Prospective Association of Incident Atrial Fibrillation With Resting Heart Rate: The Henry Ford Hospital Exercise Testing (FIT) project

Objective: Autonomic nervous system dysfunction plays an important role in atrial fibrillation (AF) initiation. Research suggests that vagal tone may mediate paroxysmal AF, such that a low resting heart rate (RHR) is associated with incident AF. However, conflicting reports also suggest that elevated RHR identifies risk for AF. Thus, we sought to further clarify the link between RHR and AF, independent of cardiorespiratory fitness (CRF). Methods: We analyzed 51,451 individuals without a history of AF who underwent a clinically-indicated exercise stress test between January 1991 and May 2009. Persons on nodal blocking medications were excluded. Adjusted hazard ratios (HRs) for AF were estimated using Cox models with baseline RHR categorized by 85 beats-per-minute (bpm) (sensitivity analyses used quartile of RHR). Incident AF was defined by coding for new AF on claims files on ≥three subsequent encounters. We tested for effect modification by age (u003c60 vs. ≥60 years) and CRF (dete...