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Ischemic heart disease PORT examines in-hospital death rates for CABG patients

By age 60, one of every three men and one of every 10 women show clinical signs of coronary artery disease (CAD). CAD is the culprit in most cases of ischemic heart disease, a condition in which there is an insufficient flow of blood to the heart and, consequently, a high risk of heart attack. The Ischemic Heart Disease Patient Outcomes Research Team (PORT) was funded in 1990 by the Agency for Health Care Policy and Research (HS06503) to conduct a 5-year study of the effectiveness of various surgical and nonsurgical treatments for ischemic heart disease.

The PORT researchers, led by Elizabeth R. DeLong, Ph.D., of Duke University Medical Center, recently published two studies, which are summarized below. The first shows that certain quality improvement interventions can significantly reduce in-hospital deaths following coronary artery bypass graft (CABG) surgery, and the second demonstrates that small coronary artery diameter increases the risk of in-hospital death after CABG surgery.

O'Connor, G.T., Plume, S.K., Olmstead, E.M., and others (1996, March). "A regional intervention to improve the hospital mortality associated with coronary artery bypass graft surgery." Journal of the American Medical Association 275(11), pp. 841-846.

Hospital deaths following CABG surgery can be reduced significantly by training physicians in ways to improve the quality of surgery, providing them with feedback on the outcomes of care they and other doctors provide, and having them make site visits to other medical centers, conclude the Ischemic Heart Disease PORT researchers. They analyzed data on more than 15,000 CABG patients in northern New England between July 1987 and August 1993, to determine the impact of various quality improvement interventions on CABG hospital mortality rates.

The study included all 23 cardiothoracic surgeons practicing in Maine, New Hampshire, and Vermont during the study period. The surgeons received patient outcomes data on their CABG surgeries, surgeries performed by others at the medical centers where they practiced, and data on regional CABG patient outcomes. The participating surgeons attended training sessions on improving surgical care and visited other medical centers to observe the entire process leading to and following CABG surgery.

During the preintervention period, there was no consistent trend in mortality rates. Following the interventions, there were 74 fewer deaths than would have been expected, a significant 24 percent reduction. The researchers conclude that a multi-institutional, regional model for the continuous improvement of CABG surgical care is feasible and effective.

O'Connor, N.J., Morton, J.R., Birkmeyer, J.D., and others (1996, February). "Effect of coronary artery diameter in patients undergoing coronary bypass surgery." Circulation 93(4), pp. 652-655.

Small coronary artery diameter has been associated with an increased risk of death following CABG surgery, perhaps because of the increased likelihood of thrombosis (clotting) in smaller vessels, technical difficulties of operating on smaller vessels, and decreased short-term patency (degree of openness) in bypass conduits grafted to these smaller vessels. This study by the Ischemic Heart Disease PORT shows that small, midleft anterior descending (mid-LAD) coronary artery diameter is associated with a three-fold increase in risk of in-hospital death following CABG surgery.

The PORT investigators recorded the height, weight, sex, age, status at hospital discharge, and diameter of the mid-LAD coronary artery in 1,325 patients undergoing CABG. Results showed that small vessel size was associated with a substantial increase in risk of in-hospital death (15.8 percent for 1-mm vessels, 4.6 percent for 1.5- to 2-mm vessels). Vessel size was strongly related to sex and measures of body size. But after differences in age and body size were controlled for, women still had smaller coronary arteries than men (a mean difference ranging from 0.14 to 0.23 mm). Smaller coronary arteries may explain higher hospital mortality from CABG in women and smaller people, conclude the PORT researchers.

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