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.

Cardiac autonomic function and cognitive performance in patients with atrial fibrillation.

BACKGROUND: Atrial fibrillation (AF) is associated with loss of cognition and dementia. Cardiac autonomic dysfunction has been linked to cognitive decline. We aimed to investigate if reduced cardiac autonomic function (CAF) is associated with cognitive impairment in AF patients. METHODS: Patients with paroxysmal, persistent and permanent AF were enrolled from a multicenter cohort study if they had AF ("AF group") or sinus rhythm ("SR group") on a baseline 5 min ECG recording. Parameters quantifying CAF (heart rate variability triangular index (HRVI), mean heart rate (MHR), RMSSD, SDNN, total power and power in the VLF, LF, HF ranges) were calculated. We used the Montreal Cognitive Assessment (MoCA) to assess global cognitive function. RESULTS: 1685 AF patients with a mean age of 73 ± 8 years, 29% females, were included. MoCA score was 24.5 ± 3.2 in the AF group (N = 710 patients) and 25.4 ± 3.2 in the SR group (N = 975 patients). After adjusting for multiple confounders, lower HRVI was associated with lower MoCA scores, both in the SR group [ß = 0.049; 95% confidence interval (CI) 0.016-0.081; p = 0.003] and in the AF group (ß = 0.068; 95% CI 0.020-0.116; p = 0.006). In the AF group, higher MHR was associated with a poorer performance in the MoCA (ß = - 0.008; 95% CI - 0.014 to - 0.002; p = 0.014). We found no convincing evidence of association for other CAF parameters with cognition. CONCLUSION: Our data suggest that impaired CAF is associated with worse cognitive performance in patients with AF. Among standard HRV parameters, HRVI might be the most promising ECG index. TRIAL REGISTRATION: ClinicalTrials.gov Identifier: NCT02105844.

Association of Heart Rate Variability With Silent Brain Infarcts in Patients With Atrial Fibrillation.

Purpose: Silent brain infarcts (SBI) are frequently detected in patients with atrial fibrillation (AF), but it is unknown whether SBI are linked to autonomic dysfunction. We aimed to explore the association of autonomic dysfunction with SBI in AF patients. Methods: 1,358 AF patients without prior stroke or TIA underwent brain MRI and 5-min resting ECG. We divided our cohort into AF patients who presented in sinus rhythm (SR-group, n = 816) or AF (AF-group, n = 542). HRV triangular index (HRVI), standard deviation of normal-to-normal intervals, mean heart rate, root mean square root of successive differences of normal-to-normal intervals, 5-min total power and power in the low frequency, high frequency and very low frequency range were calculated. Primary outcome was presence of SBI in the SR group, defined as large non-cortical or cortical infarcts. Secondary outcomes were SBI volumes and topography. Results: Mean age was 72 ± 9 years, 27% were female. SBI were detected in 10.5% of the SR group and in 19.9% of the AF group (p < 0.001). HRVI <15 was the only HRV parameter associated with the presence of SBI after adjustment for clinical covariates in the SR group [odds ratio (OR) 1.67; 95% confidence interval (CI): 1.03-2.70; p = 0.037]. HRVI <15 was associated with larger brain infarct volumes [ß (95% CI) -0.47 (-0.84; -0.09), p = 0.016] in the SR group and was more frequently observed in patients with right- than left-hemispheric SBI (p = 0.017). Conclusion: Impaired HRVI is associated with SBI in AF patients. AF patients with autonomic dysfunction might undergo systematic brain MRI screening to initiate intensified medical treatment. Clinical Trials Gov Identifier: NCT02105844.

Heart Rate Variability Triangular Index as a Predictor of Cardiovascular Mortality in Patients With Atrial Fibrillation.

Background Impaired heart rate variability (HRV) is associated with increased mortality in sinus rhythm. However, HRV has not been systematically assessed in patients with atrial fibrillation (AF). We hypothesized that parameters of HRV may be predictive of cardiovascular death in patients with AF. Methods and Results From the multicenter prospective Swiss-AF (Swiss Atrial Fibrillation) Cohort Study, we enrolled 1922 patients who were in sinus rhythm or AF. Resting ECG recordings of 5-minute duration were obtained at baseline. Standard parameters of HRV (HRV triangular index, SD of the normal-to-normal intervals, square root of the mean squared differences of successive normal-to-normal intervals and mean heart rate) were calculated. During follow-up, an end point committee adjudicated each cause of death. During a mean follow-up time of 2.6±1.0 years, 143 (7.4%) patients died; 92 deaths were attributable to cardiovascular reasons. In a Cox regression model including multiple covariates (age, sex, body mass index, smoking status, history of diabetes mellitus, history of hypertension, history of stroke/transient ischemic attack, history of myocardial infarction, antiarrhythmic drugs including ß blockers, oral anticoagulation), a decreased HRV index ≤ median (14.29), but not other HRV parameters, was associated with an increase in the risk of cardiovascular death (hazard ratio, 1.7; 95% CI, 1.1-2.6; P=0.01) and all-cause death (hazard ratio, 1.42; 95% CI, 1.02-1.98; P=0.04). Conclusions The HRV index measured in a single 5-minute ECG recording in a cohort of patients with AF is an independent predictor of cardiovascular mortality. HRV analysis in patients with AF might be a valuable tool for further risk stratification to guide patient management. Registration URL: https://www.clinicaltrials.gov; Unique identifier: NCT02105844.