Abstract 13174: MR-based Calf Muscle Perfusion Index Correlates with Treadmill Exercise Test Parameters in Patients with Peripheral Arterial Diseases
Introduction: Current methods designed to assess the efficacy of therapeutic interventions in patients with peripheral arterial disease (PAD) are limited by variability and changes representing the placebo effect. Gadolinium-enhanced first-pass (FP) MRI is an emerging method to assess perfusion in calf muscle at peak exercise. Hypothesis: We hypothesized that calf muscle perfusion index measured with FP MRI at peak exercise correlates with treadmill exercise measures of ischemia in patients with PAD.
Methods: In 70 patients with PAD, images were acquired at peak exercise on a 1.5T MRI using a dynamic, first-pass, dual-contrast sequence. Patients exercised until fatigue using an MR-compatible plantar-flexion ergometer. The MRI sequence acquires two interleaved slices; an inversion-prepared slice in the calf muscle, and a saturation-prepared slice in the popliteal artery (8 cm superior). Time-intensity curves (TIC) were acquired from the dynamic images by placing ROI’s in the popliteal artery on the saturation-prepared slices in the brightest calf muscle group on the inversion-prepared slice (Figure 1). The perfusion index (PI) = calf muscle TIC upslope / popliteal artery TIC upslope. Graded treadmill exercise testing was performed using the Gardner protocol. Claudication onset time (COT) and total walking time (TWT) were recorded for each patient, as well as resting ABI.
Results: 53 patients were able to complete both the MRI and treadmill test. MRI PI correlated with the exercise measures COT and the TWT (r=0.44 p<0.001, r=0.40 p=0.001, respectively). MRI PI was not correlated with resting ABI.
Conclusion: MR-based calf muscle PI correlates with treadmill exercise parameters. MRI PI could be a valuable tool to objectively and quantitatively assess improvement in exercise perfusion in response to therapeutic intervention in patients with PAD.
- © 2012 by American Heart Association, Inc.