Resting skin sympathetic nerve activity spectral characteristics are associated with orthostatic sympathetic responses and exaggerated orthostatic pressor response in hypertension.

Abstract

Substantial interindividual variability exists in orthostatic sympathetic and blood pressure (BP) responses among patients with hypertension. We investigated whether resting skin sympathetic nerve activity (SKNA) spectral characteristics are associated with this variability and with exaggerated orthostatic pressor responses (EPR). In 108 patients with hypertension, BP and SKNA were recorded in the supine and active standing positions. SKNA amplitude (average SKNA [aSKNA]) and frequency-domain parameters (low-frequency [LF] and high-frequency [HF] components, LF/HF ratio) were analyzed. Patients were stratified into low-LF/HF and high-LF/HF groups based on the median supine SKNA-derived LF/HF ratio. EPR was defined as a systolic BP increase of ≥ 20 mmHg at 3 min of active standing. Active standing significantly increased aSKNA (P < 0.001), whereas the overall SKNA-derived LF/HF ratio showed no significant change (P = 0.081). Upon standing, the low-LF/HF group exhibited a significant increase in LF/HF (P = 0.004), whereas the high-LF/HF group exhibited a decrease (P < 0.001), with an attenuation of the between-group difference during standing (P = 0.162). EPR occurred exclusively in the low-LF/HF group (13.0% vs. 0%, P = 0.013). In a receiver operating characteristic analysis, the supine LF/HF ratio discriminated EPR with an area under the curve of 0.863 (95% confidence interval, 0.775-0.950). Resting SKNA spectral characteristics may characterize interindividual variability in orthostatic sympathetic responses and be associated with EPR, offering a non-invasive approach for sympathetic phenotyping in hypertension In patients with hypertension, the supine SKNA-derived LF/HF ratio was inversely associated with its orthostatic change. LF/HF ratio increased during standing in the low-LF/HF group but decreased in the high-LF/HF group, with smaller group difference during standing. The supine LF/HF ratio showed potential for discriminating exaggerated orthostatic pressor responses.