Cardiac autonomic function in elderly patients with and without atrial fibrillation

Cardiac autonomic dysfunction is associated with an adverse prognosis in patients with atrial fibrillation (AF). However, the association of AF itself with cardiac autonomic function (CAF) remains unclear. We aimed to investigate whether CAF, assessed by heart rate variability (HRV), differs across patients with and without AF.

We enrolled patients from a prospective multicentre study (Swiss-AF) with a 5-min resting ECG recording in SR or AF without pacing. Cardiac autonomic function was quantified by periodic repolarization dynamics (PRD), a marker of sympathetic activity, and by conventional HRV parameters. We included 2289 patients, 807 (35%) SR patients, 932 (41%) AF patients with SR ECGs (AF-SR), and 550 (24%) AF patients with AF ECGs (AF-AF). Mean age was 74 vs. 70 vs. 75 years; 37%, 31%, and 24% were female. Median PRD was 4.8 deg (IQR 2.6-6.7) in the SR group, 5.1 deg (IQR 2.9-6.9) in the AF-SR group, and 7.0 deg (IQR 5.8-8.4) in the AF-AF group (P < 0.001). After full adjustment (SR group = reference group), the AF-AF group showed a stronger association with elevated PRD (β-coefficient 2.10, 95% CI 1.79-2.41, P < 0.001) than the AF-SR group (β-coefficient 0.36, 95% CI 0.08-0.64, P = 0.011). Most other HRV parameters indicated greater autonomic impairment in the AF-SR group compared to the SR group.

Atrial fibrillation was associated with increased sympathetic activity, with the greatest impairment observed in patients during AF, independent of cardiovascular risk factors. Periodic repolarization dynamics may represent a useful marker for the assessment of CAF in AF patients.