Refractory period dynamics and cardiac stability: results from a computer model

Computer simulations of reentrant cardiac electrical conduction were extended to include dynamics which cause alternation in refractory-period duration at high pacing rates. The simulations demonstrate that alternation increases susceptibility to fibrillation as compared to models with nonalternating refractory periods. The alternating refractory periods lead to long transients in the model which create the appearance of aperiodicity. The authors suggest that details in cellular dynamics may play an important role in determining how the heart responds to rapid pacing. A small change in these details can produce a large change in the system as a whole