Noninvasive assessment of temporal dynamics in sympathetic and parasympathetic baroreflex responses

<i>Objective.</i>The baroreflex maintains cardiovascular stability by modulating heart rate, myocardial contraction, and vascular tone. However, noninvasive assessment of its sympathetic vascular and myocardial branches often overlooks their time-dependent interplay. To address this gap, we developed and implemented a noninvasive method that characterizes these baroreflex dynamics to enhance understanding of autonomic function and improve clinical assessments of cardiovascular regulation.<i>Approach.</i>We analyzed blood pressure and ECG recordings from 55 preoperative patients and 21 participants from the EUROBAVAR dataset. Baroreflex sensitivity (BRS) was calculated using the sequence method for interbeat interval (IBI), myocardial contractility (d<i>P</i>/d<i>t</i>_max), and systemic vascular resistance (SVR), derived through pulse contour analysis at multiple delays relative to beat-to-beat changes in systolic arterial pressure (SAP). Correlations of these BRS estimates with hemodynamic parameters and heart rate variability (HRV) were evaluated at rest and during active standing.<i>Main results.</i>Distinct temporal profiles of BRS for IBI, SVR, and d<i>P</i>/d<i>t</i>_maxwere identified, with significant correlations to HRV and average SVR, CO, and SAP levels at physiologically relevant delays. Orthostatic stress primarily impacted parasympathetic BRS for IBI, while BRS for SVR and d<i>P</i>/d<i>t</i>_maxshowed subtler changes, reflecting unique time-dependent associations.<i>Significance.</i>This approach provides a tool to comprehensively understand the baroreflex function, highlighting the latency-dependent interactions of its branches with their effectors and their adaptability to physiological challenges. Such insights could improve clinical assessments of autonomic dysfunction with altered baroreflex latencies and inform personalized strategies for managing conditions that compromise cardiovascular stability.