Although they save thousands of lives annually, heart-bypass surgeries cause lasting brain damage in 6.1 percent of patients, a figure some specialists find surprisingly high, according to a big new study.
The 1-in-16 figure, based on a study of more than 2,100 bypass patients at two dozen hospitals, including three Boston affiliates of Harvard Medical School, is significantly higher than most previous studies, which generally involved only one hospital.
“That’s a frightening figure for an elective procedure,” the study director, Dr. Dennis T. Mangano of the San Francisco Veterans Affairs Medical Center, told the Associated Press.
Writing in today’s New England Journal of Medicine, a team led by Dr. Gary W. Roach of Kaiser-Permanente Medical Center in San Francisco reported that 3 percent of the patients suffered a stroke that caused permanent damage. Eight patients died. Another 3 percent suffered lasting “deterioration of intellectual function” that affected their memory, attention span or mental agility.
Dr. Simon C. Body, director of thoracic anesthesiology at Brigham & Women’s Hospital and an investigator for the study, said it shows that the risk of brain damage “is an issue that patients should raise with their surgeons, as it is one of the most common causes of disability after cardiac surgery.”
Body noted that the study identified eight leading triggers of strokes and serious neurological damage, but that only two involve factors that doctors can control by surgical technique. All the other risk factors involved the patient’s own health and could not be minimized by the surgeon.
Patients at Massachusetts General Hospital and the then-named Beth Israel Hospital were also included in the study, which was conducted from September 1991 to September 1993. A follow-up is now under way.
Overall, doctors said, bypass surgery is worth the risk for most people whose heart conditions cannot be improved with medications or a vein-clearing technique called angioplasty.
In Massachusetts and across the United States, heart disease and heart attacks are the single leading cause of death, and bypass surgery - installing new veins to improve blood flow through the heart - usually adds years to patients’ lives and relieves the painful symptoms of angina. About 400,000 Americans and 400,000 people elsewhere in the world undergo the surgery annually.
But the report serves as a forceful reminder that heart surgery remains risky. Clamping and reconnecting blood vessels can spew particles of fat and clotted blood and that settle in the brain, shutting off the circulation and blocking oxygen from reaching brain cells.