The effect of critical point location and membrane kinetics on VF induction by T-wave stimulation

A strong stimulus delivered in the T-wave of a normal cardiac cycle can induce ventricular fibrillation. The critical point mechanism is thought to be responsible for this phenomenon. However, rapid pacing can cause an otherwise benign strong T-wave stimulus to induce VF. In this paper, we examine an extension of the critical point hypothesis which can explain the effect of rapid pacing. Specifically, we hypothesize that a critical point must form a minimum distance from an anatomical obstacle to establish VF. Furthermore, we suspect that this minimum distance depends on the pacing rate prior to the stimulus. The FitzHugh-Nagumo membrane kinetics and advanced solving techniques (EZ-Spiral) were used to simulate the dynamics of spiral waves and critical points in excitable media. The model confirms a distance / pacing rate interaction, but also indicates a subtle difference in the form of reentry initiated after rapid pacing.