Noninvasive detection and monitoring of regional myocardial ischemia in situ using depth-resolved 31P NMR spectroscopy.

Phosphorus (31P) NMR spectra showing the relative concentrations of phosphocreatine, ATP, and Pi were recorded noninvasively from localized regions in the left ventricles of dog hearts in situ by using depth-resolved surface-coil spectroscopy at 1.5 T. Proton (1H) NMR surface-coil imaging was used to position 31P NMR coils and to determine the location of depth-resolved volumes immediately prior to 31P examination. Occlusion of the left anterior descending coronary artery produced regional ischemia detected as changes in the ratios of phosphocreatine, ATP, and Pi and by changes in the pH measured from the spectra. Spectral changes were not typically observed in regions adjacent to ischemic myocardium. Reperfusion produced some recovery, and ventricular fibrillation resulted in deterioration in high-energy metabolites. The location and size of ischemic tissue was measured by single-photon-emission computed tomography (SPECT) and gamma-ray counting or by staining excised hearts. The technique should permit the long-term noninvasive monitoring of the metabolic response of the heart to pathologic processes and allow assessment of interventions.