Preliminary Heart Rate Variability Values in Minoritized Older Surgery Patients

Abstract

Background: This study aims to characterize heart rate variability (HRV) in older adults from different racial backgrounds awaiting major surgery, with a focus on how chronic stress affects autonomic regulation. We hypothesize that autonomic fractionation, a paradoxical combination of high HRV and elevated blood pressure (BP), will be more prevalent among older Black/African Americans (B/AA) compared to age-, sex-, and surgery-matched White/Caucasian Americans (W/CA), even after adjusting for key demographic and clinical variables. While high HRV typically indicates physiological resilience, its coexistence with high hemodynamic metrics may reflect maladaptive autonomic regulation, potentially. Methods: We assessed HRV using 24-hour recordings from eCardioWatch 287 wristbands in race- and procedure-matched geriatric surgical patients. Overnight segments were analyzed to reduce motion artifacts. Time-domain (SDRR, RMSSD) and frequency-domain (LF, HF, LF/HF ratio) HRV metrics were extracted using Kubios, MATLAB, and Python, alongside hemodynamic measures including pulse pressure (PP), systolic and diastolic blood pressure (SBP, DBP), and mean arterial pressure (MAP). Paired t-tests were used to compare autonomic and vascular indicators between B/AA and WCA patients. Results: B/AA patients exhibited paradoxically elevated but highly variable HRV measures. SDRR was nearly double in B/AA patients compared to WCA (40.29 ms ± 29.36% vs. 21.95 ms ± 9.53%, p = 0.124), with a similar trend in RMSSD (50.37 ms ± 42.63% vs. 22.29 ms ± 8.78%, p = 0.092). Despite statistical non-significance, these differences suggest autonomic instability. Hemodynamic profiles showed wider pulse pressures in B/AA patients (64.50 mmHg ± 18.52% vs. 54.50 mmHg ± 12.64%, p = 0.114) and significantly lower DBP (69.90 mmHg ± 10.28% vs. 78.50 mmHg ± 8.00%, p = 0.029), indicating vascular stiffening. Frequency domain analysis revealed a lower LF/HF ratio in B/AA patients (0.789 ± 0.383%) compared to CA controls (1.653 ± 1.387%, p = 0.081), contradicting expectations of sympathetic dominance. Discussion: This study reveals a paradoxical autonomic profile in older B/AA patients, characterized by significantly elevated but highly variable HRV measures, including SDRR and RMSSD, compared to matched WCA controls. While group differences did not always reach statistical significance, the large effect sizes and pronounced interindividual variability suggest autonomic instability rather than enhanced cardiovascular health. Hemodynamic analyses further demonstrated wider pulse pressures and significantly lower diastolic blood pressure in B/AA patients, consistent with increased arterial stiffness and reduced vascular compliance. Frequency domain analysis revealed a markedly lower LF/HF ratio in B/AA patients, challenging conventional assumptions of sympathetic predominance in high-risk populations and pointing to potential baroreflex impairment or race-specific autonomic regulation.