Duration of heart failure and the risk of atrial fibrillation: different mechanisms at different times?

Chronic heart failure increases the risk of atrial fibrillation (AF), with the prevalence of AF paralleling the severity of heart failure.1 Factors that underlie this increased susceptibility to AF may include electrical, structural, and neurohumoral changes.2 In AF, it is recognized that atrial electrophysiological remodelling occurs and contributes to the perpetuation of the arrhythmia, most notably the decrease of effective refractory period (ERP) which predisposes to re-entry by shortening the wavelength. Does heart failure cause similar changes in atrial electrophysiology that predispose to the arrhythmia?An extensively studied dog model, in which heart failure was induced by rapid ventricular pacing, has suggested not: atrial electrophysiological changes were either absent, or were in the opposite direction, with prolongation of the action potential duration (APD).3,4 Susceptibility to induced AF was increased, but this was more related to structural changes, in particular increased fibrosis,5 than electrophysiological properties. In contrast, our recent study of human right atrial isolated myocytes6 found that left ventricular (LV) systolic dysfunction was associated with electrophysiological changes—decreased APD and shortened refractoriness—which would predispose to AF, contrary to the findings in the dog model.Sridhar et al. 7 shed some light on this discrepancy, indicating that the key factor may be the duration of heart failure. The main methodological difference in the dog … *Corresponding author. Tel: +44 141 211 4833; fax: +44 141 552 4683; E-mail address : acr1a{at}clinmed.gla.ac.uk