Aortic pulse pressure homeostasis emerges from physiological adaptation of systemic arteries to local mechanical stresses

Abstract

Nguyen PH, Tuzun E, Quick CM. Aortic pulse pressure homeostasis emerges from physiological adaptation of systemic arteries to local mechanical stresses. Am J Physiol Regul Integr Comp Physiol 311: R522-R531, 2016. First published June 15, 2016 doi:10.1152/ajpregu.00402.2015.-Aortic pulse pressure arises from the interaction of the heart, the systemic arterial system, and peripheral microcirculations. The complex interaction between hemodynamics and arterial remodeling precludes the ability to experimentally ascribe changes in aortic pulse pressure to particular adaptive responses. Therefore, the purpose of the present work was to use a human systemic arterial system model to test the hypothesis that pulse pressure homeostasis can emerge from physiological adaptation of systemic arteries to local mechanical stresses. First, we assumed a systemic arterial system that had a realistic topology consisting of 121 arterial segments. Then the relationships of pulsatile blood pressures and flows in arterial segments were characterized by standard pulse transmission equations. Finally, each arterial segment was assumed to remodel to local stresses following three simple rules: 1) increases in endothelial shear stress increases radius, 2) increases in wall circumferential stress increases wall thickness, and 3) increases in wall circumferential stress decreases wall stiffness. Simulation of adaptation by iteratively calculating pulsatile hemodynamics, mechanical stresses, and vascular remodeling led to a general behavior in response to mechanical perturbations: initial increases in pulse pressure led to increased arterial compliances, and decreases in pulse pressure led to decreased compliances. Consequently, vascular adaptation returned pulse pressures back toward baseline conditions. This behavior manifested when modeling physiological adaptive responses to changes in cardiac output, changes in peripheral resistances, and changes in local arterial radii. The present work, thus, revealed that pulse pressure homeostasis emerges from physiological adaptation of systemic arteries to local mechanical stresses. vascular adaptation; compliance resetting; pulsatile hemodynamics; multiscale modeling AORTIC PULSE PRESSURE APPEARS to be homeostatic despite the lack of global regulatory mechanisms affecting elastic arteries. Cardiac output, peripheral resistances, and arterial compliances are the primary mechanical determinants of aortic pressures (40,47). Whereas mean pressure is predominantly determined by cardiac output and peripheral resistance, pulse pressure (systolic-diastolic) is also affected by compliance (the change in volume per change in transmural pressure) of the large elastic arteries (69). As arterial compliances decrease, pulse pressures tend to increase (40,41,47,48). Acutely, mean pressure and pulse pressure are physiologically coupled by feedback mechanisms: when pulse pressure rises, stretch-sensitive baroreceptors lower peripheral resistance, i.e., the baroreflex, which, in turn, lowers mean pressure. Furthe...

Mechanisms of the Osteogenic Switch of Smooth Muscle Cells in Vascular Calcification: WNT Signaling, BMPs, Mechanotransduction, and EndMT

“…Under typical conditions, blood pressure stimulates homeostatic responses. However, under hypertension, pressure could potentially induce an excessive mechanical response, exacerbating vascular injury [74][75][76][77]. A combination of both pathologies may overstimulate remodeling responses, and in the case of calcification, promote the growth of the present mineralized matrix.…”