An exercise stress test for contrast-enhanced duplex ultrasound assessment of lower limb muscle perfusion in patients with peripheral arterial disease

The aim of the present study was to develop a standardized contrast-enhanced duplex ultrasound (CE-DUS) protocol to assess lower-extremity muscle perfusion before and after exercise and determine relationships of perfusion with clinical and functional measures. CE-DUS (EPIQ 5G, Philips) was used before and immediately after a 10-minute, standardized bout of treadmill walking to compare microvascular perfusion of the gastrocnemius muscle in older (55-82 years) peripheral arterial disease (PAD) patients (n=15, mean ± SEM ABI=0.78±0.04) and controls (n=13). Microvascular blood volume (MBV) and microvascular flow velocity (MFV) were measured at rest and immediately following treadmill exercise, and the Modified Physical Performance Test (MPPT) was used to assess mobility function. In the resting state (pre-exercise) MBV in PAD patients was not significantly different than normal controls (5.17±0.71 vs. 6.20±0.83 arbitrary units (AU) respectively; P=0.36); however, after exercise, MBV was ∼40% lower in PAD patients compared with normal controls (5.85±1.13 vs. 9.53±1.31 AU respectively; P=0.04). Conversely, MFV was ∼60% higher in PAD patients compared with normal controls after exercise (0.180±0.016 vs. 0.113±0.018 AU respectively; P=0.01). There was a significant between-group difference in the exercise-induced changes in both MBV and MFV (P≤0.05). Both basal and exercise MBV directly correlated with MPPT score in the PAD patients (r=0.56-0.62, P