Myocardial Preservation During Cardiac Surgery Concepts and Controversies

Abstract

Summary The challenge of myocardial preservation during cardiac surgery has gone through many stages since the problem was first encountered in the 1950s. The current foundation is based on blood or crystalloid solutions containing potassium concentrations ranging from 15 to 30 mM. Although the timing of induction of myocardial hypothermia is controversial, the reduction of myocardial temperature still forms an integral part of current preservation techniques. Increased understanding of the metabolic needs of the heart and the pathophysiology involved in myocardial ischemia has facilitated the development of better methods of cardiac protection. Although the basic premise of rapid arrest, uniform cooling, and minimal ischemic time still provide the formula for a successful outcome, new clinical demands continually test the ability to attain these goals. Patients with severe acute ischemic heart disease present for emergency myocardial revascularization and others require the repair of complex congenital cardiac lesions. The demands of myocardial transplantation necessitate better methods of preservation to permit longer ischemic times and, hopefully, greater donor availability. The ability to meet these demands will require the integration of information gained from the study of myocardial ultrastructure, biochemistry, physiology, pharmacology, and pathology, as well as the application of this data to well-controlled clinical trials. Although this area is controversial, the concepts of myocardial metabolism, calcium homeostasis, and response to injury form the foundation on which future improvements in myocardial preservation will be made.