhythm disturbances. The greater part of operations--459 (93.7%)--were performed on patients with supraventricular tachycardias, 31 operations (6.3%)--on patients with ventricular arrhythmias. Efficacy of operations on patients with congenital diseases of the conducting system of the heart was 94.8-100%, frequency of recurrences being 3.3-8%. Successful rhythm correction in 78% of patients with atrial flutter was due to the risk of appearance of recurrences and development of atrial fibrillation at late periods. Creation of atrio-ventricular blockade abolishes tachysystole in patients with ciliary arrhythmia, but life quality depends on the adequate system of stimulation. The frequency of complications after the catheter destruction is associated with the complex character of the intervention and increases when the manipulations are to be performed in the left chambers of the heart. |
3,756 | What is the optimal evaluation time of the QT dispersion after acute myocardial infarction for the risk stratification? | The sequential changes of the corrected QT dispersion (QTcD) were studied in 136 patients 1 day to 30 days after a transmural acute myocardial infarction (AMI) to investigate the optimal measurement time of QT dispersion for risk stratification. The study group included 136 patients (89 men; mean age, 57+/-10 years) with transmural AMI who were treated with thrombolytics (Tr+ group, n = 73) or not (Tr- group, n = 63) and 65 healthy controls (43 men; mean age, 56+/-7 years). Fourteen patients in whom ventricular tachycardia (VT), ventricular fibrillation (VF), or sudden cardiac death developed during the 30-day period were also evaluated as major cardiac arrhythmia (MCA) group. ECGs were obtained for each patient on days 1, 3, 5, 10, 15, and 30 after AMI. QTc dispersion in patients with AMI (for every period of QTcD after MI) was significantly more prolonged than in normal controls (49.3+/-16.3 ms) (p<0.001). QTcD was significantly greater in patients without thrombolytics than in patients with thrombolytics for every period (days 1, 3, 5, 10, 15, and 30) of QTcD after MI (p<0.001). The mean of QTcD was significantly greater in patients with MCA than in patients without MCA group for every period (days 1, 3, 5, 10, 15, and 30) of QTcD after MI (p < 0.05). Maximal QTcD was seen on day 10 (p < 0.05 1st vs day 10 for each group) after myocardial infarction, and then reached a plateau for an each group. The ideal time to measure the QTD for risk stratification is at least 10 days after AMI. |
3,757 | Prognostic factors of the results of cardiopulmonary resuscitation in a cardiology hospital. | To analyze the early and late results of cardiopulmonary resuscitation in a cardiology hospital and to try to detect prognostic determinants of both short- and long-term survival.</AbstractText>A series of 557 patients who suffered cardiorespiratory arrest (CRA) at the Dante Pazzanese Cardiology Institute over a period of 5 years was analyzed to examine factors predicting successful resuscitation and long-term survival.</AbstractText>Ressuscitation maneuvers were tried in 536 patients; 281 patients (52.4%) died immediately, and 164 patients (30.6%) survived for than 24 hours. The 87 patients who survived for more than 1 month after CRA were compared with nonsurvivors. Coronary disease, cardiomyopathy, and valvular disease had a better prognosis. Primary arrhythmia occurred in 73.5% of the >1-month survivor group and heart failure occurred in 12.6% of this group. In those patients in whom the initial mechanism of CRA was ventricular fibrillation, 33.3% survived for more than 1 month, but of those with ventricular asystole only 4.3% survived. None of the 10 patients with electromechanical dissociation survived. There was worse prognosis in patients included in the extreme age groups (zero to 10 years and 70 years or more). The best results occurred when the cardiac arrest took place in the catheterization laboratories. The worst results occurred in the intensive care unit and the hemodialysis room.</AbstractText>The results in our series may serve as a helpful guide to physicians with the difficult task of deciding when not to resuscitate or when to stop resuscitation efforts.</AbstractText> |
3,758 | Efficacy of pacing therapies for treating atrial tachyarrhythmias in patients with ventricular arrhythmias receiving a dual-chamber implantable cardioverter defibrillator. | Although overdrive pacing for treating atrial flutter is well established, the efficacy of device-based atrial pacing for treating spontaneous atrial tachyarrhythmias in patients with implantable cardioverter defibrillators (ICD) is unknown. This study evaluated the efficacy of novel pacing therapies for treating atrial tachyarrhythmias in patients receiving a dual-chamber ICD to treat ventricular tachyarrhythmias.</AbstractText>A Jewel AF ICD was implanted in 537 patients with ventricular arrhythmia who were followed for 11.4+/-8.2 months (74% had a documented history of atrial tachyarrhythmias). The device discriminated atrial tachycardia (AT) from atrial fibrillation (AF) on the basis of cycle length and regularity, and it used 3 different methods of overdrive atrial pacing (Ramp, Burst+, and 50-Hz burst) to treat AT episodes and one method (50-Hz burst) to treat AF episodes. Pacing successfully terminated 59% of 1500 spontaneous AT episodes in 127 patients and 30% of 880 AF episodes in 101 patients (P<0.001). With AT and AF episodes combined, pacing efficacy was 48%. Pacing efficacy was significantly reduced at AT cycle lengths </=220 ms and AF cycle lengths </=160 ms (P<0.01) The median time from pacing to AT/AF termination was 1.1 minute for the pacing successes and 96 minutes for the failures (P<0.001).</AbstractText>Atrial pacing terminated 48% of AT/AF episodes in patients with a history of ventricular arrhythmias. Pacing efficacy was greater for device-classified AT than AF. Pacing efficacy was significantly influenced by tachycardia cycle length. Successful pacing significantly reduces the time required for AT/AF termination.</AbstractText> |
3,759 | Inhibition of Na+/Ca2+ exchange by KB-R7943: transport mode selectivity and antiarrhythmic consequences. | The Na+/Ca2+ exchanger plays a prominent role in regulating intracellular Ca2+ levels in cardiac myocytes and can serve as both a Ca2+ influx and efflux pathway. A novel inhibitor, KB-R7943, has been reported to selectively inhibit the reverse mode (i.e., Ca2+ entry) of Na+/Ca2+ exchange transport, although many aspects of its inhibitory properties remain controversial. We evaluated the inhibitory effects of KB-R7943 on Na+/Ca2+ exchange currents using the giant excised patch-clamp technique. Membrane patches were obtained from Xenopus laevis oocytes expressing the cloned cardiac Na+/Ca2+ exchanger NCX1.1, and outward, inward, and combined inward-outward currents were studied. KB-R7943 preferentially inhibited outward (i.e., reverse) Na+/Ca2+ exchange currents. The inhibitory mechanism consists of direct effects on the transport machinery of the exchanger, with additional influences on ionic regulatory properties. Competitive interactions between KB-R7943 and the transported ions were not observed. The antiarrhythmic effects of KB-R7943 were then evaluated in an ischemia-reperfusion model of cardiac injury in Langendorff-perfused whole rabbit hearts using electrocardiography and measurements of left ventricular pressure. When 3 microM KB-R7943 was applied for 10 min before a 30-min global ischemic period, ventricular arrhythmias (tachycardia and fibrillation) associated with both ischemia and reperfusion were almost completely suppressed. The observed electrophysiological profile of KB-R7943 and its protective effects on ischemia-reperfusion-induced ventricular arrhythmias support the notion of a prominent role of Ca2+ entry via reverse Na+/Ca2+ exchange in this process. |
3,760 | The incidence of out-of-hospital ventricular fibrillation in Helsinki, Finland, from 1994 to 1999. | Early defibrillation by emergency medical services has been a success story in the treatment of ventricular fibrillation. This success has been followed by recommendations to allow public access to defibrillation equipment. We tracked the changes in incidence of ventricular fibrillation from prospectively collected data from the Helsinki Cardiac Arrest Register. We found that the incidence of out-of-hospital ventricular fibrillation of cardiac origin fell by 48% from 1994 to 1999 (p=0.0036). The primary and secondary prevention of coronary artery disease may not be the only reasons for this change and so new public-access defibrillation programmes should be delayed until our findings are confirmed. |
3,761 | Prevalence of left-ventricular systolic dysfunction and heart failure in the Echocardiographic Heart of England Screening study: a population based study. | Accurate data for prevalence rates for heart failure due to various causes, and for left-ventricular systolic dysfunction in all adults are unavailable. Our aim was to assess prevalence of left-ventricular systolic dysfunction and heart failure in a large representative adult population in England.</AbstractText>Of 6286 randomly selected patients aged 45 years and older, 3960 (63%) participated in the study. They came from 16 randomly selected general practices. We assessed patients by history and examination, electrocardiography, and echocardiography. Prevalence of left-ventricular systolic dysfunction (defined as ejection fraction <40%) and heart failure was calculated for the overall population on the basis of strict criteria and, when necessary, adjudication by a panel.</AbstractText>Left-ventricular systolic dysfunction was diagnosed in 72 (1.8% [95% CI 1.4-2.3]) participants, half of whom had no symptoms. Borderline left-ventricular function (ejection fraction 40-50%) was seen in 139 patients (3.5% [3.0-4.1]). Definite heart failure was seen in 92 (2.3%, [1.9-2.8]) and was associated with an ejection fraction of less than 40% in 38 (41%) patients, atrial fibrillation in 30 (33%), and valve disease in 24 (26%). Probable heart failure was seen in a further 32 (0.8% [0.6-1.1]) patients. In total, 124 (3.1% [2.6-3.7]) patients aged 45 years or older had definite or probable heart failure.</AbstractText>Heart failure is often misdiagnosed or underdiagnosed in primary care. Our results suggest that assessment of left-ventricular function in patients with suspected heart failure could lead to more effective diagnosis and treatment of this disorder.</AbstractText> |
3,762 | Atrial defibrillation thresholds of electrode configurations available to an atrioventricular defibrillator. | Little investigation has been conducted to assess the atrial defibrillation thresholds of electrode configurations using electrodes designed for internal ventricular defibrillation (right ventricle [RV], superior vena cava [SVC], and pulse generator housing [Can]) combined with coronary sinus (CS) electrodes. We hypothesized that a CS-->SVC+Can electrode configuration would have a lower atrial defibrillation threshold than a standard configuration for defibrillation, RV-->SVC+Can. We also tested the atrial defibrillation thresholds of five other configurations.</AbstractText>In 12 closed chest sheep, we situated a two-coil (RV, SVC) defibrillation catheter, a left-pectoral subcutaneous Can, and a CS lead. Atrial fibrillation was burst induced and maintained with continuous infusion of intrapericardial acetyl-beta-methylcholine chloride. Using fixed-tilt biphasic shocks, we determined the atrial defibrillation thresholds of seven test configurations in random order according to a multiple-reversal protocol. The peak voltage and delivered energy atrial defibrillation thresholds of CS-->SVC+Can (168+/-67 V, 2.68+/-2.40 J) were significantly lower than those of RV-->SVC+Can (215+/-88 V, 4.46+/-3.40 J). The atrial defibrillation thresholds of the other test configurations were RV+CS-->SVC+Can: 146+/-59 V, 1.92+/-1.45 J; RV-->CS+SVC+Can: 191+/-89 V, 3.53+/-3.19 J; CS-->SVC: 188+/-98 V, 3.77+/-4.14 J; SVC-->CS+ Can: 265+/-145 V, 7.37+/-9.12 J; and SVC-->Can: 516+/-209 V, 24.5+/-15.0 J.</AbstractText>The atrial defibrillation threshold of CS-->SVC+Can is significantly lower than that of RV-->SVC+Can. In addition, the low atrial defibrillation threshold of RV+CS-->SVC+Can merits further investigation. Based on corroboration of low atrial defibrillation thresholds of CS-based configurations in humans, physicians might consider using CS leads with atrioventricular defibrillators.</AbstractText> |
3,763 | Evaluation of left ventricular function and mitral regurgitation during left ventricular-based pacing in patients with heart failure. | Beneficial effects of left ventricular (LV)-based pacing on acute hemodynamic parameters were reported in several series, but only a few studies examined the long-term effects of this new pacing procedure.</AbstractText>To assess long-term effects of permanent LV-based pacing on LV function and mitral regurgitation (MR) in patients with refractory congestive heart failure (CHF).</AbstractText>A prospective evaluation of LV function and MR was performed in 23 patients with severe but stable CHF and left bundle branch block (mean QRS: 186+/-31 ms) by radionuclide and echocardiographic techniques at baseline and 6 months after implantation of a permanent LV-based (LV alone: 13 patients; biventricular: 10 patients) pacemaker programmed either in a DDD mode (sinus rhythm; n=14) or in a VVIR mode (atrial fibrillation; n=9).</AbstractText>Compared to baseline, the 6 months follow-up visit demonstrated a significant increase in radionuclide derived LV ejection fraction from 23.3+/-7 to 26.2+/-7% (P<0.01) and in echocardiographic LV fractional shortening from 13+/-4 to 16+/-6% (P<0.05), without any change in cardiac index, a significant decrease in LV end-diastolic diameter (from 73.2+/-6 to 71.2+/-7 mm; P<0.05), end-systolic diameter (from 63.6+/-6 to 60.2+/-8 mm; P<0.05) and color Doppler MR jet area (from 11.5+/-6 to 6.6+/-4 cm(1); P<0.001). A comparison of patients with LV pacing alone and patients with biventricular pacing showed similar beneficial effects of pacing on MR severity in the two subgroups and a non-significant trend for a better improvement of LV function during biventricular pacing.</AbstractText>Thus, in patients with severe CHF and left bundle branch block, permanent LV-based pacing may significantly improve LV systolic function and decrease MR.</AbstractText> |
3,764 | Beneficial effect of carvedilol on heart rate response to exercise in digitalised patients with heart failure in atrial fibrillation due to idiopathic dilated cardiomyopathy. | Fourteen digitalised patients diagnosed with heart failure (NYHA Functional class II) with idiopathic dilated cardiomyopathy in chronic established atrial fibrillation were administered carvedilol in addition to their anti-heart failure medications in an attempt to improve their heart rate control. Fourteen matched patients who did not receive carvedilol acted as control subjects. Patients treated with carvedilol showed significantly reduced resting heart rates (10-36%), maximal heart rates on exercise (5-20%) and an increased exercise time (2-30%) on treadmill stress tests (all P=0.001). Ventricular ectopic activity was also diminished. This was associated with symptomatic improvement in effort intolerance and palpitations. NYHA functional class, left ventricular dimensions and ejection fractions did not improve during the study period of 3 months. Thus, addition of carvedilol to digoxin had a beneficial effect on exercise tolerance in patients with idiopathic dilated cardiomyopathy in atrial fibrillation by virtue of an improved heart rate control both at rest and on exercise. Carvedilol was well tolerated despite impaired myocardial function. |
3,765 | [Cardiogenic ischemic strokes: pathogenetic aspects]. | Eighty-three patients with acute ischemic stroke (56 men and 27 women, mean age 90.1 +/- 10.8 years) were examined in order to elucidate the significance of paroxysmal heart rhythm disorders and silent myocardial ischemia and determine the pattern of hemorheological changes. Traditional clinical instrumental examinations were supplemented by Holter monitoring and measurements of a wide spectrum of hemostatic and hemorheological values. Cardiogenic ischemic strokes were pathogenetically heterogeneous. Holter monitoring helped detect the significance of paroxysmal atrial fibrillation in the pathogenesis of embolic cardiogenic stroke. One of the key factors in development of hemodynamic cardiogenic stroke was transitory bradyarrhythmia and deterioration of left-ventricular contractility. Cardiogenic strokes are associated with hemostatic activation with predominant changes in the plasma hemostasis, which dictates purposeful hemocorrection. |
3,766 | [Identification of patients with acute myocardial infarction that may be discharged early: prospective evaluation with simple clinical and instrumental indicators]. | The hospital stay for "uncomplicated" acute myocardial infarction (AMI) is often too long. A reduction in the length of hospitalization, if proven to be safe, is advantageous in terms of costs and health organization. Accordingly the aims of the present, prospective study, were to evaluate: 1) the patients with AMI eligible for early discharge; 2) the incidence of adverse cardiovascular events within 2 weeks of myocardial infarction; 3) the incidence of cardiovascular mortality at 6-month follow-up.</AbstractText>On the fifth day after AMI, 331 of 526 patients, consecutively admitted to our coronary care unit between March 1997 and August 1999, were assigned to "complicated" and "uncomplicated" AMI groups, according to clinical and non-invasive criteria. Uncomplicated myocardial infarction eligible for early discharge was defined in patients < 75 years, as the absence of a high risk personality, stroke, left bundle branch block, transient myocardial ischemia after the first 24 hours from AMI, clinical signs or echocardiographic evidence of left ventricular dysfunction (ejection fraction < 40%), ventricular fibrillation, sustained ventricular tachycardia, symptomatic bradyarrhythmias after the first 48 hours from AMI, cardioversion or defibrillation (after the first 48 hours) or the need for coronary angioplasty or coronary artery bypass grafting. Uncomplicated patients were discharged on the sixth day after AMI (hospital stay 6.5+/-0.72 days). A symptom-limited ergometric stress test was planned in the uncomplicated group 14 days after AMI. "Hard" (death, reinfarction) and "non-hard" (unstable angina, myocardial revascularization) adverse cardiovascular events were monitored at 2 weeks of follow-up, and cardiovascular mortality at 6-month follow-up.</AbstractText>Four (1.2%) hard (0.3% exitus and 0.9% reinfarction) and 7 (2.1%) non-hard adverse events occurred among patients with uncomplicated AMI at 2 weeks of follow-up. Patients with uncomplicated AMI who developed adverse events, presented during the primary coronary event creatine kinase (CK) and CK-MB serum levels which were significantly lower than those observed in patients who did not present adverse events. In the complicated group (hospital stay 9.9+/-1.79 days), from day 6 to 14 after AMI, 65 (33%) hard and non-hard events occurred. A significant reduction in mortality between the uncomplicated and complicated group (2.11 vs 27.17%, p < 0.0001) was observed at 6-month follow-up. Multivariate analysis showed a statistically significant difference for age and thrombolytic treatment.</AbstractText>This first Italian prospective study demonstrated the possibility of identifying, 5 days after AMI and on the basis of simple criteria and without a stress test, a low risk population of patients eligible for early discharge.</AbstractText> |
3,767 | [Complications in administration of contrast media in the catheterization laboratory: a 5-year retrospective study]. | Iodine contrast substances (CS) are used since the twenties of the 20th century. From the chemical aspect benzoic acid derivatives are involved which are classified according to their osmolality (high-low- and isoosmolar) tendency of ionization (ionic and non-ionic) and according to the molecular structure monomers and dimers). Side-effects are due to their osmotic, ionic and chemical action on tissues. They include a number of systemic and organ symptoms (cardiovascular, immunological, haemocoagulation, neurological and renal), from the clinical aspect divided into mild, medium severe and severe. The relatively high incidence of undesirable reactions when ionic high-molecular CS are used led to the-development of non-ionic preparations with a lower osmolality, the more extensive use of which is limited by economic factors. Moreover so far convincing clinical data are lacking that the higher incidence of undesirable reactions after the use of CS has a clinical impact.</AbstractText>To summarize experience with administration of CS in the catheterization laboratory of the Cardiocentre of the General Faculty Hospital during diagnostic and intervention procedures within 5 years with regard to the occurrence of undesirable effects when comparing ionic and non-ionic CS.</AbstractText>Retrospective analysis of a group of patients examined in the catheterization laboratory to whom a CS was administered during the period between Jan. 1 1995 and Dec. 31 1999.</AbstractText>In 1995-1999 (5 years) in the catheterization laboratory a total of 10,149 procedures where implemented where ionic (ioxitalam-Telebrix 350) and non-ionic (iopromide Ultravist 370, ioversol--Optiray 370 and iomeprol-Iomeron 350) contrast substances were administered. Ionic CS were administered in 4,668 (46%) and non-ionic CS in 5,481 (54%) instances. Undesirable effects were recorded in a total of 107 (1.1%) patients, incl. ventricular fibrillation in 76 (0.75%), cardiac arrest in 12 (0.12%) and in 19 (0.19%) there were other undesirable effects (weakness, nausea, hypotension, flush, urtica etc.). Ionic and non-ionic CS participated equally in complications: ionic CS in 53 (49.5%) cases and non-ionic CS in 54 (50.5%), whereby no difference was observed in the type of complications. No death in conjucntion with administration of CS was observed.</AbstractText>The use of contemporary contrast substances in the catheterization laboratory for diagnostic and intervention procedures on the heart is relatively safe with a minimal risk of development of serious complications. No difference was observed between the use of ionic and non-ionic CS.</AbstractText> |
3,768 | Comparison of epinephrine with vasopressin on bone marrow blood flow in an animal model of hypovolemic shock and subsequent cardiac arrest. | The intraosseous route is an emergency alternative for the administration of drugs and fluids if vascular access cannot be established. However, in hemorrhagic shock or after vasopressors are given during resuscitation, bone marrow blood flow may be decreased, thus impairing absorption of intraosseously administered drugs. In this study, we evaluated the effects of vasopressin vs. high-dose epinephrine in hemorrhagic shock and cardiac arrest on bone marrow blood flow.</AbstractText>Prospective, randomized laboratory investigation that used an established porcine model for measurement of hemodynamic variables and organ blood flow.</AbstractText>University hospital laboratory.</AbstractText>Fourteen pigs weighing 30 +/- 3 kg.</AbstractText>Radiolabeled microspheres were injected to measure bone marrow blood flow during a prearrest control period and during hypovolemic shock produced by rapid hemorrhage of 35% of the estimated blood volume. In the second part of the study, ventricular fibrillation was induced; after 4 mins of untreated cardiac arrest and 4 mins of standard cardiopulmonary resuscitation, a bolus dose of either 200 microg/kg epinephrine (n = 6) or 0.8 units/kg vasopressin (n = 6) was administered. Defibrillation was attempted 2.5 mins after drug administration, and blood flow was assessed again at 5 and 30 mins after successful resuscitation.</AbstractText>Mean +/- sem bone marrow blood flow decreased significantly during induction of hemorrhagic shock from 14.4 +/- 4.1 to 3.7 +/- 1.8 mL.100 g-1.min-1 in the vasopressin group and from 18.2 +/- 4.0 to 5.2 +/- 1.0 mL.100 g-1.min-1 in the epinephrine group (p =.025 in both groups). Five minutes after return of spontaneous circulation, mean +/- sem bone marrow blood flow was 3.4 +/- 1.1 mL.100 g-1.min-1 after vasopressin and 0.1 +/- 0.03 mL.100 g-1.min-1 after epinephrine (p =.004 for vasopressin vs. epinephrine). At the same time, bone vascular resistance was significantly (p =.004) higher in the epinephrine group when compared with vasopressin (1455 +/- 392 vs. 43 +/- 19 mm Hg. mL-1.100 g.min, respectively).</AbstractText>Bone blood flow responds actively to both the physiologic stress response of hemorrhagic shock and vasopressors given during resuscitation after hypovolemic cardiac arrest. In this regard, bone marrow blood flow after successful resuscitation was nearly absent after high-dose epinephrine but was maintained after high-dose vasopressin. These findings emphasize the need for pressurized intraosseous infusion techniques, because bone marrow blood flow may not be predictable during hemorrhagic shock and drug therapy.</AbstractText> |
3,769 | Severe cardiac arrhythmia on fexofenadine? | (1) One case of ventricular fibrillation during fexofenadine administration has been reported in a man with a pre-existing long QT interval. |
3,770 | Shock reduction using antitachycardia pacing for spontaneous rapid ventricular tachycardia in patients with coronary artery disease. | Implantable cardioverter-defibrillators (ICDs) can terminate some ventricular tachycardias (VTs) painlessly with antitachycardia pacing (ATP). ATP has not routinely been applied for VT >188 bpm because of concerns about efficacy, risk of acceleration, and delay of definitive shock therapy. This prospective, multicenter study evaluated the efficacy of empirical ATP to terminate fast VT (FVT; >188 bpm).</AbstractText>Two hundred twenty coronary artery disease patients received ICDs for standard indications. Empirical, standardized therapy was programmed so that all FVT episodes (average cycle length [CL] 240 to 320 ms, 250 to 188 bpm) were treated with 2 ATP sequences (8-pulse burst pacing train at 88% of the FVT CL) before shock delivery. A total of 1100 episodes of spontaneous ventricular tachyarrhythmias occurred during a mean of 6.9+/-3.6 months of follow-up. Fifty-seven percent were classified as slow VT (CL>/=320 ms), 40% as FVT (240 ms</=CL<320 ms), and 3% as ventricular fibrillation (CL<240 ms). A total of 446 FVT episodes, mean CL=301+/-24 ms, occurred in 52 patients (median 2 episodes per patient). ATP terminated 396 FVT episodes (89%), with an adjusted efficacy of 77% (95% CI 68% to 83%). VT acceleration caused by ATP occurred in 10 FVT episodes (4%). FVT arrhythmic syncope occurred on 9 occasions (2%) in 4 patients.</AbstractText>FVT (CL<320 ms) is common in ICD patients. ATP can terminate 3 of 4 of these episodes with a low incidence of acceleration and syncope. ATP for FVT may safely reduce the morbidity of painful shocks.</AbstractText> |
3,771 | Phased chest and abdominal compression-decompression versus conventional cardiopulmonary resuscitation in out-of-hospital cardiac arrest. | Several methods have been developed to improve the efficacy of mechanical resuscitation, because organ perfusion achieved with conventional manual resuscitation is often insufficient. In animal studies, phased chest and abdominal compression-decompression resuscitation by use of the Lifestick device has resulted in a better outcome compared with that of conventional resuscitation. In end-of-life patients, an increased coronary perfusion pressure was achieved. The aim of the present study was to determine the feasibility, safety, and efficacy of the Lifestick compared with conventional resuscitation in patients with sudden nontraumatic out-of-hospital cardiac arrest.</AbstractText>The crews of 4 mobile intensive care units, staffed by an emergency physician and a paramedic, were trained to use the device. Fifty patients were randomized by sealed envelopes to either Lifestick (n=24) or conventional (n=26) resuscitation. No differences were found regarding demographic and logistical conditions between the groups. Nineteen of the patients (73%) with conventional resuscitation had ventricular fibrillation, 13 of whom survived to hospital admission (no survivals with other arrhythmias) and 7 were discharged. In contrast, in the Lifestick-CPR group, only 9 patients had ventricular fibrillation (38%; P=<0.02; OR, 2.5; 95% CI, 0.6 to 10.6). Four of these 9 patients and 5 of 15 patients with other arrhythmias survived to hospital admission, but none survived to hospital discharge. Autopsy in a subgroup of patients who died at the scene revealed less injuries with Lifestick than with conventional resuscitation.</AbstractText>Lifestick resuscitation is feasible and safe and may be advantageous in patients with asystole or pulseless electric activity.</AbstractText> |
3,772 | Isolated non-compaction of the left ventricle: a rare indication for transplantation. | This report describes the diagnostic difficulty encountered in a young female patient presenting with neurologic symptoms, atrial fibrillation and severe left ventricular systolic dysfunction, eventually leading to cardiac transplantation. The scrutiny used in the evaluation of the particular aspect of the left ventricle, and the integration of the information obtained from echocardiography, angiography and magnetic resonance imaging, led to the diagnosis of a rare and mostly unknown cause of cardiac failure. The correct identification of this entity is mandatory because enhanced risk of thromboembolism and malignant arrhythmia should be anticipated. A review of the literature revealed only 6 patients in whom isolated non-compaction of the left ventricle was treated by heart transplantation. |
3,773 | Characterization of post-discharge atrial fibrillation following open-heart surgery in uncomplicated patients referred to an early rehabilitation program. | Atrial fibrillation (AF) is frequently observed after open-heart surgery, following discharge from the cardiac surgery clinic. Compared to those usually reported in the early postoperative period, this arrhythmia is delayed in onset and is often a cause of re-hospitalization. Post-discharge AF has never been characterized in the literature.</AbstractText>We retrospectively analyzed post-discharge AF occurring within 30 days of coronary artery bypass graft or of valvular procedures in 376 patients referred to an early postoperative rehabilitation program. To investigate the probability of the persistence of post-discharge AF, we prospectively examined 232 patients who had undergone valvular procedures.</AbstractText>An arrhythmia was recognized in 61/376 patients (16%), resulted in worsening of the NYHA functional class in 27 (44%) and in life-threatening hemodynamic effects requiring urgent cardioversion in 5 (8%). Events were predicted by the occurrence of postoperative AF (6-fold higher risk), left ventricular hypertrophy, an enlarged left atrium and valvular pathology (3-fold) and by the lack of beta-blocker protection (5-fold). AF persisted in 20/232 (9% of the study population, 18% of patients who had post-discharge AF) and had a relevant impact on the patient's clinical status. Predictors of events were older age, an enlarged left atrium and a lower left ventricular ejection fraction.</AbstractText>Post-discharge AF following open-heart surgery is frequent in patients undergoing valvular procedures and often persists over time. The clinical impact of the arrhythmia is relevant, it might cause re-hospitalizations in many circumstances and, consequently, may have an impact on hospital resources. Events are much less frequent in patients taking beta-blockers than in those who do not, and they can be predicted by simple variables observed in the early stages after surgery.</AbstractText> |
3,774 | Plasma CPU-86017 concentrations regarding suppression of ouabain-induced cardiac arrhythmias and decrease of heart rate in guinea pigs. | To determine the effective plasma levels of CPU-86017 which could suppress the cardiac arrhythmias induced by i.v. ouabain in guinea pigs.</AbstractText>The cardiac arrhythmias and the heart rate were monitored by ECG traces. Blood samples were collected to determine plasma levels using HPLC assay. TXB2 and 6-keto-PGF1 alpha were measured in plasma.</AbstractText>The plasma concentrations of CPU-86017 which were effective to suppress ventricular fibrillation (VF) and heart rate were 0.13-0.23 mg/L and 0.13-0.31 mg/L, respectively. A reduction of TXB2 levels and an elevation of 6-keto-PGF1 alpha levels were observed after CPU-86017 i.v. administration.</AbstractText>The arrhythmia-suppressing and heart rate-slowing effect of CPU-86017 followed a linear relationship with its concentrations in plasma.</AbstractText> |
3,775 | Characterization of the 16 blanking periods of the Medtronic GEM DR dual chamber defibrillators. | We determined the blanking periods of the Medtronic GEM DR dual chamber defibrillators by using a simulator to deliver signals mimicking arrhythmias into external devices programmed to various settings. The blanking periods for the tachycardia and bradycardia functions were measured in the atrial and ventricular channels after a paced atrial event, sensed atrial event, paced ventricular event and sensed ventricular event, adding to a total of 16 blanking periods. Our findings complement the incomplete or unclear specifications published by the manufacturer. Accurate knowledge of blanking periods is essential for the interpretation of device function. |
3,776 | Merits and limitations of the mode switching rate stabilization pacing algorithms in the implantable cardioverter defibrillator. | The 7250 Jewel AF Medtronic model of ICD is the first implantable device in which both therapies for atrial arrhythmias and pacing algorithms for atrial arrhythmia prevention are available. Feasibility of that extensive atrial arrhythmia management requires correct and synergic functioning of different algorithms to control arrhythmias.</AbstractText>The ability of the new pacing algorithms to stabilize the atrial rate following termination of treated atrial arrhythmias was evaluated in the marker channel registration of 600 spontaneously occurring episodes in 15 patients with the Jewel AF. All patients (55+/-15 years) had structural heart disease and documented atrial and ventricular arrhythmias. Dual chamber rate stabilization pacing was present in 245 (41 %) of episodes following arrhythmia termination and was a part of the mode switching operation during which pacing was provided in the dynamic DDI mode. This algorithm could function as the atrial rate stabilization pacing only when there was a slow spontaneous atrial rhythm or in presence of atrial premature beats conducted to the ventricles with a normal AV time. In case of atrial premature beats with delayed or absent conduction to the ventricles and in case of ventricular premature beats, the algorithm stabilized the ventricular rate. The rate stabilization pacing in DDI mode during sinus rhythm following atrial arrhythmia termination was often extended in time due to the device-based definition of arrhythmia termination. This was also the case in patients, in whom the DDD mode with true atrial rate stabilization algorithm was programmed.</AbstractText>The rate stabilization algorithms in the Jewel AF applied after atrial arrhythmia termination provide pacing that is not based on the timing of atrial events. Only under certain circumstances the algorithm can function as atrial rate stabilization pacing. Adjustments in availability and functioning of the rate stabilization algorithms might be of benefit for the clinical performance of pacing as part of device therapy for atrial arrhythmias.</AbstractText> |
3,777 | Interactions between pacing and arrhythmia detection algorithms in the dual chamber implantable cardioverter defibrillator. | Dual chamber implantable cardioverter defibrillator (ICD) combines the possibility to detect and treat ventricular and atrial arrhythmias with the possibility of modern heart stimulation techniques. Advanced pacing algorithms together with extended arrhythmia detection capabilities can give rise to new types of device-device interactions. Some of the possible interactions are illustrated by four cases documented in four models of dual chamber ICDs. Functioning of new features in dual chamber devices is influenced by the fact that the pacemaker is not a separate device but a part of the ICD system and that both are being used in a patient with arrhythmia. Programming measures are suggested to optimize use of new pacing algorithms while maintaining correct arrhythmia detection. |
3,778 | Atrial fibrillation: a risk factor for increased mortality--an AVID registry analysis. | Emerging evidence suggests that atrial fibrillation is not a benign arrhythmia. It is associated with increased risk of death. The magnitude of association is controversial and potential causes remain unknown. Patients in the registry of the Antiarrhythmics Versus Implantable Defibrillators (AVID) Trial form the basis for this report. Baseline variables, in particular the presence or absence of a history of atrial fibrillation/flutter, were examined in relation to survival. Multivariate Cox regression was used to adjust for differences in important baseline co-variables using 27 pre-selected variables. There were 3762 subjects who were followed for an average of 773+/-420 days; 1459 (39 %) qualified with ventricular fibrillation and 2303 (61 %) with ventricular tachycardia. A history of atrial fibrillation/flutter was present in 24.4 percent. There were many differences in baseline variables between those with and those without a history of atrial fibrillation/flutter. After adjustment for baseline differences, a history of atrial fibrillation/flutter remained a significant independent predictor of mortality, (relative risk=1.20; 95 % confidence intervals=1.03-1.40; p=0.020). Antiarrhythmic drug use, other than amiodarone or sotalol, was also a significant independent predictor of mortality (relative risk 1.34; 95 % confidence intervals 1.07-1.69, p=0.011. Atrial fibrillation/flutter is a significant independent risk factor for increased mortality in patients presenting with ventricular tachyarrhythmias. This risk may have been overestimated in previous studies that could not adjust for the proarrhythmic effects of antiarrhythmic drugs other than amiodarone or sotalol. |
3,779 | Significance of inducible ventricular fibrillation in patients with coronary artery disease and unexplained syncope. | This study was designed to determine the incidence and prognostic significance of inducible ventricular fibrillation (VF) in patients with coronary artery disease (CAD) and unexplained syncope.</AbstractText>Current American College of Cardiology/American Heart Association practice guidelines recommend implantation of internal cardioverter-defibrillators (ICDs) in patients with unexplained syncope in whom either ventricular tachycardia (VT) or VF is inducible during electrophysiologic (EP) testing. Although the prognostic significance of inducible monomorphic VT is known, the significance of inducible VF remains undefined.</AbstractText>We evaluated 118 consecutive patients with CAD and unexplained syncope who underwent EP testing. Sustained monomorphic VT was inducible in 53 (45%) patients; in 20 (17%) patients, VF was the only inducible arrhythmia; and no sustained ventricular arrhythmia was inducible in the remaining 45 (38%) patients. The latter two groups of 65 (55%) patients make up the study population.</AbstractText>There were 16 deaths among the study population during a follow-up period of 25.3 +/- 19.6 months. The overall one- and two-year survival in these patients was 89% and 81%, respectively. No significant difference in survival was observed between patients with and without inducible VF (80% power to detect a fourfold survival difference).</AbstractText>In 17% of patients with CAD and unexplained syncope, VF is the only inducible ventricular arrhythmia. Within the limits of this pilot study, long-term follow-up of patients with and without inducible VF demonstrates no difference in survival between the two groups. Therefore, the practice of ICD implantation in patients with CAD, unexplained syncope and inducible VF, especially with triple ventricular extrastimuli, may merit reconsideration.</AbstractText> |
3,780 | Results of surgical repair of ostium primum atrial septal defect in adult patients. | Ostium primum atrial septal defect (ASD I) is very rarely observed in the adults. Although ASD I was first corrected surgically almost 50 years ago, the efficacy of surgical treatment in adults has not been well documented. Thus, the long-term outcome of patients aged over 20 years and having surgical repair of ASD I was examined.</AbstractText>Fifteen patients (10 males, five females; mean age 31.4+/-13.1 years; range: 20 to 56 years) who had surgical repair of ASD I between 1982 and 2000 were followed. All patients were examined physically and underwent chest radiography, ECG and echocardiography (cross-sectional and Doppler) before and after surgery. Autologous pericardium was used to close the defect in 14 patients, and a direct suture was used in one patient. Mitral valvuloplasty (repair of the cleft) was performed in 12 patients, and De Vega annuloplasty in eight.</AbstractText>There were no hospital deaths. In one case a pacemaker was implanted five days after surgery because of complete heart block. Preoperatively, nine patients (60%) were in NYHA classes III and IV; at the end of follow up, 14 (93.3%) were in classes I and II. Preoperatively, 13 patients had sinus rhythm, and one each had atrial fibrillation (AF) and rhythm from the atrioventricular sinus. During follow up, three patients developed AF which was treated successfully with electrical cardioversion. The preoperative mean cardiac volume index of 695 +/- 216 ml/m(2) was reduced significantly after repair to 523 +/- 108 ml/m(2) (p < 0.05). Before surgery, mitral regurgitation was observed (severe in five cases, moderate in seven, mild in three). Postoperatively, a residual intracardiac shunt was identified in one case. Postoperative mitral regurgitation was noted in six patients (moderate in two, mild in four). The right ventricular dimension was decreased significantly, from 5.0 +/- 1.5 mm before surgery to 3.2 +/- 0.6 mm after repair (p < 0.001).</AbstractText>Patients aged over 20 years with ASD I benefit from surgical repair of the defect.</AbstractText> |
3,781 | Atrial activity enhancement by Wiener filtering using an artificial neural network. | This paper describes a novel technique for the cancellation of the ventricular activity for applications such as P-wave or atrial fibrillation detection. The procedure was thoroughly tested and compared with a previously published method, using quantitative measures of performance. The novel approach estimates, by means of a dynamic time delay neural network (TDNN), a time-varying, nonlinear transfer function between two ECG leads. Best results were obtained using an Elman TDNN with nine input samples and 20 neurons, employing a sigmoidal tangencial activation in the hidden layer and one linear neuron in the output stage. The method does not require a previous stage of QRS detection. The technique was quantitatively evaluated using the MIT-BIH arrhythmia database and compared with an adaptive cancellation scheme proposed in the literature. Results show the advantages of the proposed approach, and its robustness during noisy episodes and QRS morphology variations. |
3,782 | A malignant phenotype of hypertrophic cardiomyopathy caused by Arg719Gln cardiac beta-myosin heavy-chain mutation in a Chinese family. | Mutations of the cardiac beta-myosin heavy-chain (beta-MHC) gene cause hypertrophic cardiomyopathy (HCM). Recent genotype-phenotype correlation studies have shown that mutations carry prognostic significance. We studied five unrelated Chinese families with hypertrophic cardiomyopathy. Exons 3-27 and 40 of the beta-MHC gene were screened with both the polymerase chain reaction-single-strand conformation polymorphism (PCR-SSCP) method and the cycle sequencing of the PCR products. A previously reported heterozygous mutation Arg719Gln (arginine-->glutamine in codon 719) in exon 19 was found in one family. The proband is a 30-year-old female diagnosed at age of 25 years when she presented with symptoms of chest pain, palpitations, and frequent incidents of dizziness and syncope. A two-dimensional echocardiogram showed moderate asymmetrical septal hypertrophy with left atrial enlargement. There was no obstruction of the left ventricular outflow tract (LVOT). The patient also developed atrial fibrillation. The proband's mother and one of her sisters had similar clinical manifestations and both died suddenly at the age of 38 years. In addition, two silent nucleotide substitutions (ACT63ACC, TTT244TTC) in the cardiac beta-MHC gene were identified in the other four families. These synonymous mutations did not cosegregate with the disease in the families and they were also present in the 60 healthy and age-matched control subjects. Of the five families studied, we did not find any missense mutation in the remaining four families. The missense mutation Arg719Gln found in the Chinese family is associated with a malignant phenotype of severe clinical symptoms and poor survival prognosis. This mutation also causes atrial enlargement and atrial fibrillation. Our study provides further evidence that the mutation, which alters the charge of the myosin heavy chain, is associated with a serious clinical outcome. |
3,783 | [Effect of percutaneous transvenous mitral commissurotomy for the preservation of sinus rhythm in patients with mitral stenosis]. | Atrial fibrillation is frequently associated with mitral stenosis and is considered to be an unfavorable factor for the long-term prognosis. The efficacy of percutaneous transvenous mitral commissurotomy(PTMC) was examined for the preservation of sinus rhythm in patients with mitral stenosis after PTMC.</AbstractText>Long-term clinical data after PTMC were obtained from 71 patients who had undergone PTMC from March 1989 to September 1999. Eighteen patients in sinus rhythm before PTMC were divided into two groups: the SR group(n = 5) who remained in sinus rhythm, and the Af group(n = 13) who showed change from sinus rhythm to persistent or paroxysmal atrial fibrillation after PTMC.</AbstractText>Age, sex, mitral valve area(1.4 +/- 0.3 vs 1.2 +/- 0.3 cm2), mean mitral pressure gradient(14.3 +/- 5.5 vs 12.6 +/- 5.9 mmHg), mean left atrial pressure(15.9 +/- 7.6 vs 19.0 +/- 7.7 mmHg), left ventricular end-diastolic pressure(7.5 +/- 2.8 vs 9.3 +/- 3.9 mmHg), left ventricular end-diastolic volume index(77 +/- 13 vs 82 +/- 14 ml/m2), left ventricular ejection fraction(60 +/- 6% vs 55 +/- 4%) and cardiac output(5.1 +/- 0.4 vs 4.9 +/- 0.8 l/m2) before PTMC were not different between the two groups. Changes in mean mitral pressure gradient, mean left atrial pressure and cardiac output immediately after PTMC were not different statistically. Mitral valve area immediately after PTMC was significantly greater in the SR group compared to the Af group(2.3 +/- 0.3 vs 1.8 +/- 0.3 cm2, p < 0.05). The change in mitral valve area was also greater in the SR group(1.0 +/- 0.2 vs 0.6 +/- 0.4 cm2, p < 0.05), but there was no statistical difference in the percentage change of mitral valve area between before and immediately after PTMC(SR group 78 +/- 35% vs Af group 50 +/- 35%). End-diastolic pressure, end-diastolic volume index and ejection fraction immediately after PTMC were not statistically different.</AbstractText>The final mitral valve area immediately after PTMC in the patients with mitral stenosis in sinus rhythm, but not the changes of mean mitral pressure gradient, mean left atrial pressure or cardiac output, is important for the maintenance of sinus rhythm.</AbstractText> |
3,784 | Echocardiographic evaluation of right ventricular systolic functions in pure mitral stenosis. | Detailed echocardiographic evaluation of right ventricular muscle thickness and systolic functions was performed in twenty two cases of isolated rheumatic mitral stenosis without clinical signs of systemic venous congestion, tricuspid regurgitation or atrial fibrillation. Twenty two age and sex matched normal persons formed the control group. Right ventricular thickness was significantly increased in the patients with mitral stenosis. End-diastolic and end-systolic long axis measurements and areas were significantly increased and fractional shortening of these parameters was significantly reduced in the patient group. Our results show that right ventricular systolic functions are significantly impaired even in absence of clinical signs of systemic venous congestion. This impairment of systolic function did not correlate with pulmonary flow acceleration time. Myocardial involvement in rheumatic process could be one possibility. Systolic movement of the Tricuspid annulus and right ventricular mid cavity short axis dimension were not sensitive in detecting right ventricular systolic dysfunction. |
3,785 | [Implantable cardioverter-defibrillators in the prevention of sudden cardiac death]. | The aim of this work is to characterize and analyse the spectrum of therapies delivered from implantable cardioverter-defibrillators (ICD), to evaluate their effectivity and to mark the most effective types of antitachycardia stimulations (ATP), cardioversion (CV) and defibrillation (CD). To compare our results with references and give precautions of trouble-shootings. Our patients had implanted ICDs according to standard criteria for ICD implantations. Before discharge from hospital we performed predischarge test of their ICD. Than we followed them periodically each three months. We have observed 72 ICD pts (55 M, 17 F) in the mean age of 62.7 +/- 12.2 years the with mean LVEF was 0.37 +/- 0.11. The mean follow-up was 21 +/- 12.8 months. Each examination was managed through anamnesis of symptoms accompanying the beginning of arrhythmia, the sensation of ICD therapy by patient, followed by interrogation of the ICD memory. All obtained episodes were analysed. During the follow-up 1023 episodes of malignant ventricular arrhythmias were detected and effectively terminated. 7 pts died. During the therapy the ATP reached 83% in comparison with CV, CD which reached only 17%. The dominating symptoms were palpitations and presyncopes. In comparison with initial arrhythmias leading to implantations of ICDs (ventricular fibrillations for most of the cases--54%) the significantly higher number of spontaneous episodes were caused by monomorphic ventricular tachycardias VT (92.0%). We had no sudden cardiac death in our pts. In the indicated pts with a high risk of sudden arrhythmic death, the ICD therapy is characterized as very effective and is associated with high safety, low discomfort and when up to date algorithms for detection being used, then only adequate part of the inappropriate therapies occurs (10% patients, 3.2% from the number of episodes). The therapy by implantable cardioverter-defibrillators has had an important role in treating pts with life-threatening ventricular arrhythmias. |
3,786 | [Heart failure in hypertensive patients with left ventricular hypertrophy]. | Left ventricular hypertrophy (LVH) is supposed to be a useful marker of cardiovascular complications during the course of hypertension. Authors compared the presence of heart failure, left ventricular diastolic dysfunction and chronic atrial fibrillation in hypertensive patients with and without left ventricular hypertrophy defined by echocardiography. Hospital records of 192 hypertensives treated in our medical department during years 1996-1999 were analysed. Left ventricular hypertrophy was defined by echocardiography (Penn convention) as left ventricular mass index > 134 g/m2 in men and > 110 g/m2 in women. Presence of LVH was found in 128 patients (mean age 65.9 years), absence of LVH in 64 patients (mean age 64.8 years). Both groups of hypertensives were matched by demographic parameters, by the presence of hyperlipidemia, by smoking habits. Hypertensive patients with left ventricular hypertrophy were more often treated by ACE inhibitors. There were statistically significant more patients with heart failure, left ventricular diastolic dysfunction and chronic atrial fibrillation in LVH-positive patients than in LVH-negative once. There was also statistically significant lower ejection fraction (50.3 +/- 11.4% vs 56.5 +/- 7.4%) in LVH-positive patients than in LVH-negative once. Left ventricular hypertrophy in patients with hypertension brings usually a complicated course of the disease with a high contribution to the development of chronic heart failure. |
3,787 | Ventricular fibrillation during off-pump coronary artery bypass grafting: transcranial Doppler and clinical findings. | A 73-year-old male developed ventricular fibrillation which lasted for 2 min and 24 s, during off-pump coronary artery bypass grafting. Cerebral hemodynamics were assessed by continuous transcranial Doppler monitoring. Ventricular fibrillation resulted in an immediate fall in cerebral blood flow velocities to almost zero with only slight fluctuations. This was then followed by a pronounced reactive hyperperfusion. Cerebral magnetic resonance imaging examinations and detailed neurological and neuropsychological evaluations were performed before and at 3 and 12 months after surgery. No evidence of cerebral damage was found. |
3,788 | Electrical induction of ventricular fibrillation for resuscitation from postcountershock pulseless and asystolic cardiac arrests. | There is increasing evidence that defibrillation from prolonged ventricular fibrillation (VF) before CPR decreases survival. It remains unclear, however, whether harmful effects are due primarily to initial countershock of ischemic myocardium or to resultant postdefibrillation rhythms (ie, pulseless electrical activity [PEA] or asystole).</AbstractText>We induced 15 dogs into 12 minutes of VF and randomized them to 3 groups. Group 1 was defibrillated at 12 minutes and then administered advanced cardiac life support (ACLS); group 2 was allowed to remain in VF and was subsequently defibrillated after 4 minutes of ACLS; group 3 was defibrillated at 12 minutes, electrically refibrillated, and then defibrillated after 4 minutes of ACLS. All group 1 and 3 animals were defibrillated into PEA/asystole at 12 minutes. After 4 minutes of ACLS, group 2 and 3 animals were effectively defibrillated into sinus rhythm. The extension of VF in group 2 and 3 subjects paradoxically resulted in shorter mean resuscitation times (251+/-15 and 245+/-7 seconds, respectively, versus 459+/-66 seconds for group 1; P<0.05) and improved 1-hour survival (10 of 10 group 2 and 3 dogs versus 1 of 5 group 1 dogs; Fisher's exact, P<0.005) compared with more conservatively managed group 1 subjects.</AbstractText>Precountershock CPR during VF appears more conducive to resuscitation than CPR during postcountershock PEA or asystole. The intentional induction of VF may prove useful in the management of PEA and asystolic arrests.</AbstractText> |
3,789 | Cardioprotective effect afforded by transient exposure to phosphodiesterase III inhibitors: the role of protein kinase A and p38 mitogen-activated protein kinase. | Phosphodiesterase III inhibitors (PDEIII-Is) improve the hemodynamic status of heart failure via inotropic/vasodilatory effects attributable to the increase in intracellular cAMP level. Direct cardioprotection by PDEIII-Is and its underlying mechanisms, however, have not been identified. We tested the infarct size-limiting effect of PDEIII-Is and the roles of cAMP, protein kinase (PK) A, PKC, and mitogen-activated protein kinase (MAPK) families in open-chest dogs. Methods and Results-- Milrinone, olprinone (PDEIII-Is), or dibutyryl-cAMP (db-cAMP) was injected intravenously 30 minutes before 90-minute ischemia, followed by 6 hours of reperfusion. Olprinone was also examined with an intracoronary cotreatment with a PKA inhibitor (H89), a PKC inhibitor (GF109203X), an extracellular signal-regulated kinase kinase (MEK) inhibitor (PD98059), or a p38 MAPK inhibitor (SB203580) throughout the preischemic period. Either PDEIII-Is or db-cAMP caused substantial hemodynamic changes, which returned to control levels in 30 minutes. Collateral flow and percent risk area were identical for all groups. Both PDEIII-Is and db-cAMP increased myocardial p38 MAPK activity during the preischemic period, which was blocked by H89, but not by GF109203X. Both PDEIII-Is and db-cAMP reduced infarct size (19.1+/-4.1%, 17.5+/-3.3%, and 20.3+/-4.8%, respectively, versus 36.1+/-6.2% control, P<0.05 each). Furthermore, the effect of olprinone was blunted by either H89 (35.5+/-6.4%) or SB203580 (32.6+/-5.9%), but not by GF109203X or PD98059. H89, GF109203X, PD98059, or SB203580 alone did not influence infarct size.</AbstractText>Pretreatment with PDEIII-Is has cardioprotective effects via cAMP-, PKA-, and p38 MAPK-dependent but PKC-independent mechanisms in canine hearts.</AbstractText> |
3,790 | [Circular hemorrhagic subendocardial necrosis after heart arrest and resuscitation]. | A 19 year old boy, previously healthy suffered a cardiac arrest by getting up. Ten minutes afterwards the general practitioner commenced cardiopulmonary resuscitation, 15 minutes later ventricular fibrillation developed and the emergency physician carried out intubation and repeated defibrillation. During the next few hours a stabilization of the circulatory system was achieved. Five days after the cardiac arrest brain death occurred. The postmortem findings on the heart (only a heart section was performed) showed extensive circular hemorrhagic subendocardial necrosis with initial organization of the left ventricular wall and the septum with a well-preserved subendocardial area. In the right ventricular wall only a few small areas of organization were observed. All lesions were consistent with the cardiac arrest suffered 5 days previously. The morphological changes differ from those of a usual hemorrhagic infarction and of the sequences of a cardiopulmonary resuscitation. The circular subendocardial necroses occur after a cardiac arrest which exceeds the resuscitation time of the heart. They do not respect the area of coronary distribution and their hemorrhagic component develops after successful reanimation within the necrotic myocardium. |
3,791 | K(ATP) channel opening during ischemia: effects on myocardial noradrenaline release and ventricular arrhythmias. | Cardioprotection by K(ATP) channel openers during ischemia is well documented although ill understood. Proarrhythmic effects may be an important drawback. K(ATP) channel modulation influences neurotransmitter release during ischemia in brain synaptosomes. Therefore, we studied the effects of K(ATP) channel modulation on myocardial noradrenaline release and arrhythmias in ischemic rabbit hearts. Isolated rabbit hearts were perfused according to Langendorff and stimulated. Local electrograms were recorded and K+-selective electrodes were inserted in the left ventricular free wall. Cromakalim (3 microM) or glibenclamide (3 microM) was added 20 min prior to induction of global ischemia. After 15, 20, or 30 min of ischemia, hearts were reperfused and noradrenaline content of the first 100 ml of reperfusate was measured. Cromakalim (n = 16) prevented the second rise of extracellular [K(+)] in accordance with its cardioprotective effect. Cromakalim significantly reduced noradrenaline release after 15 min (mean, 169 +/- SEM 97 pmol/gr dry weight vs. control 941 +/- 278; p < 0.05) and 20 min of ischemia (230 +/- 125 pmol/gr dry wt vs. control 1,460 +/- 433; p < 0.05), but after 30 min of ischemia, the difference in noradrenaline release was no longer significant (cromakalim 2,703 +/- 1,195 pmol/gr dry wt vs. control 5,413 +/- 1,310; p = 0.08). Ventricular fibrillation or ventricular tachycardia occurred in 10 of 13 control hearts (77%) (n = 19), in six of 10 glibenclamide-treated hearts (60%) (n = 15), and in six of 14 cromakalim-treated hearts (43%) (p = NS). Cromakalim significantly accelerated onset of ventricular tachycardia or fibrillation (mean +/- SEM onset after 12.5 +/- 1.6 min ischemia vs. control 16.2 +/- 0.7 min; p < 0.05). Noradrenaline release occurred only in cromakalim-treated hearts with early-onset arrhythmias whereas no noradrenaline release was observed in cromakalim-treated hearts without ventricular tachycardia or fibrillation. Our results show that activation of the K(ATP) channel by cromakalim during ischemia reduces myocardial noradrenaline release and postpones the onset of irreversible damage, contributing to the cardioprotective potential of K(ATP) openers during myocardial ischemia. |
3,792 | Cooling for acute ischemic brain damage (cool aid): an open pilot study of induced hypothermia in acute ischemic stroke. | Hypothermia is effective in improving outcome in experimental models of brain infarction. We studied the feasibility and safety of hypothermia in patients with acute ischemic stroke treated with thrombolysis.</AbstractText>An open study design was used. All patients presented with major ischemic stroke (National Institutes of Health Stroke Scale [NIHSS] score >15) within 6 hours of onset. After informed consent, patients with a persistent NIHSS score of >8 were treated with hypothermia to 32+/-1 degrees C for 12 to 72 hours depending on vessel patency. All patients were monitored in the neurocritical care unit for complications. A modified Rankin Scale was measured at 90 days and compared with concurrent controls.</AbstractText>Ten patients with a mean age of 71.1+/-14.3 years and an NIHSS score of 19.8+/-3.3 were treated with hypothermia. Nine patients served as concurrent controls. The mean time from symptom onset to thrombolysis was 3.1+/-1.4 hours and from symptom onset to initiation of hypothermia was 6.2+/-1.3 hours. The mean duration of hypothermia was 47.4+/-20.4 hours. Target temperature was achieved in 3.5+/-1.5 hours. Noncritical complications in hypothermia patients included bradycardia (n=5), ventricular ectopy (n=3), hypotension (n=3), melena (n=2), fever after rewarming (n=3), and infections (n=4). Four patients with chronic atrial fibrillation developed rapid ventricular rate, which was noncritical in 2 and critical in 2 patients. Three patients had myocardial infarctions without sequelae. There were 3 deaths in patients undergoing hypothermia. The mean modified Rankin Scale score at 3 months in hypothermia patients was 3.1+/-2.3.</AbstractText>Induced hypothermia appears feasible and safe in patients with acute ischemic stroke even after thrombolysis. Refinements of the cooling process, optimal target temperature, duration of therapy, and, most important, clinical efficacy, require further study.</AbstractText> |
3,793 | Sotalol: the mechanism of its antiarrhythmic-defibrillating effect. | This minireview deals with the role of intercellular communication and synchronization in the initiation and maintenance of ventricular fibrillation. It is proposed that myocardial cell junctions might represent a therapeutic substrate for the prevention of this fatal arrhythmia. This hypothesis is supported by the results of recent experimental studies involving elucidation of the mechanism of antiarrhythmic-defibrillating effects of sotalol. Enhancement of intercellular communication and myocardial synchronization are thought to play critical role in the mechanism of action of this drug. |
3,794 | Multilateral in vivo and in vitro protective effects of the novel heat shock protein coinducer, bimoclomol: results of preclinical studies. | Bimoclomol, the recently developed non-toxic heat shock protein (HSP) coinducer, was shown to display multilateral protective activities against various forms of stress or injuries at the level of the cell, tissue or organism. The compound enhanced the transcription, translation and expression of the 70 kD heat shock protein (HSP-70) in myogenic and HeLa cell lines exposed to heat stress, and increased cell survival on exposure to otherwise lethal thermal injury. Bimoclomol increased contractility of the working mammalian heart, this effect was associated with the increased intracellular calcium transients due to increased probability of opening of ryanodine receptors in the sarcoplasmic reticulum (SR). In healthy tissues these cardiac effects were evident only at relatively high concentrations of the drug, while in the ischemic myocardium bimoclomol exerted significant cardioprotective and antiarrhythmic effects at submicromolar concentrations. It decreased ischemia-induced reduction of contractility and of cardiac output, and dramatically decreased the elevation of the ST-segment during ischemia as well as the occurrence of ventricular fibrillation upon reperfusion. Bimoclomol was also active in various pathological animal models subjected to acute or chronic stress. In the spontaneously hypertensive rats chronic pretreatment with bimoclomol restored sensitivity of aortic rings to acetylcholine; this effect was accompanied by accumulation of HSP-70 in the tissues. Bimoclomol pretreatment significantly diminished the consequences of vascular disorders associated with diabetes mellitus. Diabetic neuropathy, retinopathy, and nephropathy were prevented or diminished, while wound healing was enhanced by bimoclomol. Enhancement of wound healing by bimoclomol was observed after thermal injury as well as following ultraviolet (UV) irradiation. In addition to the beneficial effects on peripheral angiopathies, bimoclomol antagonized the increase in permeability of blood-brain barrier induced by subarachnoid hemorrhager or arachidonic acid. A general and very important feature of the above effects of bimoclomol was that the drug failed to cause alterations under physiological conditions (except the enhanced calcium release from cardiac sarcoplasmic reticulum). Bimoclomol was effective only under conditions of stress. Consistent with its HSP-coinducer property, bimoclomol alone had very little effect on HSP production. Its protective activity became apparent only in the presence of cell damage. Currently, bimoclomol reached the end of the Phase II clinical trial in a group of 410 patients with diabetic complications. Results of this trial will answer the question, whether a compound with promising in vitro and in vivo preclinical findings will produce the anticipated beneficial effects in humans. In the event of a positive outcome of this trial, the indications for bimoclomol will be substantially extended. |
3,795 | Effects of biphasic vs monophasic defibrillation on the scaling exponent in a swine model of prolonged ventricular fibrillation. | Mathematical analyses of ventricular fibrillation (VF) have resulted in the derivation of a measure termed the scaling exponent (ScE) that characterizes the duration of VF and probability of defibrillation success. The purpose of this study was to compare the effects of biphasic defibrillation waveform (BDW) and monophasic defibrillation waveform (MDW) rescue shocks on ScE in a swine model of prolonged VF.</AbstractText>Utstein guidelines for the laboratory study of cardiopulmonary resuscitation were followed. Twenty mixed-breed domestic swine (mass range 20.5-26.8 kg) were instrumented and randomized to receive either MDW or BDW rescue shocks. Ventricular fibrillation was induced and untreated for a nonintervention interval of 8 minutes. Rescue shocks were delivered at 8, 10, and 12 minutes of elapsed VF time. The energy sequence for the three MDW shocks was 70, 100, and 150 J (approximately 3, 4, and 6 J/kg). All BDW shocks were delivered at 50 J (approximately 2.5 J/kg). Only VF was shocked. Chest compressions and drugs were not provided. Rhythm analysis and ScE calculation were performed offline. Continuous and discontinuous linear regression models were fit to plots of ScE vs time. Defibrillation success and progression of ScE slope were analyzed using Fisher's exact test, paired t-tests, and repeated-measures analysis of variance (ANOVA).</AbstractText>Baseline characteristics were similar for both groups. Successful termination of VF occurred on the first rescue shock in 1 of 10 (10%) in the MDW group and 3 of 10 (30%) in the BDW group; this difference was not statistically significant (p = 0.58). No other defibrillation successes were observed. No animals achieved return of spontaneous circulation. The ScE values during the protocol progressed from 1.330 (95% CI = 1.287 to 1.373) to 1.724 (95% CI = 1.603 to 1.845) for MDW and 1.338 (95% CI = 1.261 to 1.415) to 1.639 (95% CI = 1.530 to 1.745) for BDW. Both groups showed a trend toward increasing ScE values with successive rescue shocks. Repeated-measures ANOVA using both continuous and discontinuous models demonstrated no difference in overall ScE slope progression between study groups.</AbstractText>Mode of defibrillation waveform (BDW vs MDW) does not appear to impact ScE trends. Additional studies must be performed to better evaluate the clinical implications of this finding.</AbstractText> |
3,796 | Management of cardiac arrhythmias in acute coronary syndromes. | A variety of atrial and ventricular arrhythmias are encountered in patients with acute coronary syndromes. These include both brady and tachyarrhythmias of supraventricular and ventricular origin. Sinus bradycardia and atrial fibrillation are the most common of supraventricular origin. Ventricular arrhythmias that merit consideration include premature ventricular complexes, accelerated idioventricular rhythm, ventricular tachycardia, and ventricular fibrillation. Intraventricular and atrioventricular conduction blocks associated with acute coronary syndromes include bundle branch blocks, fascicular blocks, and various degrees of atrioventricular block. A review of management of these arrhythmias is presented. |
3,797 | Clinical assessment of clonidine in the treatment of new-onset rapid atrial fibrillation: a prospective, randomized clinical trial. | The role of digoxin and verapamil in the control of ventricular response in rapid atrial fibrillation is well established. This study investigates how clonidine compares with these standard therapies in rate control for new-onset rapid atrial fibrillation. We set out to test the hypothesis that clonidine effectively reduces heart rate in patients with new-onset rapid atrial fibrillation.</AbstractText>Forty patients were seen in the emergency department with new-onset (< or =24 hours' duration), stable, rapid atrial fibrillation. Eligible patients were randomized to receive either clonidine, digoxin, or verapamil. Changes in heart rate and blood pressure over 6 hours, as well as frequency of conversion to sinus rhythm were recorded and analyzed.</AbstractText>The mean reduction in heart rate over 6 hours was 44.4 beats/min (95% confidence interval [CI] 28.4-60.4 beats/min) in the clonidine group, 52.1 beats/min (95% CI 40.8-63.4 beats/min) in the digoxin group, and 41.8 beats/min (95% CI 22.5-61.0 beats/min) in the verapamil group. Analysis of variance of the heart rate changes in the 3 groups after 6 hours was not significant (P =.55). At 6 hours, 7 of 12 clonidine patients, 8 of 15 digoxin patients, and 7 of 13 verapamil patients remained in atrial fibrillation (P =.962 on chi(2)).</AbstractText>Clonidine controls ventricular rate in new-onset atrial fibrillation with an efficacy comparable to that of standard agents.</AbstractText> |
3,798 | Safety and feasibility of a novel rate-smoothed ventricular pacing algorithm for atrial fibrillation. | This study was conducted to establish the safety and performance of a new rate-smoothing pacing algorithm for patients with atrial fibrillation (AF).</AbstractText>Irregularity of the ventricular response is a hallmark of AF. This irregularity may contribute to symptoms and hemodynamic compromise in patients with AF. Interventions designed to reduce irregularity have not previously been evaluated in a long-term, clinical setting.</AbstractText>We designed a prospective, double-blind study with randomized crossover. Patients with either paroxysmal or chronic AF whose conditions were medically refractory and who were referred for an atrioventricular node ablation procedure all underwent pacemaker implantation. Subjects were then randomly assigned to either DDD mode with the rate-smoothing algorithm (RSA) on, or to OOO mode. After 2 months they were crossed over to the other arm.</AbstractText>Fourteen patients (9 with paroxysmal AF and 5 with chronic AF) were enrolled. There were no significant differences between the group randomly assigned to RSA first versus the group assigned to OOO first. The mean left ventricular ejection fraction with the RSA was not significantly different than it was in OOO mode (45.1 +/- 18.6 vs 51.9 +/- 12.3; P =.11), although some individuals with uncontrolled ventricular rates did have a large decrease in ejection fraction with rate smoothing. One developed overt heart failure. One quality-of-life instrument detected a significant improvement in the "physical limitations" domain with the rate-smoothing mode. Eleven of 14 patients preferred the RSA ON arm, and 6 of those 11 elected to defer the ablation procedure.</AbstractText>Long-term rate-smoothed pacing is feasible. Because of concerns about pacing-induced heart failure in some patients with rapid ventricular rates, rate-smoothed pacing should be reserved for those who remain symptomatic despite adequate control of the ventricular rate. The RSA may help to reduce symptoms in patients with medically refractory AF; more study is required to define its efficacy in reducing symptoms and morbidity in this population.</AbstractText> |
3,799 | Management of the critically ill cardiac patient. | The decline in rheumatic fever has made heart disease in pregnancy an uncommon problem in the developed world but it remains an important cause of maternal morbidity and mortality in developing countries. Pregnancy is particularly dangerous in the presence of cyanotic congenital heart disease, Eisenmenger's syndrome, primary pulmonary hypertension, Marfan's syndrome, dilated cardiomyopathy and significant mitral stenosis. Severe stenosis is often complicated by pulmonary hypertension and atrial fibrillation. Maternal disease status should be determined using echocardiography to define cardiac anatomy, assess ventricular function and estimate intracardiac pressure gradients. Patients in the New York Heart Association functional classes 1 and 2 generally have a favourable outcome. Closed mitral commissurotomy is safe and effective in relieving stenosis across the mitral valve in selected patients. More recently the technique of percutaneous balloon mitral valvotomy has successfully been used in the treatment of mitral stenosis. Termination of pregnancy is advised in patients with severe pulmonary hypertension, including Eisenmenger's syndrome. |
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