The role of the autonomic nervous system in cardiac arrhythmias.

Autonomic nervous system activity exerts potent and diverse effects on cardiac rhythm through elaborate neurocircuitry that is integrated at multiple levels. Adrenergic activity such as is associated with mental or physical stress or as a reflex response to myocardial ischemia is capable of generating significant rhythm abnormalities including ventricular fibrillation, the arrhythmia responsible for sudden cardiac death. With respect to the ventricles, vagus nerve activity is generally antiarrhythmic as it inhibits the profibrillatory effects of sympathetic nerve activation, whereas atrial arrhythmias generally derive from heightened levels of both vagus and sympathetic nerve activity. Containment of neural influences by pharmacological and electrical targeted neuromodulation is being pursued as an antiarrhythmic modality.