Fractal mechanisms in the electrophysiology of the heart

Fractals are defined, and the fractal-like anatomy of the heart is described. The concept of the healthy heartbeat as a temporal fractal is examined at two specific levels of cardiac function: ventricular depolarization and heart rate regulation. It is suggested that complex fluctuations in healthy heart rate may be due in part to deterministic chaos in the neuroautonomic control system. Furthermore, perturbations of this control system, such as those seen in heart failure and in sudden cardiac death syndromes, may lead to a loss of complexity of heart rate dynamics.