Abstract 18295: Non-contrast Quantitative Peak-Exercise Calf Muscle Perfusion by MRI Reproducibly Discriminates Peripheral Arterial Disease from Normal
Background: Prior work demonstrated the utility of gadolinium-enhanced calf muscle perfusion measures by magnetic resonance imaging (MRI) in patients with peripheral arterial disease (PAD). Arterial spin labeling MRI (ASL) for quantification of calf muscle blood flow could provide a non-contrast alternative in patients with advanced renal disease. We hypothesized that ASL would reliably discriminate peak exercise calf muscle blood flow between normal subjects and patients with PAD.
Methods: PAD patients had symptomatic claudication, ankle brachial index (ABI) 0.4–0.9 and normal subjects (NL) had no PAD risk factors. All subjects performed supine plantar flexion exercise until exhaustion or limiting symptoms with a flexible calf coil in a Siemens 3-T MRI scanner using a pedal ergometer. At end-exercise, 15 averaged images were acquired using a pulsed ASL pulse sequence with single-shot echo-planar imaging readouts. Spin labeling was performed using the proximal inversion with control for off-resonance effects technique. Perfusion was measured by placing a region of interest in the calf muscle with the greatest signal intensity.
Results: Peak exercise calf perfusion (mean±SD) of 15 NL (age 54±9) was significantly higher than in 7 PAD (age 65±5, ABI 0.64±0.14), see Table. Five NL performed exercise matched to PAD (240s) and demonstrated higher perfusion (Table). Repeat testing on 2 different days was performed in 11 subjects (5 NL, 6 PAD) with mean group perfusion at the 2 sessions of 68±29mL/min-100g and 66±33mL/min-100g with an intra-class correlation coefficient 0.90.
Conclusion: ASL is a reproducible non-contrast technique for quantifying peak exercise blood flow in calf muscle. ASL discriminates between NL and PAD, independent of exercise time. This technique may prove to be useful for clinical trials of therapies aimed at improving muscle perfusion.
- © 2010 by American Heart Association, Inc.