Jan. 25, 2011 -- Fewer patients are suffering strokes following coronary artery bypass graft surgery (CABG), even though there are more instances of older and sicker patients having the surgery than in the past, new research suggests.
The study, published in the Jan. 26 issue of TheJournal of the American Medical Association, tracked more than 45,000 patients who had heart bypass surgeries over the past three decades at the Cleveland Clinic.
During this time, CABG has increasingly been used in older patients with advanced cardiovascular disease as well as other risk factors for stroke.
Despite this change in patient profiles, the incidence of stroke associated with bypass surgery steadily declined at the hospital following a peak rate of 2.6% in 1988.
Between 1982 and 2009, 705 CABG patients, or 1.6%, treated at the medical center suffered strokes either during surgery or soon after surgery.
Types of CABG Surgery
Researchers also examined stroke rates associated with four different CABG strategies:
- Surgeries that did not involve a heart-lung machine (“off pump”).
- Surgeries involving heart-lung machines with or without a beating heart (“on-pump with beating heart” and “on pump with arrested heart”).
- Surgeries involving a heart-lung machine with a process used to cool the body and slow circulation to a near standstill, known as CABG with hypothermic circulatory arrest.
The practice of cooling and then rewarming patients during bypass surgery is done to lower the risk of organ damage, but it has increasingly come under suspicion for raising the risk of stroke.
In the Cleveland Clinic analysis, the highest incidence of stroke during surgery occurred in patients who had CABG that involved hypothermic circulatory arrest.
A total of 5.3% of these patients suffered strokes during surgery, compared to just 0.14% of patients who had off-pump surgeries. None of the patients who had on-pump beating heart surgeries had strokes.
About 40% of strokes occurred during surgery and 58% occurred following surgery. Timing of the stroke was undetermined in 17 patients.
Cleveland Clinic cardiovascular surgeon Joseph F. Sabik III, MD, says while different surgical strategies do appear to involve different stroke risks, this doesn’t mean that one approach is best for all patients.
Patients at high risk for stroke due to age or other risk factors may have better outcomes with off-pump surgery while younger patients with a low risk for stroke who require extensive revascularization may do better with on-pump procedures, he says.
“CABG is not a one-size-fits-all surgery,” he says. “We have multiple tools we can use and different procedures may be appropriate for different patients.”
CABG Risks and Benefits
Sabik speculates that stroke rates among CABG patients are declining because patients are now carefully screened before surgery and because surgical techniques and postoperative care have improved.
But Larry B. Goldstein, MD, who directs the stroke center at Duke University Medical Center, says the Cleveland Clinic findings may not be representative of the nation as a whole.
“These data all came from one hospital, and I don’t know what that tells us about what is happening outside that hospital,” he says.
A recent report from California showed a wide variation in stroke rates among heart bypass patients.
California is the first state to report hospital data on stroke incidence associated with CABG surgery.
While the average stroke rate among CABG patients treated at the 121 California hospitals included in the analysis was 1.3%, one hospital had a rate of 4.1% and three others had rates above 2.5%, according to news reports.
Goldstein says the stroke risks associated with CABG surgery have to be balanced against the risks of not having the surgery.
“Like any other surgery, there are risks,” he says. “If the view is that CABG will result in better quality of life or a reduced risk for death, it is probably a risk worth taking.”