Maximal Calf Vasodilation Influences 6-Minute Walk Distance In PAD And Non-PAD Groups

Abstract

PURPOSE: To (1) compare the maximal calf vascular conductance and 6-minute walk distance (6MWD) of participants with and without symptomatic peripheral artery disease (PAD), and (2) determine whether maximal calf vascular conductance was associated with 6MWD in both groups before and after adjusting for ankle-brachial index (ABI), and for demographic, anthropometric, and co-morbid characteristics. METHODS: Participants with (n = 633, 67.7 + 8.4 yr) and without (n = 327, 63.9 ± 10.4 yr) PAD underwent ambulatory function testing including 6MWD, resting ABI, and plethysmographic measurements of calf blood flow and vascular conductance at rest and during maximal hyperemia (ischemic toe raises to fatigue). Participants were further characterized on demographic, anthropometric, and co-morbid (age, hypertension, diabetes, smoking, etc) variables. RESULTS: The PAD group had lower maximal calf conductance (135.8 ± 71.4 vs. 200.7 ± 112.7 % reperfusion/min/mmHg, p < 0.001) and shorter 6MWD (375 ± 98 vs. 480 ± 107 meters, p < 0.001) than the non-PAD group (means+SD). Maximal calf conductance was positively associated with 6MWD in the PAD group (p < 0.001) and in the non-PAD group (p < 0.001). These positive associations remained significant after adjusting for disease severity (ABI) and co-morbid conditions in the PAD group (p < 0.001), and after adjusting for age and co-morbid conditions in the non-PAD group (p < 0.001). Calf circumference was also a significant independent predictor of 6MWD in both groups (p < 0.001) CONCLUSIONS: Maximal calf vascular conductance, an index of microvascular function, is important in explaining variance in 6MWD in PAD and non-PAD groups, even after controlling for ABI and the influences of co-morbid conditions.