Arrhythmogenesis, the electrophysiologic matrix, and electrophysiologic chaos

Cardiac arrhythmias are a major health threat. Multiplicities, discontinuities, dynamic interactions, and other complexities that exist among the determinants of cardiac excitability should give rise to unpredictably complex behavior, yet electrophysiologic events are unusually sufficiently coordinated to produce predictable outcomes. Theoretical and experimental work is discussed in terms of the electrophysiologic matrix and assisted bifurcations, which show how complex systems can act simply to produce order out of apparent chaos. We propose that altered excitability underlies abnormal impulse propagation and formation. The increased prominence of anisotropy and functional block in reentrant arrhythmias is noted, with emphasis placed on cell-to-cell communication. Important work on the effects of stretch, the autonomic nervous system and central events, triggered automaticity, and both biochemical and metabolic alterations to arrhythmias is reviewed. New methodologies for the study of arrhythmias are also mentioned. Finally, new work is cited relating the importance of nonlinear dynamics to cardiac excitability, impulse propagation, and entrainment.