Markers of autonomic tone on a standard ECG are predictive of mortality in old age

Background To investigate markers of autonomic tone on a standard electrocardiogram in relation to mortality in old age. Methods A total of 599 inhabitants of Leiden, the Netherlands, were enrolled in a population-based follow-up study at their 85th birthday. Electrocardiograms (ECGs) were taken on entry and annually thereafter. ECGs were analysed automatically to determine four markers of autonomic tone, i.e. heart rate, the occurrence of ventricular extrasystoles and two time domain measures of heart rate variability. All participants were followed up for mortality. Results Participants with a heart rate in the highest quartile had a 1.8-fold increased total mortality risk (95% confidence interval (CI) 1.0–3.4), but not an increased cardiovascular mortality risk. The occurrence of at least one ventricular extrasystole was related with a 2.3-fold increased total mortality risk (95% CI 1.3–3.9) and a 3.6-fold increased cardiovascular mortality (95% CI 1.6–8.2). In stratified analyses, the prognostic effect was confined to males. Both measures of heart rate variability were not related to mortality. Conclusion High heart rate and the occurrence of a ventricular extrasystole, both markers of sympathetic dominance, were predictive of mortality in old age. Two short-term measures of heart rate variability as measured on a standard 10-s ECG were not related to mortality, and hence may not reflect autonomic tone in old age.