目的:心血管(CV)系统在温度调节中起着至关重要的作用,因为它通过血液分布的变化通过强制对流和传导对传热产生影响,血流速度,以及血管与周围组织的接近度。要充分了解心血管系统在体温调节中的作用,血液分布(受心输出量的影响,血管尺寸,血流量,和压力)必须量化,理想的性别和年龄。此外,壁切应力是量化的,因为它是心血管疾病定位和进展的重要指标。通过调查热条件对壁剪应力的影响在一个健康的基线,研究人员可以开始研究热条件与病理或运动的汇合。这项研究的目的是确定性别和年龄对CV对温度响应的影响。在这项工作中,核心体温对小鼠动脉和静脉系统的血流动力学的影响已被非侵入性研究,在不同年龄和性别的多个地点。
方法:男性和女性,成人和老年人,将小鼠(n=20)麻醉并在7T时接受MRI检查。数据来自四个共同定位的血管对(颈部[颈动脉/颈静脉],躯干[肾上和肾下主动脉/下腔静脉(IVC)],外周[股动脉/静脉])在35、36、37和38°C的核心温度下。十六岁东北,心电图门控,具有单向速度编码(通过平面)的相衬帧被获取为垂直于每个血管。使用半自动内部MATLAB脚本分析每个帧以量化血流速度和体积流量。使用Hagen-Poiseulle公式计算壁剪切应力(WSS)。股动脉WSS的多变量回归与温度拟合,性别,年龄,体重,和心率作为变量。
结果:在四个核心体温下对八个血管中的血流速度和体积流量进行定量。所有组的肾下IVC流量随温度线性增加(p=0.002;调整后的斜率:男性与女性,0.37和0.28厘米/(s×℃);成人与年龄,0.22和0.43cm/(s×℃))。比较平均体积流量对温度的响应,肾上主动脉组不同(成人<老年人,p<.05),股动脉(成人<老年人,p<.05),和股静脉(成年男性<老年男性,p<.001)。温度和体重以及温度和性别的双向交互作用对壁剪应力的影响最大。
结论:年龄,特别是,对通过体积流量测量的血液动力学反应有显著影响(例如,老年男性>成年男性)和收缩期峰值时的WSS(例如,老年男性<成年男性)。血液动力学数据可以提供生理相关参数,包括性别和年龄差异,计算流体动力学模型,并提供健康小鼠脉管系统的基线数据,以用作研究心血管系统的各种生理(热应力)和病理生理状况的基准。
OBJECTIVE: The cardiovascular (CV) system plays a vital role in thermoregulation because of its influence on heat transfer via 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: Male and female, adult and aged, mice (n = 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.
RESULTS: Blood velocity and volumetric flow were quantified in eight vessels at four core body temperatures. Flow in the infrarenal IVC linearly increased with temperature for all groups (p = .002; adjusted means of slopes: male vs. female, 0.37 and 0.28 cm/(s × °C); adult vs. aged, 0.22 and 0.43 cm/(s × °C)). Comparing average volumetric flow response to temperature, groups differed for the suprarenal aorta (adult < aged, p < .05), femoral artery (adult < aged, p < .05), and femoral vein (adult male < aged male, p < .001). 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.