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Division of Cardiology, Department of Medicine, Cedars-Sinai Medical Center and David Geffen School of Medicine, University of California, Los Angeles, California 90048
Submitted 21 April 2003 ; accepted in final form 26 June 2003
The influence of nicotine in modulating vulnerability to atrial tachycardia and fibrillation (AT/AF) remains ill defined. The isolated hearts of six young (23 mo) and six old (2224 mo) male Fischer 344 rats were Langendorff perfused at 5 ml/min with oxygenated Tyrode solution at 37°C, and the whole heart was also super-fused with warmed oxygenated Tyrode solution at 15 ml/min. Nicotine prolonged the interatrial conduction time and effective refractory period that were significantly (P < 0.05) higher in the old than in the young rats in a concentration-dependent manner. Nicotine had a biphasic effect on burst atrial pacing-induced AT in both groups, increasing it at 1030 ng/ml while decreasing it at 50100 ng/ml (P < 0.01). Nicotine at 10100 ng/ml increased burst atrial pacing-induced AF in the young rats but suppressed it in the old rats (P < 0.01). Optical mapping showed the presence of multiple independent wavefronts during AF and a single periodic large wavefront during AT in both groups. Nicotine, at concentrations found in the blood of smokers (3085 ng/ml), exerts biphasic effects on inducible AT/AF in young rats and suppresses it in the old rats by causing high degrees of interatrial conduction block.
aging; atrium; conduction; refractory period
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