Autonomic aspects of arrhythmogenesis: the enduring and the new

Recent progress in understanding the role of the autonomic nervous system in the development of cardiac arrhythmias is reviewed. The focus is on the translation of basic principles of neural control of heart rhythm that have emerged from experimental studies to clinical applications.

Recent studies have made significant strides in defining the function of intrinsic cardiac innervation and the importance of nerve sprouting in electrical remodeling. A recurring theme is that heterogeneity of sympathetic innervation in response to injury is highly arrhythmogenic. In addition, both sympathetic and parasympathetic influences on ion channel activity have been found to accentuate electrical heterogeneities and thus to contribute to arrhythmogenesis in the long QT and Brugada syndromes. In the clinic, heart rate variability continues to be a useful tool in delineating pathophysiologic changes that result from the progression of heart disease and the impact of diabetic neuropathy. Heart rate turbulence, a noninvasive indicator of baroreceptor sensitivity, has emerged as a simple, practical tool to assess risk for cardiovascular mortality in patients with ischemic heart disease and heart failure. Evidence of the proarrhythmic influence of behavioral stress has been further bolstered by defibrillator discharge studies and ambulatory ECG-based T-wave alternans measurement.

The results of recent investigations underscore the importance of the autonomic influences as triggers of arrhythmia and provide important mechanistic insights into the ionic and cellular mechanisms involved.