Abstract 12974: Peak Calf Muscle Perfusion is Similar With Post-Occlusion Hyperemia and Exercise in PAD
Objective: Pulsed arterial spin labeling (PASL) is a non-contrast magnetic resonance imaging (MRI) technique that can be used to quantify calf muscle perfusion with stress. We hypothesized that post-occlusion hyperemia would yield greater flow compared to exercise in peripheral artery disease (PAD) and healthy subjects when measured by PASL.
Methods: Twenty PAD patients (45% M) and 24 healthy subjects (50% M) were enrolled. Exercise was plantar flexion pedal ergometry to exhaustion. Occlusion was achieved by inflation of a thigh cuff to 200 mmHg for 5 minutes. Fifteen averaged PASL images were acquired using a single-shot echo-planar pulse sequence at peak exercise [14 healthy (Nl-Ex); 15 PAD (PAD-Ex)] or immediately after cuff deflation [10 healthy (Nl-Cuff), 5 PAD (PAD-Cuff)]. Regions of interest were drawn in each calf muscle group. The highest muscle flow was measured for exercise, while an average of all muscle groups was used for reactive hyperemia.
Results: Healthy subjects were younger than PAD (53 ± 8 vs. 65 ± 9, p ≤ 0.001). Ankle-brachial index was similar between PAD groups (0.72 ± 0.12 vs. 0.68 ± 0.03, p = 0.54). Nl-Ex subjects exercised longer than PAD patients (631 ± 388 s vs. 218 ± 105 s, p ≤ 0.005). Perfusion was higher in Nl-Cuff than Nl-Ex (121 ± 35 vs. 78 ± 23 mL/min-100g, p ≤ 0.001), but similar in PAD-Cuff and PAD-Ex (45 ± 27 vs. 42 ± 15 mL/min-100g, p = 0.841) (Fig 1 - left, *p≤0.05 vs. Nl-Ex, ^ p=NS vs. PAD-Ex). Flow in both Nl groups was higher than PAD patients. Exercise yielded increased flow in the muscles utilized in both groups, whereas reactive hyperemia yielded a homogenous flow pattern in normal subjects (Fig 1 - right). In PAD patients, however, the flow increase was seen primarily in the soleus.
Conclusions: In contrast to healthy subjects, cuff occlusion hyperemia in PAD yields peak flow similar to exercise when measured with PASL MRI. The lack of homogenous reactive hyperemia in PAD patients may be indicative of microvascular disease.
- Magnetic resonance imaging
- Peripheral arterial disease
- Perfusion imaging
- Muscle, skeletal
- Exercise tests
- © 2013 by American Heart Association, Inc.