April 30 (HealthDay News) -- Testing for a gene variant that increases the risk of shock and kidney complications after heart surgery could help guide post-surgery treatment, say Australian and German researchers.

Currently, there are no effective medications to prevent these complications after heart surgery, according to background information in a news release from the American Society of Nephrology. When shock occurs, people are often given norepinephrine to stimulate their blood vessels and normalize their blood pressure, but not everyone metabolizes norepinephrine efficiently.

The reason for this variation in response to norepinephrine is believed to be based in the biological pathways that metabolize the drug and involve an enzyme called catechol-O-methyltransferase (COMT).

In a study of 260 heart bypass patients, the researchers found that a particular genetic variant, called LL, can lower the activity of the COMT enzyme and reduce a person's responsiveness to norepinephrine. People with the LL variant were more likely to develop shock and kidney failure after heart surgery, leading to longer hospital stays, they found.

The study will be published in an upcoming issue of the Journal of the American Society of Nephrology.

If the results are confirmed in larger clinical trials, the researchers said, doctors could test for COMT before heart surgery to determine a person's risk of complications and better prepare for post-surgery care.

SOURCE: American Society of Nephrology, news release, April 30, 2009