[Metabolism of failing myocardium]

Cardiac function is maintained by a change in chemical high energy to mechanical work. In the stressed heart, there may be a primary disturbance in the energy producing systems and energy utilizing systems. A series of metabolic adaptations occur--increased contractile units and economy of contraction etc.. But failure of adaptation causes the development of heart failure. In the failing myocardium, there are various metabolic changes-loss of myocytes, decreased rate of oxidative phosphorylation, decreased activity of mitochondrial and cytosolic enzymes, which correlate energy production, impairment of calcium transport, decreased sensitivity to catecholamine, decreased response of contractile units, inappropriate production of some humoral factors, such as the renin-angiotensin system or cytokines. In addition, these factors may induce a "vicious cycle". However, a number of problems to be solved still exist.