Influence of electrical coupling on early afterdepolarizations in ventricular myocytes

Computer modeling is used to study the effect of electrical coupling betwee n a myocardial zone where early afterdepolarizations (EAD's) can develop an d the normal neighboring tissue, The effects of such coupling on EAD develo pment and on the likelihood of EAD propagation as an ectopic beat are studi ed, The influence on EAD formation is investigated by approximating two par tially coupled myocardial zones modeled as two active elements coupled by a junctional resistance R. For R values lower than 800 Omega cm(2), the acti on potentials are transmitted to the coupled element, and for R values high er than 850 Omega cm(2) they are blocked, in both ranges of R, when the ele ctrical coupling increases, the EAD's appear at more negative takeoff poten tials with higher amplitudes and upstrokes. The EAD's are not elicited if t he electrical coupling is too high, In a separate model of two one-dimensio nal cardiac fiber segments partially coupled by a resistance R, critical R values exist, between 42 and 54 Omega cm(2), that facilitate EAD propagatio n. These results demonstrate that in myocardial zones favorable to the form ation of EAD, the electrical coupling dramatically affects initiation of EA D and its spread to the neighboring tissue.