The role of coronary revascularization in the treatment of ischemic cardiomyopathy

For patients with significant coronary artery disease, abnormal left ventricular (LV) function has predicted an increased risk of death without myocardial revascularization. Natural history studies performed before the advent of coronary bypass surgery established this principle and subsequent comparative studies have confirmed it [1‐ 6]. Soon after the advent of coronary bypass surgery a series of randomized and comparative observational studies were undertaken that compared the strategy of initial bypass surgery with initial medical management followed by surgery if symptoms worsened. Two randomized studies of patients with mild to moderate chronic stable angina, the VA Cooperative Study and the Coronary Artery Surgery Study (CASS), contained patients with abnormal left ventricular function (ejection fraction 50%) [2‐ 4]. In the VA Cooperative Study abnormal left ventricular function and three-vessel disease defined a “high risk” group of patients for whom bypass surgery improved the long-term survival rate. Also in the randomized portion of CASS surgery improved the survival rate of patients with ischemic cardiomyopathy and triple-vessel disease at least out to 10 years after operation. A meta-analysis of these and other smaller randomized trials confirmed the survival benefit of bypass surgery for patients with abnormal LV function [7]. Studies involving the CASS Registry, a nonrandomized portion of the CASS study that contained larger numbers of patients than the randomized arm and contained patients with mild or severe symptoms, showed that surgery prolonged the survival rate of patients with triple-vessel disease and abnormal LV function whether they had mild or severe angina [5, 6]. Other important CASS registry analyses showed that bypass surgery decreased the risk of sudden death for patients with abnormal LV function and that the surgical strategy of complete revascularization was important for patients with ischemic cardiomyopathy [8, 9]. A randomized VA Cooperative Trial involving patients with unstable angina also showed an improved survival rate for patients with triple-vessel disease and abnormal LV function who underwent bypass surgery [10]. All of these trials were initiated within the first decade of bypass surgery. Subsequent to these trials numerous factors have improved the short- and long-term outcomes associated with bypass surgery. Improvements in intraoperative myocardial protection and other aspects of perioperative care have diminished perioperative risks. Vein graft patency rates have been improved by the use of platelet inhibitors [11]. The use of statin-type drugs has been shown to decrease cardiac events within the first 3 years after bypass surgery and to decrease angiographic progression of arteriosclerosis in bypass grafts and native coronary arteries [12, 13]. In the randomized trials internal thoracic artery grafts were rarely used and a mountain of subsequent data has shown that the use of the left internal thoracic artery to graft the left anterior descending coronary artery prolongs the long-term survival rate and reduces the incidence of late cardiac events [14]. Further observational data appear to show that the use of two internal thoracic artery grafts may further improve long-term outcomes [15]. Finally surgeons are better microtechnicians today than they were during the first decade of bypass surgery. The results of the randomized and prospective observational trials and the documented improvements in the outcomes of surgically treated patients since those trials were completed have provided the indications for bypass surgery performed for the purpose of prolonging patient survival. Numerous reviews by multiple consensus panels containing both cardiologists and cardiac surgeons have concluded that the anatomic situations of abnormal LV function combined with left main or multivessel coronary artery disease are anatomic indications for bypass surgery [16, 17]. Within the last decade pharmacologic and electrical treatments for patients with cardiomyopathy have also improved. Angiotensin-converting enzyme inhibitors, beta blockers, and diuretics may improve symptoms of congestive heart failure and in some studies have decreased mortality during short follow-up intervals. In addition implantable defibrillators decreased the risk of death due to arrhythmia in some patient subgroups. These advances have raised the question of whether revascularization is still indicated to improve the survival rate of patients with ischemic cardiomyopathy. Or stated another way, does the existence of uncorrected coronary stenoses still decrease the survival rate of patients with cardiomyopathy in the presence of modern pharmacologic and electrical therapies? It has been suggested that more current randomized trials of patients with ischemic cardiomyopathy are needed to reestablish the indications for bypass surgery. However those trials that do show a benefit of medical therapy indicate that while improvement in mortality has