Myocardial function depends on adenosine triphosphate (ATP) supplied by oxidation of
several substrates. In the adult heart, this energy is obtained primarily from fatty acid oxidation
through oxidative phosphorylation. However, the energy source may change depending
on several factors such as substrate availability, energy demands, oxygen supply,
and metabolic condition of the individual. Surprisingly, the role of energy metabolism in
development of cardiac diseases has not been extensively studied. For instance, alterations
in glucose oxidation and transport developed in diabetic heart may compromise myocardial
performance under conditions in which ATP provided by glycolysis is relevant, such
as in ischemia and reperfusion. In some cardiac diseases such as ischemic cardiomyopathy,
heart failure, hypertrophy, and dilated cardiomyopathy, ATP generation is diminished
by derangement of fatty acid delivery to mitochondria and by alteration of certain key enzymes
of energy metabolism. Shortage of some co-factors such as L-carnitine and creatine
also leads to energy depletion. Creatine kinase system and other mitochondrial enzymes
are also affected. Initial attempts to modulate cardiac energy metabolism by use of drugs
or supplements as a therapeutic approach to heart disease are described.