Bypasses May Pose Higher Risk of Strokes, Study Says
Bypass surgery for heart disease--which has become almost a routine procedure in the United States--may cause a much greater incidence of strokes and neurological impairment than physicians had suspected, experts will report today.
Those so-called adverse cerebral events lead to extended hospitalization for as many as 24,000 Americans each year and increase hospital bills by $2 billion to $4 billion annually, according to a report in the New England Journal of Medicine.
The findings “don’t mean that patients shouldn’t have the surgery, because it is often lifesaving, but they should be aware of the risks,” said Dr. Dennis T. Mangano of the Ischemia Research and Education Foundation in San Francisco.
They also cite the need to develop ways to reduce the risk, he said.
Many surgeons had previously thought that less than half of 1% of bypass patients suffered strokes or impairment immediately after surgery, but a major new study conducted on 2,108 patients at 24 major medical centers indicates that the rate is 6.1%.
Bypass surgery is performed on nearly 400,000 American patients each year to replace clogged arteries leading to the heart. In the surgery, healthy blood vessels from elsewhere in the body are used to bypass the clogged arteries, allowing blood to reach the heart.
One major risk factor in bypass surgery is the presence of atherosclerotic or fatty plaques in the region of the aorta where surgical clamps are used when patients are placed on heart bypass, said Dr. Gary W. Roach of Kaiser Permanente Medical Center in San Francisco, a lead author of the study. Disturbed, the plaques can break off and lodge in the brain.
“By identifying the presence and location of these plaques before the operation, we may be able to immediately reduce the number of strokes following coronary bypass surgery,” Roach said.
This is “a very interesting and challenging report,” said Dr. George Sopko of the National Heart, Lung and Blood Institute. “It provides a hard set of data, challenges us to think about mechanisms and challenges us to think about how we can improve.”
But Dr. Timothy J. Gardener of the University of Pennsylvania Medical Center was less impressed. “I don’t think there is anything in the study that most surgeons aren’t already telling their patients,” said Gardener, a member of the American Heart Assn.’s Surgery Council.
“It’s useful for the public to know that bypass surgery, like any other major surgery, involves a potential risk,” he said. “But there’s really nothing new about it.”
Previous studies have shown a broad variation in the incidence of strokes and other brain injuries after bypasses, but all of those studies had design flaws, critics say. Each was conducted at only one institution, had small numbers of patients, and all were done retrospectively--interviewing patients after a stroke had occurred--introducing the possibility of bias.
In the new multi-center study, organized by Mangano, epidemiologists began studying patients before they underwent the surgery and were on the alert for adverse events afterward.
Among the 2,108 patients, the team found that 3.1% had the worst outcomes: eight died of cerebral injury, 55 had nonfatal strokes, two had transient ischemic attacks, or small strokes, and one had stupor.
Another 3% had less severe problems: 55 had deterioration of intellectual functions and eight had seizures. An additional 4%, Mangano said, had milder symptoms of memory loss and impairment that weren’t reversed after six months.
The latter symptoms “are like accelerated aging,” Mangano said.
Patients experiencing the worst outcomes had an additional $10,266 in hospital costs, while those with the less severe outcomes had an additional $6,150, the study found. Many were eventually transferred to nursing homes and others underwent extensive rehabilitation, necessitating further costs.
The study did not examine angioplasty, an alternative procedure in which a balloon is used to flatten plaque in the arteries. About 500,000 Americans undergo angioplasty each year. Surgeons believe that it has a lower incidence of stroke and neurological impairments than bypass, “but, in fact, we don’t know,” Mangano said.
One reason surgeons did not fully appreciate the risks of neurological damage in bypass operations is that earlier studies were done on younger populations, Mangano said.
In 1980, when bypasses were performed on about 100,000 Americans per year, the average age was under 60. Today, the average is in the late 60s. “We expect that by the turn of the century, it will be in the 70s,” Mangano said, “and we know that the risk increases with age.”
In fact, the risk of adverse neurological outcomes doubles between the ages of 60 and 70 and doubles again between 70 and 80, experts agree.
In addition to age, other risk factors for stroke after bypass included a previous stroke or other neurological problems, alcoholism, unmanaged hypertension and lung problems.
Many of these problems can be addressed by surgeons preparing to perform bypass surgery, Mangano said. A new technique called esophageal echo cardiography can be used to determine the location of atherosclerotic plaques in the aorta before surgery, allowing surgeons to place clamps in the regions least affected.
