Abstract
The cardiovagal branch of the baroreflex is of high clinical relevance when detecting disturbances of the autonomic nervous system. The hysteresis of the baroreflex is assessed using provoked and spontaneous changes in blood pressure. We propose a novel ellipse analysis to characterize hysteresis of the spontaneous respiration-related cardiovagal baroreflex for orthostatic test. Up and down sequences of pressure changes as well as the working point of baroreflex are considered. The EuroBaVar data set for supine and standing was employed to extract heartbeat intervals and blood pressure values. The latter values formed polygons into which a bivariate normal distribution was fitted with its properties determining proposed ellipses of baroreflex. More than 80% of ellipses are formed out of nonoverlapping and delayed up and down sequences highlighting baroreflex hysteresis. In the supine position, the ellipses are more elongated (by about 46%) and steeper (by about 4.3° as median) than standing, indicating larger heart interval variability (70.7 versus 47.9 ms) and smaller blood pressure variability (5.8 versus 8.9 mmHg) in supine. The ellipses show a higher baroreflex sensitivity for supine (15.7 ms/mmHg as median) than standing (7 ms/mmHg). The center of the ellipse moves from supine to standing, which describes the overall sigmoid shape of the baroreflex with the moving working point. In contrast to regression analysis, the proposed method considers gain and set-point changes during respiration, offers instructive insights into the resulting hysteresis of the spontaneous cardiovagal baroreflex with respiration as stimuli, and provides a new tool for its future analysis.
Highlights
Blood pressure in humans is governed by the arterial and cardiopulmonary baroreflex, an essential part of the autonomic nervous system
We propose a novel approach using sophisticated ellipse analysis to characterize cardiovagal baroreflex hysteresis on two levels: (i) cardiovagal hysteresis due to the respirationrelated spontaneous pressure change, and (ii) cardiovagal hysteresis due to the static pressure change in the course of the orthostatic test
This study was performed on the EuroBaVar data set1, provided by the Working Group on Blood Pressure and Heart Rate Variability of the European Society of Hypertension
Summary
Blood pressure in humans is governed by the arterial and cardiopulmonary baroreflex, an essential part of the autonomic nervous system. Changes in pressure, e.g., spontaneous due to breathing or artificial due to vasoactive drug administration, act as stimuli on baroreceptors. Sequences of pressure values and the associated heart rate values due to efferent vagal activity to the sinoatrial node form the cardiovagal. Spontaneous Cardiovagal Baroreflex Hysteresis baroreflex hysteresis loop (deBoer et al, 1987; Bertinieri et al, 1988; Parati et al, 1988; Turjanmaa et al, 1990; Saul et al, 1991). A linear regression over the linear portion of the sigmoidal function between systolic pressure and heart rate values determines the cardiovagal baroreflex gain, known as baroreflex sensitivity (BRS; deBoer et al, 1987; Parati et al, 1988; Turjanmaa et al, 1990). A reduced BRS value BRS is usually associated with cardiovascular failure (La Rovere et al, 2008), orthostatic intolerance (Cooper and Hainsworth, 2002), neurally mediated syncope (Benarroch, 2008), and amplified pain perception (Suarez-Roca et al, 2019)
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