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Reducing risk in the CABG patch

By Amanda Thornton

One of the most common surgeries in the U.S. is a coronary artery bypass graft (CABG). If the arteries supplying the heart are blocked, healthy blood vessels can be harvested from elsewhere in the body and grafted onto the heart. But though half a million CABGs are performed each year, the procedure carries a risk of kidney failure. There have long been ways to predict renal failure in patients who already had kidney problems. Dartmouth researchers have now developed a way to predict post-CABG renal failure in patients whose kidneys were working just fine before surgery.

Function: "Three percent of [patients] with normal kidney function going into surgery are walking out with severe renal dysfunction," explains Jeremiah Brown, Ph.D., lead author of the paper in Circulation that reported the method. "It's a problem we need to address." Brown's team—which included cardiologist David Malenka, M.D.; epidemiologist Gerald O'Connor, Ph.D., Sc.D.; and others—collected data on 11,301 patients. All had had CABGs between 2001 and 2005 at hospitals in the Northern New England Cardiovascular Disease Study Group, a consortium cofounded by O'Connor in 1987.

The new renal failure model calculates risk based on the sum of point values assigned to various patient

Brown, right—with O'Connor, left, and Malenka—created a risk-prediction tool.

characteristics. The team identified two key risk factors: congestive heart failure and the use during the CABG of an emergency intra-aortic balloon pump—a tiny balloon inserted in the aorta to help the heart pump blood. Other risk factors include being over 70 and female, having had a prior CABG, and having an elevated white-blood-cell count, diabetes, peripheral vascular disease, or hypertension. "The unfortunate issue,"

says Brown, "is that very few of these variables are modifiable."

Nevertheless the prediction tool is expected to help. "When we recognize that a patient is at increased risk for post-procedural renal dysfunction, there are a variety of changes we can make in their care to minimize that risk," says Malenka, including carefully monitoring the patient's kidneys after surgery.

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