A data analysis of more than 45,000 patients who underwent coronary artery bypass graft (CABG) surgery over the past 30 years finds that the occurrence of stroke after CABG has declined, despite an increase in risk profiles of patients, according to a single-center observational study in the Jan. 26 issue of Journal of the American Medical Association.

“About 250,000 people have coronary artery bypass surgery in the U.S., and stroke can be a devastating complication to the procedure. As surgeons, it is our responsibility to understand this risk,” the study’s corresponding author Joseph F. Sabik III, MD, told Cardiovascular Business News. “Therefore, we were seeking to understand which patients experienced an intra-operative and postoperative stroke following CABG, why they occurred and if the different operative procedures influenced that risk.

“As the SYNTAX trial demonstrated, the difference between PCI and CABG really lies in their complications,” said Sabik, who is chairman of thoracic and cardiovascular surgery at Cleveland Clinic. “The early results of SYNTAX, which compared CABG with PCI for patients in complex disease, showed that the surgical patients were trading the stroke risk with the re-intervention risk with PCI. Therefore, we wanted to see if our center’s data supported the findings of this large-scale, randomized trial.”

Lead author Khaldoun G. Tarakji, MD, MPH, of Cleveland Clinic, and colleagues examined the prevalence and timing of peri-operative stroke, along with associated patient and surgical factors. The study included data from 45,432 patients (average age, 63 years) who underwent primary or re-operative CABG surgery from 1982 through 2009 at its academic medical center.

Strokes occurring following CABG were recorded prospectively and classified as having occurred intra-operative or postoperatively. Data also included information on four different CABG operative strategies: off-pump, on-pump with beating heart, on-pump with arrested heart and on-pump with hypothermic circulatory arrest.

Among the patients in the study, 705 (1.6 percent) experienced a stroke. Occurrence of stroke peaked in 1988 at 2.6 percent. Then, the authors reported that the rate slowly declined by 4.69 percent annually, despite increasing patient risk profile, such as higher prevalence of preoperative stroke, hypertension and diabetes. Of the 705 patients experiencing stroke, intra-operative stroke occurred in 40 percent and postoperative stroke in 58 percent, with timing undetermined in 17 patients.

Risk factors common to both intra-operative and postoperative stroke included older age, previous stroke, preoperative atrial fibrillation and on-pump CABG with hypothermic circulatory arrest. As the number of arteriosclerotic co-existing conditions increased, stroke risk increased.

Different surgical techniques were associated with different risks of intra-operative stroke. Unadjusted rates of stroke were highest among patients who had on-pump CABG with hypothermic circulatory arrest (5.3 percent) and lowest among those who had off-pump CABG (0.14 percent) and on-pump beating-heart CABG (0 percent). Risk of intra-operative stroke was intermediate for those undergoing on-pump arrested-heart CABG (0.50 percent).

“There are certain risk factors associated with stroke; however, by choosing the proper operative technique, we can lower that risk of stroke and lower the risk of intra-operative stroke to similar rates of PCI,” said Sabik. “Additionally, we learned that the risk of stroke has decreased over this 30-year period, despite the fact that the patients have greater risk factors because they are older.”

Patients who experienced a stroke had substantially worse hospital outcomes, even after adjustment for pre-operative factors: 19 percent mortality versus 3.7 percent; 44 percent prolonged ventilation versus 15 percent; and 13 percent renal failure versus 4.3 percent. They also experienced substantially longer intensive care unit and postoperative lengths of stay.

The authors hypothesized that the reason the occurrence of stroke among patients undergoing CABG has decreased over the last three decades despite an increasing patient risk profile may be the result of improving preoperative assessment, intra-operative anesthetic and surgical techniques, as well as postoperative care.

“Importantly, we can lower the risk of stroke by choosing the right procedure for the right patient,” Sabik said. “For instance, if we have an elderly patient who has extensive atherosclerosis or previous stroke, this patient would clearly benefit from an off-pump procedure. Conversely, for a younger patient without many risk factors, who is undergoing a complex arterial revascularization, this operator can just as easily utilize on-pump without increasing the stroke risk.

“We no longer have one method of undertaking CABG, but we have several ways, which need to be chosen according to what is best for the specific patient’s profile,” Sabik noted. “If we individualize treatment, stroke doesn’t have to be a trade-off between CABG and PCI.”

"Further studies are needed to develop better strategies to minimize the occurrence of stroke among patients undergoing CABG," Tarakji and colleagues concluded.