Dynamic characteristics of T2*-weighted signal in calf muscles of peripheral artery disease during low-intensity exercise

Purpose: To evaluate the dynamic characteristics of T^*₂-weighted signal change in exercising skeletal muscle of healthy subjects and peripheral artery disease (PAD) patients under a low-intensity exercise paradigm. Materials and Methods: Nine PAD patients and nine age- and sex-matched healthy volunteers underwent a low-intensity exercise paradigm while magnetic resonance imaging (MRI) (3.0T) was obtained. T^*₂-weighted signal time-courses in lateral gastrocnemius, medial gastrocnemius, soleus, and tibialis anterior were acquired and analyzed. Correlations were performed between dynamic T^*₂ -weighted signal and changes in heart rate, mean arterial pressure, leg pain, and perceived exertion. Results: A significant signal decrease was observed during exercise in soleus and tibialis anterior of healthy participants (P = 0.0007–0.04 and 0.001–0.009, respectively). In PAD, negative signals were observed (P = 0.008–0.02 and 0.003–0.01, respectively) in soleus and lateral gastrocnemius during the early exercise stage. Then the signal gradually increased above the baseline in the lateral gastrocnemius during and after exercise in six of the eight patients who completed the study. This signal increase in patients' lateral gastrocnemius was significantly greater than in healthy subjects' during the later exercise stage (two-sample t-tests, P = 0.001–0.03). Heart rate and mean arterial pressure responses to exercise were significantly higher in PAD than healthy subjects (P = 0.036 and 0.008, respectively) and the patients experienced greater leg pain and exertion (P = 0.006 and P = 0.0014, respectively). Conclusion: During low-intensity exercise, there were different dynamic T^*₂-weighted signal behavior in the healthy and PAD exercising muscles. Level of Evidence: 2. Technical Efficacy: Stage 1. J. MAGN. RESON. IMAGING 2017;46:40–48.