Advances In Myocardial Protection

Abstract

In 1975, anesthesiologists at the Cardiovascular Institute and Fu Wai Hospital began myocardial protection by perfusing cold crystalloid cardioplegic solutions into the ascending aorta. Since then, both clinical and basic research has been directed toward optimal myocardial protection. Current efforts have focused on the components of the arresting solution, the cardioplegic perfusate temperature, and perfusate methods. I. COMPONENTS OF THE ARRESTING SOLUTION a) Blood cardioplegia: (4/5 blood added to 1/5 crystalloid solution with a final KCL concentration of 24 mmol/L) Blood cardioplegia has been used in Fu Wai Hospital since 1994 and provides benefits over cold crystalloid cardioplegia [ formula consists of KCl 20 mmol/L, MgCl2 16 mmol/L, CaCl2 1.2 mmol/L, Procaine 0.9 mmol/L, pH 6.9, osmoality 340 mOsm/L]. More than 5,000 open-heart operations have been performed with blood cardioplegia in the years of 1994 to 1996. A special perfusion device has been developed to provide cold blood cardioplegia, hyperkalemic warm blood cardioplegia or simple oxygenated blood perfusion. To evaluate the effects of blood cardioplegia, 496 patients undergoing open-heart surgery were randomized into two groups. Each group either received cold crystalloid cardioplegia ( n=165) or cold blood cardioplegia ( n=331). Cardioplegic solution was infused in an intermittent anterograde fashion in both groups. The results demonstrated no significant difference in myocardial oxygen consumption. The blood cardioplegia did, however, result in more prompt resumption of lactate extraction and lower levels of released myocardial-specific isoenzyme, creatinine phosphokinase (CK-MB), during reperfusion. Tissue samples were taken from the right atrium 5 minutes before the heart was arrested and 15 minutes after cross clamp removal. Pathological studies in these two groups demonstrated more severe damage to the myocardial ultrastructure in the crystalloid group. Ultrastructure damage was mainly detected in the part of myocardial mitochondria. Myocardium perfused with blood cardioplegic solution demonstrated a more rapid establishment of cardiac rhythm (65%) compared to the crystalloid solution (45%). b) Leukocyte filtered blood cardioplegia (LCBC) To investigate the effects of leukocyte filtered blood cardioplegia on cardiac tissue, a prospective randomized study was performed on 20 patients undergoing valve replacement with myocardial protection by blood cardioplegia (BC) ( n=10 ) or LCBC (n=10 ). Both groups had adequate cardiac arrest during the procedure. Plasma levels of CK-MB were significantly lower in LCBC group than in BC group. Ultrastructure analysis of the myocardium demonstrated damage in the BC group while the LCBC group demonstrated little damage. LCBC may provide superior myocardial protection to blood cardioplegia.