Submitted on January 4, 2007
Accepted on June 15, 2007
The Pinwheel Experiment Revisited:
Effects of Cellular Electrophysiological Properties on Vulnerability to Cardiac Reentry
Ming-Jim Yang1, Diana X Tran1, James N. Weiss2, Alan Garfinkel3, and Zhilin Qu3*
1 Physiological Science, University of California, Los Angeles, Los Angeles, California, United States
2 Division of Cardiology, University of California School of Medicine, Los Angeles, California, United States
3 Medicine, University of California, Los Angeles, Los Angeles, California, United States
* To whom correspondence should be addressed. E-mail: zqu{at}mednet.ucla.edu.
In normal heart, ventricular fibrillation can be induced by a single properly-timed strong electrical or mechanical stimulus. A mechanism first proposed by Winfree and coined the "pinwheel experiment" emphasizes the timing and strength of the stimulus in inducing figure-of-eight reentry. However, the effects of cellular electrophysiological properties on vulnerability to reentry in the pinwheel scenario have not been investigated. In this study, we extend Winfree's pinwheel experiment to show how the vulnerability to reentry is affected by the graded action potential responses induced by a strong premature stimulus, action potential duration (APD), and APD restitution in simulated monodomain homogeneous two-dimensional tissue. We find that a larger graded response, longer APD, or steeper APD restitution slope reduce the vulnerable window of reentry. Strong graded responses and long APD promote tip-tip interactions at long coupling intervals, causing the two initiated spiral wave tips to annihilate. Steep APD restitution promotes wavefront-waveback interaction, causing conduction block in the central common pathway of figure-of-eight reentry. We derive an analytical treatment which shows good agreement with numerical simulation results.
