The role of cellular discontinuities in reentry of cardiac excitation

A computer model of a ring-shaped cardiac fiber was used to examine responses of propagation to premature stimuli under different degrees of cell-to-cell coupling. Nonsustained and sustained reentry were induced by a properly timed single premature stimulus. The likelihood of inducing reentry is proportional to the degree of cellular uncoupling. Modified kinetics of slow channels bring about shortening of action potential duration and alternations in action potential shape (alternans). The authors conclude that the discrete cellular structure may play an important role in the genesis of reentrant arrhythmias.<>