MYOCARDIAL METABOLISM
The heart uses ATP, created by metabolism of carbohydrates or fatty acids, to derive energy for contraction and electrical activity. Energy for electrical activity is minimal compared to that required for contraction. Stored energy reserves are scarce, and the heart must continually have a source of energy in order to function. The principal oxidative substrate for ATP production is fatty acid, but if it is not available, a variety of carbohydrates can be used. Myocardial metabolism is aerobic, and a constant supply of oxygen must be available. The heart, unlike skeletal muscle, is unable to acquire an “oxygen debt” because of its inability to utilize anaerobic metabolism.