Stroke occurred more often postoperatively than intraoperatively in more than 45,000 patients who underwent coronary artery bypass grafting at a single center during a 30-year period, according to a report in the Jan. 26 issue of JAMA.
The overall incidence of CABG-related stroke also declined since the late 1980s, even though the risk profiles of patients have been worsening at the same time, with the procedure being performed in recent years in more patients who have hypertension, diabetes, and even a history of stroke, Dr. Khaldoun G. Tarakji and his associates at the Cleveland Clinic reported (JAMA 2011:305:381-90).
They studied the timing of CABG-related stroke because few studies have examined the issue and because "understanding the risk factors specific to the timing ... should be beneficial in identifying the cause of the stroke and developing preoperative, operative, and postoperative strategies to predict and prevent stroke."
Dr. Tarakji and his colleagues reviewed 45,432 consecutive cases of CABG at their center during 1982-2010. Overall, 1.6% of patients developed perioperative stroke.
After peaking at 2.6% in 1988, perioperative stroke declined thereafter by 4.7% per year. "This is most likely the result of improving preoperative assessment, intraoperative anesthetic and surgical techniques, and postoperative care," they noted.
Approximately three-fifths of the patients who developed stroke did so postoperatively, with the incidence peaking at day 2 and reverting to a constant hazard of 0.05% by day 6.
"The inflammatory process and hypercoagulability after surgery might provide some explanation for this peak. Identifying the etiology of this postoperative risk factor for stroke may lead to better strategies to prevent it, whether through more aggressive use of antithrombotic and antiplatelet agents, prophylactic prevention of atrial fibrillation, or both," the investigators wrote.
Surprisingly, new-onset postoperative atrial fibrillation did not raise the risk of postoperative stroke.
"To treat new-onset atrial fibrillation, we initially try early medical conversion or electroconversion and, if AF recurs or is persistent, rate control, and anticoagulation. This strategy appears to be associated with not only preventing an anticipated increased risk of postoperative stroke but perhaps [also] with actually lowering the risk," they noted.
Different surgical techniques carried different risks for intraoperative stroke. "We found off-pump CABG and on-pump beating-heart CABG to be associated with the lowest risk of intraoperative stroke [0.14% and 0%, respectively], on-pump arrested-heart CABG with slightly higher risk [0.50%], and on-pump CABG with hypothermic systemic circulatory arrest with the greatest risk [5.3%]," Dr. Tarakji and his associates wrote.
"Both off-pump CABG and on-pump beating-heart CABG can be performed with minimal aortic manipulation, and therefore they likely lower the risk of stroke by decreasing the risk of aortic atherosclerotic embolization." However, this potential benefit "must be weighed against the greater risk of incomplete revascularization, lower graft patency, and worse 1-year outcomes reported for patients undergoing off-pump CABG."
Intraoperative stroke risk increased with advancing age when surgeons used on-pump arrested-heart CABG or on-pump CABG with hypothermic circulatory arrest, but not when they used off-pump CABG or on-pump beating-heart CABG.
"In patients at high risk of intraoperative stroke, such as the elderly or those with aortic arteriosclerosis, off-pump CABG or on-pump beating-heart CABG with no or minimal aortic manipulation may be best. However, in patients at low risk of stroke, such as those without aortic arteriosclerosis and minimal arteriosclerotic burden, on-pump CABG is likely the best option to provide optimal surgical revascularization and minimal risk of stroke," they wrote.
The investigators cautioned that their data were drawn from a single academic medical center and thus may not be generalizable to all U.S. practice.
The study was funded by the Cleveland Clinic. One of Dr. Tarakji’s coauthors reported receiving honoraria from Medtronic.