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Since its introduction in the 1960s, coronary artery bypass grafting (CABG) has offered millions of Americans renewed health and longer lives. But, for some, problems with memory and concentration occur after this surgery. These cognitive changes can occur right after surgery and, in some cases, be long-lasting.
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 oxygenation. In the typical surgery, a person 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, people given a battery of cognitive performance tests showed memory problems before surgery, though the changes were subtle. After the surgery, people showed new cognitive impairments.
Adding to this debate, another study did find that cognitive changes occur in people who have undergone CABG. But, interestingly enough, the researchers also added that these cognitive changes did not appear to be any different from the decline seen in people with CAD who were not treated with CABG. The study implies that the mental changes may have nothing to do with the surgery, but more to do with the disease the surgery was treating.
If bypass surgery does pose a risk, researchers at Duke University found that age and having less formal education may increase a person’s chance of long-term cognitive problems. Some speculate that the increased risk from older 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 person’s ability to compensate for cognitive difficulties, but doctors are still studying the reasons for this.
More studies may show that the risk of cognitive decline is really more the result of coronary artery disease and less the result of having CABG. But in the meantime, research is being done see if making small changes to the surgery will help prevent cognitive problems. Scientists continue to investigate strategies to protect the brain.
Greater use of angioplasty offers some people 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. However, 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.
American Psychological Association
National Heart, Lung, and Blood Institute
Mental Health Canada
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Last reviewed January 2016 by Michael Woods, MD Last Updated: 1/14/2016