[Autoregulation of ventricular parasystole. The triphasic phase response curve]

In the previously published examples where parasystolic rhythms were modulated and entrained, the electrotonic events came from the action potentials arising from the surrounding myocardium. In the two present cases, a ventricular parasystolic focus was entrained by the electrotonic image of the action potentials resulting from its own discharges. The electronic transmission across the protection zone being delayed, the resulting ventricular action potentials were able to automodulate, and entrain, the parasystolic focus according to a triphasic phase response curve. The development of the theory of parasystolic modulation may explain certain bizarre EKG recordings.