Diffusion tensor imaging indices of acute muscle damage are augmented after exercise in peripheral arterial disease

Purpose: Although it is known that peripheral arterial disease (PAD) is associated with chronic myopathies, the acute muscular responses to exercise in this population are less clear. This study used diffusion tensor imaging (DTI) to compare acute exercise-related muscle damage between PAD patients and healthy controls. Methods: Eight PAD patients and seven healthy controls performed graded plantar flexion in the bore of a 3T MRI scanner. Exercise began at 2 kg and increased by 2 kg every 2 min until failure, or completion of 10 min of exercise. DTI images were acquired from the lower leg pre- and post-exercise, and were analyzed for mean diffusivity, fractional anisotropy (FA), and eigenvalues 1–3 (λ_1–3) of the medial gastrocnemius (MG) and tibialis anterior (TA). Results: Results indicated a significant leg by time interaction for mean diffusivity, explained by a significantly greater increase in diffusivity of the MG in the most affected legs of PAD patients (11.1 × 10^–4 ± 0.5 × 10^–4 mm²/s vs. 12.7 × 10^–4 ± 1.2 × 10^–4 mm²/s at pre and post, respectively, P = 0.02) compared to healthy control subjects (10.8 × 10^–4 ± 0.3 × 10^–4 mm²/s vs. 11.2 × 10^–4 ± 0.5 × 10^–4 mm²/s at pre and post, respectively, P = 1.0). No significant differences were observed for the TA, or λ_1–3 (all P ≥ 0.06). Moreover, no reciprocal changes were observed for FA in either group (all P ≥ 0.29). Conclusion: These data suggest that calf muscle diffusivity increases more in PAD patients compared to controls after exercise. These findings are consistent with the notion that acute exercise results in increased muscle damage in PAD.