Coronary artery spasm has been implicated in perioperative cardiac arrest, hemodynamic collapse, and myocardial infarction. It is possible that other perioperative events such as low cardiac output, myocardial irritability, and early coronary artery bypass graft closure may at times be due in part, or entirely to, increased coronary vascular resistance (CVR) secondary to effects of circulating catecholamines, intraoperative cardioplegia, hypothermia, anesthesia, or drug effect. Patients who undergo coronary artery bypass have a different endocrinologic response to operation than valve patients, especially when comparing vasopressin levels and the degree of postoperative hypertension, which may affect coronary vascular resistance and the incidence of coronary spasm. By using a thermodilution catheter placed in the great cardiac vein via the coronary sinus to determine coronary blood flow, it is possible to measure changes in CVR and lactate metabolism in the perioperative period. Reductions in coronary blood flow and alterations in cardiac metabolism during coronary spasm have been documented using a coronary sinus catheter. The purpose of this study is to compare changes in coronary blood flow and resistance, lactate metabolism, and oxygen consumption during and immediately after coronary artery bypass and valve surgery, and to correlate these changes with pharmacologic therapy and clinical events.
