Reflection and ectopic activity induced by early after depolarizations. A computer modeling study

A computer model of two partially coupled ventricular fibers was used to study conditions in which EADs developed in an area of ventricular myocardium propagate to other areas, generating ectopic activity or reflection. We simulate the interactions between two areas of myocardium coupled through an area of unexcitable tissue, simulated by a resistance R. EADs are induced in one of the segments by enhancing I/sub Ca/ current and decreasing I/sub K/ current while the other is kept under normal conditions. The results show that the likelihood of ectopic activity and reflection depends on both EAD conditions and R values. For low values of R (in the range from 5 /spl Omega//spl middot/cm/sup 2/ to 10 /spl Omega//spl middot/cm/sup 2/) ectopic activity and reflection only appear for strong EAD conditions (I/sub Ca/ enhanced by 80% and I/sub K/ blocked by 80%). However, when higher R values are used, the ectopic activity and reflection appear at less extreme EAD conditions. For R=50 /spl Omega//spl middot/cm/sup 2/, both phenomena appear for I/sub Ca/ enhanced by 60% and I/sub K/ blocked by 60%. The study shows that ectopic activity and reflection in a zone of myocardium could be induced by EADs generated in neighboring zones.