Does size matter? What is your infarct rate after coronary artery bypass grafting?

See related article on page 420. T here is compelling evidence that the 30-day mortality rate after coronary artery bypass grafting (CABG) has been on the decrease over the past 10 years. This conclusion is based, in part, on data from 1991 to 2000 derived and analyzed from both a multisite national voluntary database and a Veterans Administration mandatory database. In the voluntary database, changes in the patient risk profile and outcomes of more than 1 million patients undergoing isolated CABG procedures were analyzed. The results indicated that, over the past decade, patients undergoing CABG were increasingly older and had more comorbidities. This was associated with a 30% increase in the predicted relative risk for mortality, from 2.6% to 3.4%. Despite this increase in risk, however, there was a decrease in the risk-adjusted mortality rate, from 4.8% to 2.9%. A subset analysis of the Medicareaged population revealed an even greater increase in the predicted mortality for this group of patients, from 3.3% to 4.4%. The observed operative mortality rates in patients 65 years and older, however, declined from 5.4% to 4.1%, a relative risk reduction of 24.1%. These findings suggest that we are providing superb care to patients with coronary artery disease amenable to surgical intervention. Possible explanations for the decrease in the observed mortality rate despite an increase in the expected mortality rate over the past decade include the introduction of critical care pathways, surgical service lines, formation of cardiac surgical teams, technical improvements in cardiopulmonary bypass, introduction of new myocardial protection strategies and methodologies, “fast-track” management, and changes in selection criteria. As a consequence, one might be inclined to believe that the mortality rate after CABG has finally reached an acceptable level. Obviously, this is not the case, for the only acceptable mortality after CABG is 0.0%. Moreover, these types of studies do not take into account that the complication rates of death, myocardial infarction (MI), severe ventricular dysfunction, and heart failure after CABG might exceed 10% to 15% in selected patient populations, that nearly two thirds of in-hospital deaths after CABG surgery are related to cardiovascular events, and that the cost to the US health care system could exceed $2 billion. There is also increasing evidence that the incidence of myocardial necrosis after CABG, as measured on the basis of measurement of serum creatine kinase (CK) and its MB isoenzyme (CK-MB), occurs more frequently than previously appreciated and is associated with a significant decrease in medium-term and long-term survival. In 2001, Costa and colleagues reported that only 38.1% of 496 patients who underwent CABG had normal postoperative CK-MB levels. When the CK-MB levels were stratified into cohorts of enzyme increases of normal, 1 to 3 times the upper limits of normal (ULN), 3 to 5 or more times the ULN, and more than 5 times the ULN, the incidence of death at 30 days after CABG was 0.0%, 0.5%, 5.4%, and 7.0%, respectively (P .001 among the 4 groups). Late mortality rates (1 year) for these groups were 1.1%, 0.5%, 5.4%, and 10.5%, respectively. The peak postoperative cardiac enzyme level also strongly correlated with worse clinical outcome (P .009). Steuer and associates reported similar findings in 2002. These investigators examined postoperative serum aspartate aminotransferase and CK-MB levels and their relationship to early cardiac-related death and late survival in 4911 patients who underwent CABG consecutively during a 6-year period. They found that elevated enzyme levels on the first postoperative day greatly increased the risk of From the Department of Surgery, University of Kentucky College of Medicine, Lexington, Ky.