Normal myocardial metabolism: Fueling cardiac contraction

The heart has the largest metabolic demand per gram of any organ in the body. Adequate amounts of chemical fuel, namely adenosine triphosphate (ATP), must be generated to support the heart's contractile demands and maintain viability. Fatty acids, ketone bodies, and carbohydrates are the primary substrates of the heart metabolized to generate ATP. Optimal cardiac function depends on the efficient matching of energy generation pathways to energy expenditure. This balance requires the close communication and regulation of various metabolic pathways. Fatty acids are the major source of acetyl coenzyme A for the Krebs cycle and of the oxidative production of ATP. Glycolysis converts glucose to pyruvate and provides a relatively small amount of ATP to the normal adult heart. An understanding of the integration of cardiac metabolism in the well-oxygenated state is important in appreciating deranged cardiac metabolism observed in pathologic states, such as cardiac ischemia and heart failure.