Myocardial energetics

This chapter assesses myocardial energetics. The heart requires very large amounts of energy, cycling many times its own weight in ATP daily, and uses a variable combination of carbohydrates, lipids, lactate, and amino acids as fuel. A key feature of the healthy heart is ‘metabolic flexibility’, i.e. the ability to use different substrates according to circumstances. As the syndrome of heart failure progresses, a steady downregulation of all aspects of cardiac metabolism may be seen. In extreme disease states, a fundamental deficiency in ATP can be demonstrated, but more subtle metabolic abnormalities are detectable at an earlier stage. Additionally, there are multiple downstream disturbances in mitochondrial function, in the high-energy phosphate pool and in excitation–contraction coupling. Ultimately, the detection of abnormalities of myocardial metabolism and energetics has spurred an interest in therapeutic modulation of metabolism in heart failure. This is attractive, as potentially such modulation would improve myocardial efficiency without the need for increased fuel delivery. Such therapies could have an additive effect to current heart failure management which generally relies on correction of the maladaptive neurohumoral consequences of the heart failure syndrome.