Detection of peripheral vascular stenosis by assessing skeletal muscle flow reserve

Objectives: We sought to determine whether the severity of peripheral arterial disease (PAD) can be assessed by measuring blood flow reserve in limb skeletal muscle with contrast-enhanced ultrasound (CEU). Background: Noninvasive imaging of distal limb perfusion could improve management of patients with PAD by evaluating the impact of large and small vessel disease, and collateral flow. Methods: In 12 dogs, blood flow in the quadriceps femoris was measured by CEU at rest and during either electrostimulated contractile exercise or adenosine infusion. Femoral artery blood flow was measured by Doppler ultrasound. Studies were performed in the absence and presence of either moderate or severe stenosis (pressure gradient of 10 to 20 mm Hg and >20 mm Hg, respectively). Results: Resting femoral artery blood flow progressively decreased with stenosis severity, while resting skeletal muscle flow was reduced only with severe stenosis (52 ± 21% of baseline, p < 0.05), indicating the presence of collateral flow. Skeletal muscle flow reserve during contractile exercise or adenosine decreased incrementally with increasing stenosis severity (p < 0.01). The stenotic pressure gradient correlated with skeletal muscle flow reserve for exercise and adenosine (r = 0.70 for both, p < 0.01). Conclusions: Contrast-enhanced ultrasound of limb skeletal muscle can be used to assess the severity of PAD by measuring muscle flow reserve during either contractile exercise or pharmacologic vasodilation. Unlike currently used methods, this technique may provide a measure of the physiologic effects of large- and small-vessel PAD, and the influence of collateral perfusion.