tokens: RESULTS : Verapamil caused AF promotion in six dogs , increasing mean duration of AF induced by burst pacing , from 8 + / - 4 s ( mean + / - S . E . ) to 95 + / - 39 s ( P < 0 . 01 vs . control ) at a loading dose of 0 . 1 mg / kg and 228 + / - 101 s ( P < 0 . 0005 vs . control ) at a dose of 0 . 2 mg / kg .