Genes Predict Kidney Complications After Bypass Surgery
Finding could lead to a test that identifies patients at risk
WEDNESDAY, March 2, 2005 (HealthDay News) -- Variants of genes involved in inflammation and blood vessel constriction can hint at the likelihood of kidney damage occurring during heart bypass surgery, a new study finds.
Kidney damage after such operations affects one out of every 12 patients; 750,000 people worldwide have bypass surgery every year, the researchers noted. Until now, there has been no way of predicting which patients are at risk for this serious complication.
But Duke University researchers have found that people with these particular gene variants are two to four times more likely to suffer kidney damage after undergoing heart surgery, according to their report in the March issue of the American Journal of Kidney Disease.
"There are a number of these genetic variants that are common, that seemed to predict that the kidneys would not function as well after surgery," said study author Dr. Mark Stafford-Smith, an associate professor of anesthesiology in the cardiac division.
In their study, Stafford-Smith's team collected data on nearly 1,700 patients undergoing heart surgery. The researchers analyzed blood samples from the patients to determine the genetic makeup of 12 specific mutations on seven genes. These specific genes were chosen because earlier studies had found that they were associated with kidney damage.
Since race also has been shown to be a predictor of kidney damage, Stafford-Smith's group analyzed results for whites and blacks separately.
Among whites, the researchers found those who had two gene mutations, namely, angiotensinogen 842C and interleukin 6-572C, had a 55 percent reduction in kidney function. "This is equivalent to losing a kidney," Stafford-Smith said.
Among blacks, two mutations involved in vascular responsiveness -- endothelial nitric oxide synthase 849T and angiotensin-converting enzyme deletion allele -- led to a 162.5 percent increase in creatinine in the blood. This translates into a 60 percent reduction in the kidney's filtering ability, a rate more than twice as high as the study population as a whole.
Stafford-Smith added he hopes a test might be developed to identify patients who are at risk for this serious complication so they can be given alternative therapies.
"There are other ways of treating coronary artery disease," Stafford-Smith said. "Stents and even medicine are alternatives. If you knew this genetic background, maybe that would tip the balance."
Stafford-Smith said his group needs to show this finding in other patient populations. If their results are confirmed, then the researchers hope to develop a test that could identify patients at risk for kidney problems before surgery.
"We might be able to do genetic tests that would allow us to predict those people who might sustain more problems for their surgery than benefits. And that would influence the way we make decisions about their care," Stafford-Smith said.
Dr. Peter W. Barrett, an assistant professor of surgery and director of the adult cardiothoracic intensive care unit at Yale-New Haven Hospital and Yale University School of Medicine, said, "The paper is very important in identifying reasons for acute renal failure in the post-cardiac bypass patient."
Barrett believes this finding may lead to a preoperative blood test to identify patients at risk for acute renal failure. "Post-operative renal failure carries up to a 20 percent mortality rate," he noted. "This is a well-done study, which is of great value."
The American Heart Association can tell you more about heart-bypass surgery.