Comparison Of Whole-forearm And Skin Post-occlusive Reactive Hyperemia As Indices Of Microvascular Function

Abstract

BACKGROUND: Post-occlusive reactive hyperemia (PORH) is often used as a test of microvascular function. However, the method of PORH measurement and the reporting of PORH values varies widely between studies, from measurements on the skin or whole-forearm to reporting peak or cumulative PORH values. As such, the optimal measurement and reporting of PORH values remains unclear. PURPOSE: To compare whole-forearm and skin PORH between older adults with conditions typically associated with microvascular dysfunction (type 2 diabetes, T2D), macrovascular dysfunction (non-diabetic coronary artery disease, CAD) and healthy controls (CTRL). METHODS: We retrospectively analyzed data obtained from 13 T2D patients (61 ± 9 years, 6 M ; 7 W), 21 CAD patients (65 ± 9 years, 18 M ; 3 W) and 13 CTRL (65 ± 7 years, 9 M ; 4 W). Forearm vascular conductance (FVC, duplex ultrasound) and cutaneous vascular conductance (CVC, laser-Doppler) were measured simultaneously before and for 3 minutes after 5 minutes of forearm ischemia. PORH was quantified as: absolute peak (Peak), change from baseline to peak (∆) and area under the curve above baseline (AUC). RESULTS: Baseline FVC (P=0.84) and CVC (P=0.31) were similar between groups. Peak FVC was similar between groups (P=0.24), while ∆FVC tended to be reduced in T2D compared to CAD (P=0.06) and CTRL (P=0.07). FVC AUC was reduced in T2D compared to CTRL (P=0.03), while values in CAD did not differ from T2D or CTRL. Peak CVC (T2D: P=0.04, CAD: P=0.02) and ∆CVC (T2D: P=0.03, CAD: P=0.01) were reduced in T2D and CAD. There was a trend for CVC AUC to differ between groups (P=0.06). The different indices of PORH for a given measurement (forearm vs skin) were strongly correlated (r=0.755 to 0.906 between FVC descriptors, r=0.768 to 0.991 between CVC descriptors, all P<0.001). However, FVC indices of PORH weakly correlated with CVC indices (r=0.237 to 0.374, P=0.01 to 0.11). CONCLUSIONS: Whole-forearm and skin PORH provide different information on microvascular function in older adults. A decreased PORH in the whole-forearm appears to be a feature of T2D and not CAD, while a decreased PORH in forearm skin seems to be detectable in both T2D and CAD.