Abstract 2152: Assessment of Peripheral Artery Disease by Imaging Limb Perfusion Reserve with Contrast Enhanced Ultrasound
Background. Current diagnostic methods for the assessment of PAD are limited due to their inability to evaluate microvascular disease and collateral flow. Because of its ability to quantitatively assess microvascular flow, we hypothesized that rest-stress limb perfusion imaging with contrast-enhanced ultrasound (CEU) could accurately assess the severity of PAD.
Methods. We studied 39 patients with PAD, (19 with diabetes mellitus [DM]), and 26 control subjects. A modified 20 min symptom-limited exercise study was performed to determine claudication threshold for each limb. Rest and post-exercise ankle-brachial index (ABI) and plythysmography pulse volume recordings (PVR) were performed for each limb. CEU of bilateral calf extensor muscles was performed at rest and during 4 min low-level calibrated plantar flexion exercise. Muscle blood flow (MBF) was determined from pulsing interval versus intensity data.
Results. During exercise, claudication occurred in all PAD patients (median time 3.9 and 1.2 min for PAD and PAD+DM patients, respectively) and in none of the controls. Rest ABI was abnormal (<0.92) in only 60% of PAD and 47% of PAD+DM patients. MBF at rest was not significantly different between the groups (2.6±2.2, 2.2±2.0, and 1.3±0.6 for controls, PAD, and PAD+DM, respectively). MBF during exercise was higher (p<0.05) for controls (20.2±9.4) than for PAD (10.2±7.0) or PAD+DM (9.2±6.8) patients. Claudication threshold correlated with exercise MBF (p<0.01) but not with ABI (rest or exercise). On multivariate analysis, both exercise MBF and MBF reserve were independent predictors for the diagnosis of PAD and for assessing severity of sympotms. The best 2 Wald test models for predicting severity of disease was DM+MBF reserve, and DM+exercise MBF. Although ABI and PVR were univariate predictors of the presence of PAD, they added no predictive value for severity of disease.
Conclusions. CEU can rapidly measure perfusion reserve in limb skeletal muscle and is superior for evaluating the severity of PAD, particularly in patients with DM, than conventional non-invasive methods that rely on measuring large vessel pressure gradients or pulse volumes.