Abstract

Using nuclear magnetic resonance (NMR), we have examined the relationship of high-energy phosphate metabolism and perfusion in human soleus and gastrocnemius muscles. With 31P-NMR spectroscopy, we monitored phosphocreatine (PCr) decay and recovery in eight normal volunteers and four heart failure patients performing ischemic plantar flexion. By using echo-planar imaging, perfusion was independently measured by a local [inversion-recovery (T1-flow)] and a regional technique (NMR-plethysmography). After correction for its pH dependence, PCr recovery time constant is 27.5 +/- 8.0 s in normal volunteers, with mean flow 118 +/- 75 (soleus and gastrocnemius T1-flow) and 30.2 +/- 9.7 ml.100 ml-1.min-1 (NMR-plethysmography-flow). We demonstrate a positive correlation between PCr time constant and local perfusion given by y = 50 - 0.15x (r2 = 0.68, P = 0.01) for the 8 normal subjects, and y = 64 - 0.24x (r2 = 0.83, P = 0.0001) for the 12 subjects recruited in the study. Regional perfusion techniques also show a significant but weaker correlation. Using this totally noninvasive method, we conclude that aerobic ATP resynthesis is related to the magnitude of perfusion, i.e., O2 availability, and demonstrate that magnetic resonance imaging and magnetic resonance spectroscopy together can accurately assess muscle functional status.