Key result
Thermal stress, age, and sex significantly influenced hemodynamic responses such as volumetric flow and wall shear stress in a murine model (P < 0.001).
Why the study?
To fully understand thermoregulation, blood distribution and wall shear stress must be quantified across sex and age to determine their influence on the cardiovascular response to temperature.
Does core body temperature affect hemodynamics in mice across different ages and sexes?
Does core body temperature affect hemodynamics in mice across different ages and sexes?
Hemodynamic responses to thermal stress in mice vary significantly by age and sex, providing baseline data for computational fluid dynamics models.
Murine thermal hemodynamic responses vary by age and sex; hypothesis-generating for CFD models but leaves open human translation.
PURPOSE: forced convection and conduction by changes in blood distribution, blood velocity, and proximity of vessels to surrounding tissues. To fully understand the cardiovascular system's role in thermoregulation, blood distribution (influenced by cardiac output, vessel size, blood flow, and pressure) must be quantified, ideally across sex and age. Additionally, wall shear stress is quantified because it is an important metric in cardiovascular disease localization and progression. By investigating the effect of thermal conditions on wall shear stress at a healthy baseline, researchers can begin to study the confluence of thermal condition with pathology or exercise. The purpose of this study is to determine the influence of sex and age on the CV response to temperature. In this work, the effect of core body temperature on hemodynamics of the murine arterial and venous systems has been studied non-invasively, at multiple locations across age and sex. METHODS: = 20) were anesthetized and underwent MRI at 7 T. Data were acquired from four co-localized vessel pairs (the neck [carotid/jugular], torso [suprarenal and infrarenal aorta/inferior vena cava (IVC)], periphery [femoral artery/vein]) at core temperatures of 35, 36, 37, and 38 °C. Sixteen CINE, ECG-gated, phase contrast frames with one-directional velocity encoding (through plane) were acquired perpendicular to each vessel. Each frame was analyzed to quantify blood velocity and volumetric flow using a semi-automated in-house MATLAB script. Wall shear stress (WSS) was calculated using the Hagen-Poiseulle formula. A multivariable regression for WSS in the femoral artery was fitted with temperature, sex, age, body weight, and heart rate as variables. The two-way interaction terms of temperature and body weight and temperature and sex had the largest effect on wall shear stress. CONCLUSIONS: Age, in particular, had a significant impact on hemodynamic response as measured by volumetric flow (e.g., aged males > adult males) and WSS at peak-systole (e.g., aged males < adult males). The hemodynamic data can provide physiologically-relevant parameters, including sex and age difference, to computational fluid dynamics models and provide baseline data for the healthy murine vasculature to use as a benchmark for investigations of a variety of physiological (thermal stress) and pathophysiological conditions of the cardiovascular system.
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Crouch et al. (2021) studied Healthy murine vasculature (n=20). Thermal stress (core body temperatures of 35, 36, 37, and 38 °C) was evaluated on Wall shear stress and volumetric flow (p=< .001). Thermal stress, age, and sex significantly influenced hemodynamic responses such as volumetric flow and wall shear stress in a murine model (P < 0.001).
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