[Myocardial parameters controlling vulnerability. Analysis of mathematical models]

Vulnerability induced by application of a properly timed premature stimulus was studied on mathematical models. Two mechanisms of vulnerability 1) reentry, 2) focal reexcitation were analysed. Tissue with a region of increased refractory period Rmax was simulated on Wiener's type model. The influence of high refractoriness region dimensions and tissue parameters on the duration of vulnarable period was studied. Reentry was shown to appear on the border of high refractoriness region, which minimal length lmin being the shorter, the greater was tau (maximal latency of response) and epsilon (epsilon = deltaR/R--degree of heterogeneity). The dependence of vulnerable period duration on current strength was computed for Nobel's model. The dip-phenomenon was found in this model, the vulnerable zone was located above the minimal value of threshold.