Abnormal myocardial phosphorus-31 nuclear magnetic resonance spectroscopy in women with chest pain but normal coronary angiograms

Background: After hospitalization for chest pain, women are more likely tha n men to have normal coronary angiograms. In such women, myocardial ischemi a in the absence of clinically significant coronary-artery obstruction has long been suspected. Most methods for the detection of the metabolic effect s of myocardial ischemia are highly invasive. Phosphorus-31 nuclear magneti c resonance (P-31-NMR) spectroscopy is a noninvasive technique that can dir ectly measure high-energy phosphates in the myocardium and identify metabol ic evidence of ischemia. Methods: We enrolled 35 women who were hospitalized for chest pain but who had no angiographically significant coronary-artery obstructions and 12 age - and weight-matched control women with no evidence of heart disease. Myoca rdial high-energy phosphates were measured with P-31-NMR spectroscopy at 1. 5 tesla before, during, and after isometric handgrip exercise at a level th at was 30 percent of the maximal voluntary grip strength. We measured the c hange in the ratio of phosphocreatine to ATP during exercise. Results: Seven (20 percent) of the 35 women with chest pain and no angiogra phically significant stenosis had decreases in the phosphocreatine:ATP rati o during handgrip that were more than 2 SD below the mean value in the cont rol subjects without chest pain. There were no significant differences betw een the two groups with respect to hemodynamic variables at rest and during handgrip, risk factors for ischemic heart disease, findings on magnetic re sonance imaging and radionuclide perfusion studies of the heart, or changes in brachial flow during the infusion of acetylcholine. Conclusions: Our results provide direct evidence of an abnormal metabolic r esponse to handgrip exercise in at least some women with chest pain consist ent with the occurrence of myocardial ischemia but no angiographically sign ificant coronary stenoses. (N Engl J Med 2000;342:829-35.) (C)2000, Massach usetts Medical Society.