Aerobic Fitness as a Predictor of Conduit, Resistance and, Microvascular Arterial Function

Abstract

Introduction Vascular dysfunction increases cardiovascular disease (CVD) risk, whereas aerobic fitness (VO2peak) improves arterial function and decreases CVD risk. However, it is unclear if VO2peak has the same degree of importance across each segment of the arterial tree (e.g., conduit, resistance, and microvasculature). This is relevant given that research has not assessed these three segments in the same cohort. Purpose To examine the relationship of VO2peak and conduit, resistance, and microvasculature arterial function. Methods Graded exercise testing assessed VO2peak in 33 males (41±19 years, 25.6±2.6 kg/m‐2, 41.1±13.6 ml/kg‐1/min‐1) and 28 females (30±12 years, 23.3±4.3 kg/m‐2, 33.6±8.5 ml/kg‐1/min‐1). Concurrent brachial artery flow‐mediated dilation (FMD) and forearm near‐infrared spectroscopy (NIRS) examined conduit, resistance, and microvascular arterial function. FMD measured with ultrasonography to continuously record arterial diameters and Doppler velocities for 1 min baseline, 5 min forearm occlusion (250 mmHg), and 3 min recovery. The maximum percent change in diameter compared with baseline defined FMD (%) and was used to evaluate conduit arterial function. Reactive hyperemia (RH) of forearm resistance arteries was calculated as peak brachial blood flow following cuff release. Forearm tissue saturation index using NIRS during FMD was used to evaluate microvasculature function (reperfusion slope and reperfusion magnitude). Multivariate regression analysis was performed using VO2peak, age, sex, and BMI as independent variables. Results Age was the only predictor of FMD (β ‐0.48 [‐0.02, ‐0.01], p=0.001), sex was the only predictor of RH, females exhibited lower RH, (β ‐0.66 [‐0.30, ‐0.15], p<0.001), and VO2peak only predicted reperfusion slope (β 0.56 [1.46, 4.52], p< 0.001) and reperfusion magnitude (β 0.36 [3.15, 41.66], p=0.02). Conclusion In our cohort, aerobic fitness was associated with microvascular function when age, BMI, and sex were included in the model. Only age was associated with conduit artery function, and only sex was associated with resistance arterial function. Each segment of the arterial tree was affected differently by VO2peak, age, and sex. These data show the importance of including several potentially important variables when investigating the association between VO2peak and arterial function.