Neural mechanisms involved in the regulation of ventricular repolarization

Neural mechanisms have important influences on ventricular repolarization. The normal gradients of repolarization such as that from long to short duration on the endocardial-epicardial axis are probably not the result of nonuniform neural effects. The ventricular distributions of individual cardiac sympathetic nerves is, however, localized and provides a possible basis for nonuniform effects on repolarization in various disease states. Such localized sympathetic effects are the probable mechanism of electrocardiographic waveform abnormalities associated with neurologic disease and a possible mechanism of the idiopathic prolonged QT interval syndromes. The medical significance of nonuniform neural influences on ventricular repolarization includes the evaluation of neurogenic electrocardiographic waveform abnormalities that may be erroneously attributed to intrinsic heart disease. Of greater importance, nonuniform repolarization has established relations to cardiac arrhythmias including ventricular fibrillation and nonuniform sympathetic effects on repolarization may be a significant factor in the occurrence and persistence of these disorders. Parasympathetic influences on ventricular repolarization are slight compared to sympathetic effects and may operate by opposing adrenergic effects.