Comparison of Indices Used to Assess Microvascular Function During Post‐Occlusion Reactive Hyperemia in Humans

Abstract

Numerous studies have used reactive hyperemia in response to cuff occlusion to assess microvascular function/reactivity. However, there are inconsistencies amongst these studies in regard to the indices used to quantify microvascular function/reactivity. Some studies do not provide accurate details of their analysis, while others report different indices such as peak velocity post occlusion or reactive hyperemic velocity area under the curve (AUC) from cuff release up to varying durations (i.e., 1 min, 2 min or back to baseline). As such, the lack of consistency in the reported indices makes it challenging to compare microvascular function between studies. Moreover, it remains unclear as to which index better characterizes microvascular function. Therefore, to elucidate the marker(s) that better detect differences in microvascular function, we compared young healthy subjects (YH) with normal vascular function (n = 10, age = 21 ± 1 yrs, BMI = 24.4 ± 0.7 kg/m2, mean ± SEM), to patients with type 2 diabetes (T2D), a population known to have impaired vascular function (n = 9, age = 58 ± 11 yrs, BMI = 38.3 ± 8.2 kg/m2). Heart rate (ECG) and brachial artery diameter and blood velocity (duplex Doppler Ultrasound) were measured continuously while subjects laid in supine position. Baseline measures were recorded for 2 min, following which a cuff placed just distal to the antecubital fossa was rapidly inflated to 220 mmHg for 5 min. Measurements were recorded for 30 s prior to and 3 min after cuff release. Microvascular function was quantified using the following indices of mean blood velocity after cuff release: peak velocity, percent change in peak velocity from baseline, and reactive hyperemic velocity AUC to: peak velocity, 10 s, 30 s, 1 min, 2 min and back to baseline. Peak velocity following cuff release was not different between groups (p = 0.70), however, baseline mean blood velocity was higher in T2D patients (T2D: 13.9 ± 1.8 cm/s vs. YH: 9.1 ± 1.7 cm/s; p = 0.04). Thus, we compared the percent change in peak velocity from baseline, which was significantly lower in T2D patients (T2D: 414.9 ± 63.5% vs. YH: 680.1 ± 107.8%; p = 0.03). AUC to peak blood velocity was also significantly lower in T2D (T2D: 289.6 ± 24.4 a.u. vs. YH: 453.73 ± 52.9 a.u.; p = 0.02); however, a shorter time to peak velocity in the T2D group likely contributed (T2D: 6.4 ± 0.8 s vs. YH: 10.2 ± 0.9 s; p = 0.007). To compare a similar duration between the groups, AUC up to 10 s, 30 s, 1 min, 2 min and back to baseline were calculated and these indices were not different between groups (e.g., AUC up to 30 s, T2D: 951.5 ± 84.9 a.u. vs. YH: 1141.0 ± 101.0; p = 0.13). Collectively, these preliminary results suggest that percent increase in peak velocity was able to discern the difference in microvascular function between the healthy and T2D groups whereas other indices were less consistent.Support or Funding InformationSupported by UTA College of Nursing and Health InnovationThis abstract is from the Experimental Biology 2019 Meeting. There is no full text article associated with this abstract published in The FASEB Journal.