Effects of channel blockers on reentrant arrhythmias: model study

The authors employ a bifurcation analysis approach to ascertain the effects of various classes of antiarrhythmic drugs and explain why some antiarrhythmic drugs could be proarrhythmic. This is done by constructing the bifurcation diagram between conduction velocity and ring size, which reveals a phase transition. At this phase transition, the infinite ring behavior breaks down, and reentry becomes unstable. Instability in reentry causes oscillations in action potential duration, cycle length, and conduction velocity, with interesting patterns whose period of oscillations depends on the ring site. The bifurcation diagram furthermore reveals that the channel blockers affects the phase transition point in different manners. This differential explains why some Na/sup +/ and Ca/sup 2+/ channel blockers are proarrhythmic while K/sup +/ channel blockers are not. The prediction from the bifurcation diagram is in agreement with experiments in canine atrial tricuspid ring in vitro.<>