| Abstract: | The heart requires aerobic energy metabolism to cover the high adenosine triphosphate (ATP) demands when ATP energy reserves are low. Depending on the circulatory supply, heart muscle can switch between the use of various substrates, such as fatty acids, glucose and lactate, hence avoiding substrate deprivation. A highly efficient feed forward control of metabolism and coronary blood flow guarantees the continuous supply with energy under physiological conditions; however, impairment of the energy supply can result from decreased perfusion (flow stop) or increased myocardial diffusion distances (myocardial hypertrophy). Under such conditions the choice of substrate gains importance for maintenance of cardiac energy metabolism. While the energy content of fatty acids is high, the energy efficiency is much lower than that of carbohydrates. The combination of fasting, stress, flow stop, and heparin supplementation during cardiac surgery creates an unfortunate condition for efficient myocardial energy metabolism, because plasma levels of fatty acids are typically enhanced. Metabolic interventions aim to lower fatty acid concentrations in plasma and to increase myocardial glucose uptake, e.?g. by normoglycemic insulin-glucose infusion. The aim is the optimization of energy metabolism to decrease perioperative mortality and the duration of intensive care treatment of patients undergoing cardiac surgery. |
