ORLANDO, FLA. — Age greater than 70 years, abnormal preoperative neurologic status, and prior cardiac surgery are independent risk factors for stroke related to coronary artery bypass graft, Scott Woods, M.D., said at the annual meeting of the American Academy of Family Physicians.
“If you have a patient who needs CABG and has none of these three predictors, which are easy to determine by exam and history in the office, the risk of stroke is 1%,” said Dr. Woods, director of epidemiology at the Bethesda Family Practice Residency Program, Cincinnati. “But if he has all three risk factors, the chance is one in three.”
Cerebrovascular accidents (CVAs) are well-known adverse events associated with CABG surgery, occurring in about 3% of all cases, Dr. Woods said.
“If the predictors of this catastrophic event could be found, we could possibly avoid the events for those at greatest risk,” he said. “That was the purpose of our project.”
Dr. Woods conducted a nested case-control study to identify the risk factors. He used a 9-year, prospective cohort that included 6,245 patients who had CABG between October 1993 and June 2002.
Cases were matched to controls in a one-to-three ratio: There were 171 patients who had a stroke and 513 controls. The CVA rate at the facility was 2.7%, very close to the national average. The study population was primarily white, with few Hispanic and Asian patients.
Dr. Woods considered 38 variables, including medical history and operative factors, such as pump time and perfusion time. Regression analysis uncovered three independent predictors of stroke.
Age older than 70 years was associated with a 4.6-fold increase in risk. Abnormal neurologic findings such as slurred speech or hemiparesis prior to surgery upped the chance of a stroke by a factor of 4.24, and previous cardiac surgery was associated with a 1.75-fold increase in risk.
The research also indicated that if the patient had one of the two stronger predictors—age over 70 or abnormal neurologic findings—the risk was 1 in 25 (4%) that he or she would suffer a CVA associated with the surgery. A patient aged 70 years or older who also had an abnormal neurologic finding during the preoperative exam had a one in five (20%) risk of suffering a CVA. If all three risk factors were present, the chance of suffering a CVA was one in three (33%).
If the patient's risk of stroke is 20% or 33%, “you certainly need to counsel them on it,” Dr. Woods said. The patient may find the risk to be too high. “Obviously, it's a judgment call.”