Increased risk and decreased morbidity of coronary artery bypass grafting between 1986 and 1994

The collective impact of advances in medical, surgical, and anesthetic care on the characteristics and outcomes of patients who undergo coronary artery bypass grafting was assessed.

We compared the demographic and clinical characteristics, preoperative risk factors, morbidity, and mortality of two groups of patients who underwent coronary artery bypass grafting in isolation or in combination with other procedures between July 1, 1986, and June 30,1988 (group 1, n = 5,051), and between January 1, 1993, and March 31, 1994 (group 2, n = 2,793). The patients were stratified according to their preoperative risk level. Outcome measures consisted of changes in preoperative risk categories; hospital mortality rates; overall and risk-adjusted major cardiac, neurologic, pulmonary, renal, and septic morbidity rates; and intensive care unit length of stay.

Changes in the distribution of risk categories, from a median of 2 to 4 on a 9-point scale (p < 0.001), indicated that patients in group 2 were at significantly higher risk than those in group 1. The risk-adjusted mortality rate did not change (2.8% to 2.9%; p = 0.15), but the risk-adjusted morbidity rate decreased significantly (14.5% to 8.8%; p < 0.001).

At our institution, patients who undergo coronary artery bypass grafting are now at greater preoperative risk at the time of hospital admission. However, their morbidity rate is significantly lower and their mortality rate is unchanged, results that we attribute to the collective impact of changes in our medical and surgical procedures.