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Does the Heart/Lung Machine Save the Heart but Hurt the Mind?

No one disputes that coronary artery bypass grafting (CABG) has saved thousands of lives. There's concern, however, that the heart-lung machine, which is used during the traditional procedure, can temporarily affect the brain, resulting in memory loss and other cognitive impairment.

Every operation has complications, and with CABG, there's a risk of stroke, kidney damage, and lung failure. Stopping a heart and transferring the body's circulatory and breathing functions to a machine can also take a toll on the patient's brain. The statistics vary, but cognitive impairment following CABG, as presented by memory loss and/or personality change, has been detected in some patients. For many of them, these problems are less severe a few months after surgery.

There are a number of theories as to why use of the heart-lung machine sometimes affects the brain. One thought is that tiny fat particles called microemboli enter the bloodstream and travel to the brain, where they block capillaries. Another possibility is that the machine does not provide enough oxygen during the operation for some patients.

Similar cognitive difficulties seem to be less prevalent in patients who have had coronary bypass "off-pump," meaning without the use of the heart-lung machine.

A recent study from the Duke University Medical Center links CABG to cognitive decline. Of 261 CABG patients, 53 percent showed impairment when they were released from the hospital; the percentage dropped at six weeks and six months following surgery, but five years later, it rebounded to 42 percent. However, the study did not include a control group, and it's been suggested that other factors, such as the aging process or cerebrovascular disease, contribute to the cognitive decline.

"While this study adds to our knowledge of how the heart-lung machine affects the mind, research in this area continues," says Dr. Ahmed Rajaii Khorasani, director of minimally invasive surgery at University Hospital. "Some patients, fearing the prospect of post-operative cognitive decline, may ask for OPCAB, when CABG is the better choice for them. Both operations have risks and benefits, and it's the surgeon's responsibility to assess each patient's condition and recommend the procedure that is likely to have the best possible outcome."

For more information on cardiovascular health services, visit the NJCI Web site: www.TheUniversityHospital.com/njci