People born with certain gene more likely to suffer cognitive decline after heart surgery

Thirty to 50 percent of patients experience a decrease in cognitive function after heart surgery and neurologic injury is one of the most common adverse side effects. Examples of neurologic injuries include stroke, memory loss, difficulties with problem-solving and impaired attention.

"Whether cognitive decline seen after surgery is a side effect of the surgery and anesthesia or a progression of other neurologic disease remains a matter of debate," said Karsten Bartels, M.D., who helped conduct this study while a fellow in cardiothoracic anesthesiology and critical care medicine under the direction of Joseph Mathew, M.D., professor of anesthesiology at Duke University Medical Center, Durham, N.C. "Our study found that if a patient has this gene variation (APOE4), that person is more likely to have cognitive decline five years after surgery."

People are born with the gene variation Apolipoprotein E4 (APOE4), which can be identified through a genetic blood test. Apolipoproteins are important gatekeepers of cholesterol metabolism and inflammation, according to Dr. Bartels. The protein structure of these apolipoproteins is determined by a person's DNA; however, minor variations are not uncommon. Such minor variations in the genetic code can have serious consequences. APOE4 has been identified as both a driver and marker of accelerated neurologic dysfunction, including in Alzheimer's disease.

In the study, the authors reviewed data from 233 elderly, Caucasian cardiac patients who had heart surgery. The patients were administered a battery of neuropsychological assessments just before surgery and five years after. Cognitive function was assessed with a composite cognitive index score. The change in cognitive function five years after surgery was adjusted for age, years of education and cognitive score prior to surgery.

The study found that the mean change in cognitive index score over five years for patients without the gene variation was 0.16, while the score for patients who have the APOE4 gene variation was .08. These results indicate a less favorable outcome for carriers of the APOE4 gene.

"Our findings suggest that the long-term cognitive decline previously seen after surgery is related more to the patient's genetic makeup than to the surgery itself," continued Dr. Bartels. "Knowing which patients have the APOE4 genotype can help doctors assess the risk for cognitive problems following surgery, ultimately allowing patients to make better-informed decisions and permitting doctors to direct strategies to protect the brain after surgery."