Since its introduction in the 1960s, coronary artery bypass grafting (CABG) has offered millions of Americans renewed health and longer lives. But, for some, this surgery affects their ability to concentrate and remember. These cognitive changes can occur right after surgery and, in some cases, be long-lasting.

What Happens?

A number of factors likely work together to cause the mental changes.

Bypass surgery is done to treat coronary artery disease (CAD). CAD occurs when fatty plaque builds up in the arteries that supply the heart with oxygen. This buildup blocks blood flow to the heart muscle. During the surgery, doctors route blood flow around the blockages by using vessels from other parts of the body to restore blood flow. In the typical surgery, a patient is placed on a heart-lung machine, their heart is stopped, and the machine supplies the body with oxygen during the operation.

Debate continues in the medical field as to whether the heart-lung machine plays a role in cognitive changes. One theory is that tiny air bubbles or blood clots could break off and travel to the brain, causing damage. Others suggest that the machine may not provide enough oxygen to the brain.

Newer techniques allow doctors to redirect blood flow without stopping the heart or using the heart-lung machine. But the success of these procedures in regards to cognitive changes is still being investigated. Doctors are also exploring other factors that may be contributing to concentration and memory problems after the surgery.

In addition, the same disease process that caused the heart’s blood vessels to clog is also likely clogging the arteries that supply the brain. In one study, patients given a battery of seven cognitive performance tests showed memory problems before surgery, though the changes were subtle. After the surgery, patients showed new cognitive impairments.

“When you expose a brain that’s already vulnerable (because of the arterial disease) to a major stressor like bypass surgery, you see new manifestations of problems,” says Julian Keith, PhD, lead author of this study.

Who Is at Risk?

Researchers at Duke University found that age and having less formal education increased a person’s risk of long-term cognitive problems. Some speculate that the increased risk in age could be due to older adults being more likely to have existing cerebral disease, or younger people better tolerating decreases in brain blood flow during surgery. More education may increase the patient’s ability to compensate for cognitive difficulties, but doctors are still studying the reasons for this.

As more information on cognitive decline and CABG is gained, doctors may due a risk assessment that includes tests to check for brain disease. Dr. Keith thinks educating patients about the risk would help them to better adapt if these changes occur.

What Is Being Done?

Dr. Desvigne-Nickens of the Cardiovascular Medicine Research Group hopes making small changes to the surgery will help prevent cognitive problems. She also believes that these memory and concentration problems may be reversible, meaning there is the potential for treatment. Scientists continue to investigate strategies to protect the brain.

Greater use of angioplasty offers some patients an option. During this cardiac procedure, a doctor inserts a catheter (with a balloon) into an artery in the arm or groin. This catheter is threaded through the vessel to the heart, where the balloon is inflated and opens the artery. Doctors now typically place a mesh stent in the artery to keep it open. But, not everyone is a candidate for the less invasive procedures. If you need CABG and are concerned about cognitive problems, talk to your doctors. They can assess your risk based on your medical history, current health condition, age, and other factors.