Increasing the effective interstitial resistivity promotes the escape of premature beats

Ectopic beats in the heart require a heterogeneous substrate to develop into dangerous, whole-heart arrhythmias. In this study, a 1-D monodomain computer model that incorporated local heterogeneity in both the interstitial and intracellular spaces was used to investigate whether increased interstitial resistivity could modulate the escape of premature beats given at different coupling intervals. Our simulations show that locally increasing the effective interstitial resistivity (¿_oeff) reduces both the conduction delay and the dispersion of repolarization at the boundary between the poorly-coupled and well-coupled regions. Increasing ¿_oeff also decreases the dependence of the conduction delay on the coupling beat interval. The interaction between microheterogeneity in the interstitial and intracellular spaces may increase the likelihood that premature ectopic beats will escape and trigger an arrhyhmia.