Dynamic magnetic resonance measurements of calf muscle oxygenation and energy metabolism in peripheral artery disease.

Clinical assessments of peripheral artery disease (PAD) severity are insensitive to pathophysiological changes in muscle tissue oxygenation and energy metabolism distal to the affected artery.To quantify the blood oxygenation level-dependent (BOLD) response and phosphocreatine (PCr) recovery kinetics on a clinical MR system during a single exercise-recovery session in PAD patients.Case-control study.

Fifteen Fontaine stage II patients, and 18 healthy control subjects FIELD STRENGTH/SEQUENCE: Interleaved dynamic multiecho gradient-echo ¹ H T₂ * mapping and adiabatic pulse-acquire ³¹ P-MR spectroscopy at 3T.

Blood pressure in the arms and ankles were measured to determine the ankle-brachial index (ABI). Subjects performed a plantar flexion exercise-recovery protocol. The gastrocnemius and soleus muscle BOLD responses were characterized using the T₂ * maps. High-energy phosphate metabolite concentrations were quantified by fitting the series of ³¹ P-MR spectra. The PCr recovery time constant (τ_PCr ) was derived as a measure of in vivo mitochondrial oxidative capacity.

Comparisons between groups were performed using two-sided Mann-Whitney U-tests. Relations between variables were assessed by Pearson's r correlation coefficients.

The amplitude of the functional hyperemic BOLD response in the gastrocnemius muscle was higher in PAD patients compared with healthy subjects (-3.8 ± 1.4% vs. -1.4 ± 0.3%; P < 0.001), and correlated with the ABI (r = 0.79; P < 0.001). PCr recovery was slower in PAD patients (τ_PCr = 52.0 ± 13.5 vs. 30.3 ± 9.7 sec; P < 0.0001), and correlated with the ABI (r = -0.64; P < 0.001). Moreover, τ_PCr correlated with the hyperemic BOLD response in the gastrocnemius muscle (r = -0.66; P < 0.01).

MR readouts of calf muscle tissue oxygenation and high-energy phosphate metabolism were acquired essentially simultaneously during a single exercise-recovery session. A pronounced hypoxia-triggered vasodilation in PAD is associated with a reduced mitochondrial oxidative capacity.2 Technical Efficacy: Stage 1 J. Magn. Reson. Imaging 2019.