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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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