Regional Myocardial Metabolism of High-Energy Phosphates during Isometric Exercise in Patients with Coronary Artery Disease

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Abstract
The maintenance of cellular levels of high-energy phosphates is required for myocardial function and preservation. In animals, severe myocardial ischemia is characterized by the rapid loss of phosphocreatine and a decrease in the ratio of phosphocreatine to ATP. To determine whether ischemic metabolic changes are detectable in humans, we recorded spatially localized phosphorus-31 nuclear-magnetic-resonance (31P NMR) spectra from the anterior myocardium before, during, and after isometric hand-grip exercise. The mean (±SD) ratio of phosphocreatine to ATP in the left ventricular wall when subjects were at rest was 1.72±0.15 in normal subjects (n = 11) and 1.59±0.31 in patients with nonischemic heart disease (n = 9), and the ratio did not change during hand-grip exercise in either group. However, in patients with coronary heart disease and ischemia due to severe stenosis (≥70 percent) of the left anterior descending or left main coronary arteries (n = 16), the ratio decreased from 1.45±0.31 at rest to 0.91±0.24 during exercise (P31P NMR is a useful method of assessing the effect of ischemia on myocardial metabolism of high-energy phosphates and of monitoring the response to treatment. (N Engl J Med 1990; 323:1593–600.)