Afib and the autonomic nervous system
In 1982 (27 years ago!) Dr. Philippe Coumel of the Lariboisiere Hospital in Paris discovered that a dysfunction of the autonomic nervous system (ANS) plays a major role in lone atrial fibrillation (LAF). Dr. Coumel coined the terms vagal and adrenergic to describe two types of afib – one associated with an overactive parasympathetic (vagal) branch of the ANS, and the other associated with an overactive sympathetic (adrenergic) branch. For many years, Dr. Coumel's findings were ignored (especially in North America) and cardiologists lumped all cases of afib together as adrenergic with often disastrous results such as prescribing beta-blockers for vagal afibbers.

The tide has now turned with most electrophysiologists and, to a lesser extent, cardiologists recognizing the existence of the two types and adjusting their prescription patterns accordingly. German researchers recently provided additional evidence of the association between the ANS and LAF. From a total of over 20,000 consecutive Holter recordings they identified 715 episodes of paroxysmal afib. They found that 41% were preceded by a run of ectopic beats, 29% were of sudden onset, and 20% were preceded by a change in heart rate (possibly bradycardia as experienced by vagal afibbers whilst at rest). By analyzing heart rate variability (HRV) in 5-minute segments just prior to the onset of an episode, the researchers discovered that sudden onset episodes were associated with significant changes in HRV just prior to onset. Thus, the low frequency component (adrenergic) and the low frequency/high frequency (adrenergic/vagal) ratio increased significantly as did the Poincare plot index. The researchers conclude that transient abnormal fluctuations in cardiac ANS control may predispose to the development of paroxysmal afib.

Circulation, Vol. 118, No. 18S, October 28, 2008, Abstract #1037