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

BACKGROUND Stroke remains one of the most serious complications in atrial fi brillation (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 5minute 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 fi dence 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 fi cation in AF patients.