Reduced expression of the key regulator of cardiac metabolism, transcription factor PPARα, in surgical samples of the auricles from patients with coronary heart disease and heart failure was detected by real-time quantitative PCR. These changes indicate reduced activity of this factor and a shift of energy metabolism from oxidative phosphorylation to glycolysis typical of dedifferentiated cells. Electron microscopy revealed dedifferentiated cardiomyocytes with disassembled contractile apparatus and disorganized sarcomeres. In the examined specimens from patients with heart failure, severe myocardial fibrosis was revealed.