Heart rate variability and stroke or systemic embolism in patients with atrial fibrillation

BACKGROUND: Stroke remains one of the most serious complications in atrial fibrillation (AF) patients and has been linked to disturbances of the autonomic nervous system. OBJECTIVE: The purpose of this study was to test the hypothesis that impaired cardiac autonomic function might be associated with an enhanced stroke risk in AF patients. METHODS: A total of 1922 AF patients who were in either sinus rhythm (SR group; n = 1121) or AF (AF group; n = 801) on a 5-minute resting electrocardiographic (ECG) recording were enrolled in the study. Heart rate variability triangular index (HRVI), standard deviation of normal-to-normal intervals, root mean square root of successive differences of normal-to-normal intervals, mean heart rate, 5-minute total power, and power in the high-frequency, low-frequency, and very-low-frequency ranges were calculated. Cox regression models were constructed to examine the association of heart rate variability (HRV) parameters with the composite endpoint of stroke or systemic embolism. RESULTS: Mean age was 71 ± 8 years in the SR group and 75 ± 8 years in the AF group. Thirty-seven patients in the SR group (3.4%) and 60 patients in the AF group (8.0%) experienced a stroke or systemic embolism during follow-up of 5 years. In patients with SR, HRVI <15 was the strongest HRV parameter to be associated with stroke or systemic embolism (hazard ratio 3.04; 95% confidence interval 1.3-7.0; P = .009) after adjustment for multiple confounders. In the AF group, no HRV parameter was found to be associated with the composite endpoint. CONCLUSION: HRVI measured during SR on a single 5-minute ECG recording is independently associated with stroke or systemic embolism in AF patients. HRV analysis in SR may help to improve risk stratification in AF patients.