Energetics and function of the failing human heart with dilated or hypertrophic cardiomyopathy

Background Impaired energy metabolism in the failing human heart could be a n important mechanism of functional deterioration. The purpose of this stud y was to assess the changes of myocardial energy metabolism in the human he art at end-stage heart failure. Materials and methods The left ventricular myocardium of patients undergoin g heart transplantation due to dilated (DCM, n = 14) or hypertrophic cardio myopathy (HCM, n = 5) and non-diseased donor heart samples (n = 4) were ana lysed for citrate synthase (CS), enzymes of the glycolytic pathway as well as concentrations of phosphocreatine (PCr), creatine (Cr), adenine and guan ine nucleotides. Results Total creatine levels (phosphocreatine + creatine) were significant ly decreased (P < 0.05) in both groups of diseased hearts (3.87 +/- 0.57 in DCM, 5.09 +/- 1.23 in HCM compared with control 10.7 +/- 3.5 mu mol g(-1) wet weight). There was a trend for higher guanine nucleotide content in fai ling hearts, but no significant differences were observed in total adenine nucleotides and total NAD content. CS was markedly reduced (P < 0.05) in bo th groups of diseased hearts: in the DCM to 13.8 +/- 1.3 mu mol min(-1) g(- 1) wet weight, and in HCM to 11.9 +/- 2.4 compared with the control 29.2 +/ - 2.2. Glycolytic enzymes were decreased compared with the control, and thi s decrease was greater in DCM than in HCM. Echocardiographic indices of con tractility were considerably better in hypertrophic cardiomyopathy. Conclusion Despite the different mechanisms of cardiac failure and the diff erences in contractility of the heart we have observed, metabolic changes a re very similar in hypertrophic and dilated cardiomyopathy. Depletion of th e creatine pool suggests an alteration in the intracellular energy reserves and transfer, whereas the decrease in citrate synthase activity suggests r educed oxidative capacity in both dilated and hypertrophic cardiomyopathy.