Mechanism by which pacing rate affects the upper limit of ventricular vulnerability to fibrillation by T-wave stimulation

A stimulus in the T-wave of the heart's normal cycle can alter the heart's activity. However, there is an upper limit (ULV) to stimulus strength that can cause conversion to ventricular fibrillation (VF). Since the ULV is correlated with the defibrillation threshold, it might be a safer alternative or adjunct to clinical defibrillation efficacy testing and may give insights into defibrillation mechanisms. This work demonstrates that the ULV is sensitive to the number and rate of proceeding paced beats. Possible mechanisms for this dependence are presented, perhaps giving insights into defibrillation.