Dissection of long-range heart rate variability: Controlled induction of prognostic measures by activity in the laboratory

Abstract Objectives We sought to determine whether the long-range measures of heart rate variability (HRV)—the standard deviation of sequential 5-min heart period mean values (SDANN) and the heart period spectral amplitude in the ultra-low frequency band Background The SDANN and ULF are prognostic HRV factors whose physiologic origins are obscure. Their discontinuous presence throughout the day suggested that they arise from changes in heart period due to activity. Methods Heart period sequences were recorded from 14 patients with left ventricular dysfunction and 14 control subjects during an unrestricted 24-h day, 4-h supine rest, and 4-h epoch with scripted activities. Results The SDANN was higher during activity than during rest (74 ± 23 ms vs. 43 ± 17 ms, p Conclusions Activity increases SDANN by increasing the range of heart periods. Patients with diminished ventricular function have a reduced SDANN on ambulatory electrocardiograms, possibly and partly because of a higher mean heart rate and reduced variations in physical activity.