Energy metabolism and mechanical function in perfused hearts of Syrian hamsters with dilated or hypertrophic cardiomyopathy.

Energy metabolism was assessed in dilated (congestive) and hypertrophic myopathic hearts from Syrian hamsters after isolated, working heart perfusion with palmitate and/or glucose as substrates. Hearts with these two types of cardiomyopathy were found to be distinctively different from control hearts, and also different from each other. Both cardiomyopathic groups had developed hypertrophy by 3 months but the dilated hearts had a decreased muscle mass by 6 months. In the hypertrophic hearts coronary flow rates per gram of non-collagen protein and, thus, oxygen delivery were markedly increased. With either substrate the hypertrophic hearts maintained more normal levels of adenosine triphosphate in contrast to the dilated hearts whose levels were approximately 50% lower than controls by 6 months of age despite similar heart rates and left ventricular systolic pressure development in all three groups. Lactate to pyruvate ratios in the diseased hearts were comparable to control values. Total coenzyme A levels were statistically lower in the dilated compared to the control group of hearts. Carnitine and its acyl esters, on the other hand, varied markedly with levels of total carnitine decreasing to 50% of control levels in both cardiomyopathic groups by 6 months. In spite of this, the mass action ratios for the carnitine acyl-CoA transferase enzyme complexes were not markedly altered in the control or myopathic hearts regardless of whether palmitate and/or glucose were the perfusate substrates. These results suggest that the decreased carnitine levels are not of sufficient magnitude at this stage in the disease to cause a decrease in cardiac function secondary to restricted energy production. Total carnitine levels were found to be increased in liver and serum of the cardiomyopathic hamsters but unchanged in skeletal muscle. Thus, the deficiency in myocardial carnitine would appear to be due to a specific myocardial problem and not due to a problem of synthesis or supply.