NORMAL HIGH-ENERGY PHOSPHATE RATIOS IN STUNNED HUMAN MYOCARDIUM

Objectives. We sought to investigate whether alterations in cardiac hi gh energy phosphates occur in postischemic ''stunned'' human myocardiu m. Background. Transient postischemic myocardial dysfunction is a comm on phenomenon that occurs in a variety of clinical settings in the abs ence of necrosis, and its pathogenesis is still unclear. Cardiac high energy phosphates are reduced during ischemia, and persistently altere d myocardial high energy phosphate metabolism has been suggested as a mechanism contributing to stunning. Methods. We studied 29 patients wi th a first anterior myocardial infarction (MI) who underwent successfu l reperfusion within 6 h of the onset of chest pain. These patients un derwent P-31 magnetic resonance spectroscopy (MRS) a mean of 4 days af ter MI for measurement of left ventricular contractility and relative high energy phosphate metabolites. Twenty-one patients underwent a sec ond P-31 MRS study a mean of 39 days after MI. Eight volunteers served as control subjects. Results. Global and infarct area wall motion sco res improved significantly between the early and late studies. No diff erence nas found between early cardiac phosphocreatine (PCr)/beta-aden osine triphosphate (beta ATP) ratios in patients and control subjects ([mean +/- SD] 1.51 +/- 0.17 vs. 1.61 +/- 0.18, respectively, p = 0.17 ) or between early and late study results in patients (1.51 +/- 0.17 v s. 1.53 +/- 0.17, respectively, p = 0.6). For alpha of 0.05, the study had a 90% power to detect a 9% difference. Conclusions. The results o f this study demonstrate normal myocardial PCr/ATP ratios in patients with myocardial stunning after reperfusion and suggest that relative c ardiac high energy phosphates are not depleted in stunned human myocar dium. (C) 1997 by the American College of Cardiology.