Myocardial Phosphocreatine-to-ATP Ratio Is a Predictor of Mortality in Patients With Dilated Cardiomyopathy

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Abstract
Background In patients with heart failure due to dilated cardiomyopathy, cardiac energy metabolism is impaired, as indicated by a reduction of the myocardial phosphocreatine-to-ATP ratio, measured noninvasively by 31 P-MR spectroscopy. The purpose of this study was to test whether the phosphocreatine-to-ATP ratio also offers prognostic information in terms of mortality prediction as well as how this index compares with well-known mortality predictors such as left ventricular ejection fraction (LVEF) or New York Heart Association (NYHA) class. Methods and Results Thirty-nine patients with dilated cardiomyopathy were followed up for 928±85 days (2.5 years). At study entry, LVEF and NYHA class were determined, and the cardiac phosphocreatine-to-ATP ratio was measured by localized 31 P-MR spectroscopy of the anterior myocardium. During the study period, total mortality was 26%. Patients were divided into two groups, one with a normal phosphocreatine-to-ATP ratio (>1.60; mean±SE, 1.98±0.07; n=19; healthy volunteers: 1.94±0.11, n=30) and one with a reduced phosphocreatine-to-ATP ratio (P =.036) and cardiovascular ( P =.016) mortality for patients with normal versus patients with low phosphocreatine-to-ATP ratios. A Cox model for multivariate analysis showed that the phosphocreatine-to-ATP ratio and NYHA class offered significant independent prognostic information on cardiovascular mortality. Conclusions The myocardial phosphocreatine-to-ATP ratio, measured noninvasively with 31 P-MR spectroscopy, is a predictor of both total and cardiovascular mortality in patients with dilated cardiomyopathy.