CHICAGO -- The loss of mental sharpness suffered by many heart-bypass patients several months after surgery may not be caused by the heart-lung machine used in the operating room after all, a study suggests.
The research found that mental decline also occurred in bypass patients who had been put on a newer device that does not require stopping the heart.
Tens of thousands of bypass patients each year suffer mental decline after surgery, including difficulty thinking and remembering. The condition may not show up for several months and can last for years. One leading theory is that the heart-lung machine is the culprit.
The Dutch study compared results in heart-lung machine patients with those put on an "off-pump" device that only partially immobilizes the heart. Off-pump patients had less mental decline than heart-lung patients at three months, but the differences became negligible a year after surgery.
The Dutch researchers said one possible explanation is that the off-pump device might also contribute to mental decline. But they also theorized that anesthesia, used in both procedures, or the trauma of surgery itself might affect mental functioning.
American Heart Association spokesman Dr. Irving Kron, a University of Virginia cardiologist, said the study adds to the mystery.
The study appears in today's Journal of the American Medical Association.