Intraoperative myocardial protection: Current trends and future perspectives

Background. The results of contemporary coronary artery bypass graft surgery (CABG) are excellent. However, recently changing trends in the population at risk have necessitated new measures to minimize perioperative morbidity and mortality. Methods. We reviewed cardioplegic innovations developed, evaluated, and currently employed at the Toronto Hospital. In addition, we conducted an evaluation of novel cardioplegic formulations, with an eye towards future clinical applications. Results. At the Toronto Hospital, we demonstrated that blood provided better protection than crystalloid cardioplegia. Subsequently, we found that a terminal infusion of warm blood cardioplegia repleted myocardial adenosine triphosphate (ATP) levels and improved postoperative ventricular function. Recently, we reported that tepid (29 degrees C) cardioplegia reduced lactate and acid production during cardioplegic arrest, and improved postoperative ventricular function. Combining antegrade and retrograde cardioplegic delivery reduced lactate production, preserved ATP stores, and improved metabolic recovery after cross-clamp release. Cardioplegic flows of at least 200 mL/min were required to washout detrimental metabolic end-products and improve ventricular function. To further optimize myocardial protection, attempts have been made to harness the beneficial effects of ischemic preconditioning using adenosine. Similarly, insulin cardioplegia has been employed in order to enhance ventricular performance by stimulating early postoperative aerobic metabolism. Finally L-arginine, a nitric oxide donor has been demonstrated to be beneficial in experimental studies and may represent a further option for the enhancement of intraoperative myocardial protection. Conclusions. Despite continued improvements in cardioplegic techniques, low output syndrome following high-risk CABG remains an ongoing concern. The development of novel additives with various protective properties may provide added protection, allowing for a reduction morbidity and mortality following CABG. (C) 1999 by The Society of Thoracic Surgeons.