Dynamic mechanism for conduction block in heart tissue

Previous work has shown that dynamic heterogeneity and conduction block can occur in homogeneous heart fibres during prolonged pacing at rapid rates. Here we investigated the mechanism for conduction block following the delivery of one to four premature stimuli using a coupled maps computer model of a one-dimensional canine heart fibre. The coupled maps model allowed us to identify the roles that velocity (V) restitution, action potential duration (D) restitution and cardiac memory (M) played in the development of spatial heterogeneity and conduction block. We found that the likelihood of conduction block could be reduced by three methods. (1) By altering the V restitution function so that conduction slowed at very short rest intervals (I). (2) By altering the D restitution function to reduce the sensitivity of D to changes in I. (3) By increasing the contribution of cardiac memory (M). Although the results of this study need to be confirmed experimentally, they suggest several potential interventions that may reduce the probability of arrhythmia induction.