Myocardial Protection

During cardiopulmonary bypass procedures with induced cardiac arrest, the heart is not being normally perfused through the coronary arteries, which results in myocardial ischemia. Minimizing myocardial oxygen demand during surgically induced ischemia is the primary principle of myocardial protection with cardioplegia, which relies on stopping cardiac electro-mechanical activity (induced arrest), and hypothermia (<25 °C). The application of cardioplegic solutions to provide myocardial protection consists of the following main goals: to provide rapid induction of diastolic arrest to eliminate myocardial contraction; to cause hypothermia to decrease myocardial basal metabolic demands; to include appropriate buffering capacity to neutralize the intracellular acidosis that occurs as a result of ischemia; to provide the necessary substrates to facilitate homeostasis during reperfusion; and to help prevent myocardial edema. Cardioplegia solutions are administered in an antegrade or retrograde fashion after the application of the aortic cross clamp during cardiopulmonary bypass. The adequacy of cardioplegia is confirmed by the cessation of electrical and myocardial activity. There are several types of cardioplegia solutions available including crystalloid and blood-based solutions. The two most commonly used formulations today are Buckberg and del Nido cardioplegic solutions.