Effects of flecainide and quinidine on human atrial action potentials. Role of rate-dependence and comparison with guinea pig, rabbit, and dog tissues
Abstract
Flecainide and other class IC antiarrhythmic drugs are effective in the prevention and termination of atrial fibrillation, but the mechanism of this action is unknown. To gain insights into potential cellular mechanisms, we evaluated the response of human atrial action potentials to equimolar therapeutic concentrations of flecainide and quinidine and compared this response to that of guinea pig, rabbit, and dog atria. Both compounds reduced Vmax more as activation rate increased, but flecainide was more potent than quinidine and had slower kinetics. The rate-dependence of Vmax reduction was similar for all species, but human tissue was more sensitive to the drugs tested. In contrast to changes in Vmax, drug-induced alterations in action potential duration showed opposite rate-dependence for the two drugs. Quinidine increased action potential duration to 95% repolarization (APD95) in human atria by 33 +/- 7% (mean +/- SD) at a cycle length of 1,000 msec, but this effect was reduced as cycle length decreased, to 12 +/- 4% (p less than 0.001) at a cycle length of 300 msec. Flecainide increased APD95 (by 6 +/- 3%) much less than quinidine at a cycle length of 1,000 msec, but its effect was increased by faster pacing, to 27 +/- 12% ...Continue Reading
References
Effects of quinidine on action potentials and ionic currents in isolated canine ventricular myocytes
Citations
Electrophysiological effects of flecainide acetate on stretched guinea pig left atrial muscle fibers
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