Arterial spin labeling perfusion cardiovascular magnetic resonance of the calf in peripheral arterial disease: Cuff occlusion hyperemia vs exercise

Background: Assessment of calf muscle perfusion requires a physiological challenge. Exercise and cuff-occlusion hyperemia are commonly used methods, but it has been unclear if one is superior to the other. We hypothesized that post-occlusion calf muscle perfusion (Cuff) with pulsed arterial spin labeling (PASL) cardiovascular magnetic resonance (CMR) at 3 Tesla (T) would yield greater perfusion and improved reproducibility compared to exercise hyperemia in studies of peripheral arterial disease (PAD). Methods: Exercise and Cuff cohorts were independently recruited. PAD patients had an ankle brachial index (ABI) between 0.4-0.9. Controls (NL) had no risk factors and ABI 0.9-1.4. Subjects exercised until exhaustion (15 NL-Ex, 15 PAD-Ex) or had a thigh cuff inflated for 5 minutes (12 NL-Cuff, 11 PAD-Cuff). Peak exercise and average cuff (Cuff_mean) perfusion were compared. Six participants underwent both cuff and exercise testing. Reproducibility was tested in 8 Cuff subjects (5 NL, 3 PAD). Results: Controls had greater perfusion than PAD independent of stressor (NL-Ex 74 ± 21 vs. PAD-Ex 43 ± 10, p = 0.01; NL-Cuff_mean 109 ± 39 vs. PAD-Cuff_mean 34 ± 17 ml/min-100 g, p < 0.001). However, there was no difference between exercise and Cuff_mean perfusion within groups (p > 0.6). Results were similar when the same subjects had the 2 stressors performed. Cuff_mean had superior reproducibility (Cuff_mean ICC 0.98 vs. Exercise ICC 0.87) and area under the receiver operating characteristic curve (Cuff_mean 0.992 vs. Exercise 0.905). Conclusions: Cuff hyperemia differentiates PAD patients from controls, as does exercise stress. Cuff_mean and exercise calf perfusion values are similar. Cuff occlusion hyperemia has superior reproducibility and thus may be the preferred stressor.