Abstract
BackgroundAutonomic dysfunction appears to play a significant role in the development of atrial fibrillation (AF), and impaired heart rate recovery (HRR) during exercise treadmill testing (ETT) is a known marker for autonomic dysfunction. However, whether impaired HRR is associated with incident AF is unknown. We studied the association of impaired HRR with the development of incident AF, after controlling for demographic and clinical confounders.MethodsWe studied 8236 patients referred for ETT between 2001 and 2004, and without a prior history of AF. Patients were categorized by normal or impaired HRR on ETT. The primary outcome was the development of AF. Cox proportional hazards modeling was used to control for demographic and clinical characteristics. Secondary analyses exploring a continuous relationship between impaired HRR and AF, and exploring interactions between cardiac medication use, HRR, and AF were also conducted.ResultsAfter adjustment, patients with impaired HRR were more likely to develop AF than patients with normal HRR (HR 1.43, 95% confidence interval (CI) 1.06, 1.93). In addition, there was a linear trend between impaired HRR and AF (HR 1.05 for each decreasing BPM in HRR, 95% CI 0.99, 1.11). No interactions between cardiac medications, HRR, and AF were noted.ConclusionPatients with impaired HRR on ETT were more likely to develop new-onset AF, as compared to patients with normal HRR. These findings support the hypothesis that autonomic dysfunction mediates the development of AF, and suggest that interventions known to improve HRR, such as exercise training, may delay or prevent AF.
Highlights
Autonomic dysfunction appears to play a significant role in the development of atrial fibrillation (AF), and impaired heart rate recovery (HRR) during exercise treadmill testing (ETT) is a known marker for autonomic dysfunction
After adjustment for age and gender, impaired HRR was significantly associated with a higher risk of new-onset AF (hazard ratio (HR) 1.55, 95% confidence interval (CI) 1.15, 2.08), as compared to patients with normal HRR (Table 2)
After adjustment for age, gender, and clinical factors, impaired HRR remained significantly associated with a higher risk of new-onset AF (HR 1.43, 95% CI 1.06, 1.93), as compared to patients with normal HRR (Table 2)
Summary
Autonomic dysfunction appears to play a significant role in the development of atrial fibrillation (AF), and impaired heart rate recovery (HRR) during exercise treadmill testing (ETT) is a known marker for autonomic dysfunction. We studied the association of impaired HRR with the development of incident AF, after controlling for demographic and clinical confounders. Atrial fibrillation (AF) is a common condition in the U.S, with over 75,000 new cases annually.[1] Though its etiology is multi-factorial, prior mechanistic studies have demonstrated that autonomic dysfunction in general, and decreased parasympathetic function in particular, may play a significant role in its development. Exercise treadmill testing (ETT) is a widely available clinical tool that provides an assessment of autonomic dysfunction via measurement of heart rate recovery (HRR). Demonstration of an association between AF and impaired HRR during ETT would add to the basic physiologic, animal, and clinical observation studies supporting the concept of the autonomic nervous system as a potential mediator of AF.[2]
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