Differences in heart rate responses to upright posture are associated with variations in the high-frequency power of heart rate variability

Am J Physiol Heart Circ Physiol. 2023 Dec 22. doi: 10.1152/ajpheart.00567.2023. Online ahead of print.ABSTRACTHigh resting heart rate is a cardiovascular risk factor, but limited data exists on the underlying hemodynamics and reproducibility of supine-to-upright increase in heart rate. We recorded non-invasive hemodynamics in 574 volunteers (age 44.9 years, BMI 26.4 kg/m2, 49% male) during passive head-up tilt (HUT) using whole-body impedance cardiography and radial artery tonometry. Heart rate regulation was evaluated using heart rate variability (HRV) analyses. Comparisons were made between quartiles of supine-to-upright heart rate changes, in which heart rate at rest ranged 62.6-64.8 beats/min (p=0.285). The average upright increases in heart rate in the quartiles 1‑4 were 4.7, 9.9, 13.5, and 21.0 beats/min, respectively (p<0.0001). No differences were observed in low frequency power of HRV whether supine or upright, or supine high frequency power of HRV. Upright high frequency power of HRV was highest in quartile 1 with lowest upright heart rate, and lowest in quartile 4 with highest upright heart rate. Mean systolic blood pressure before and during HUT (126 vs. 108 mmHg), and the increase in systemic vascular resistance during HUT (650 vs. 173 dyn×s/cm5×m2), were highest in quartile 1 and lowest in quartile 4. The increases in heart rate during HUT on three separate occasions several weeks apart were highly reproducible (r=0.682) among 215 participants. To conclud...
Source: American Journal of Physiology. Heart and Circulatory Physiology - Category: Physiology Authors: Source Type: research