Occurrence of stroke after coronary artery bypass graft surgery appears to be decreasing, study shows

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Occurrence of stroke after coronary artery bypass graft surgery has declined, despite an increase in risk profiles of patients showed data collected for three decades, among more than 45,000 patients who underwent this type of surgery at an academic medical centre in the USA. The study was published in the January 26 issue of the Journal of the American Medical Association.

Stroke is a devastating and potentially preventable complication of coronary artery bypass surgery. Because it increasingly is being reserved for elderly patients with extensive coronary disease and co-existing conditions, prevalence of stroke after this procedure is likely to remain substantial. Many studies have identified patient factors associated with post-surgery stroke; however, information about timing of perioperative stroke and the influence of different surgical techniques remains limited, according to background information in the article.

 

Khaldoun G. Tarakji of the Cleveland Clinic, and colleagues examined the prevalence and timing of perioperative stroke, along with associated patient and surgical factors. The study included data from 45,432 patients (average age, 63 years) who underwent primary or reoperative coronary artery bypass graft surgery from 1982 through 2009 at an academic medical centre in the USA.

 

Strokes occurring following the graft procedure were recorded prospectively and classified as having occurred intraoperative or postoperatively. Data also included information on four different surgery operative strategies: off-pump (not on heart-lung machine), on-pump with beating heart, on-pump with arrested heart, on-pump with hypothermic circulatory arrest (in which a heart-lung machine is used to cool the body during surgery, which lowers blood pressure and slows circulation to near standstill).

 

Among the patients in the study, 705 (1.6%) experienced a stroke. Occurrence of stroke peaked in 1988 at 2.6%, then slowly declined by 4.69% per year, despite increasing patient risk profile, such as higher prevalence of preoperative stroke, hypertension, and diabetes. Of the 705 patients experiencing stroke, intraoperative stroke occurred in 40% (n = 279) and postoperative stroke in 58% (n = 409), with timing undetermined in 17 patients.

 

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

 

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

 

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

 

The authors speculate that the reason the occurrence of stroke among patients undergoing coronary artery bypass graft has decreased over the last 3 decades despite an increasing patient risk profile may be the result of improving preoperative assessment, intraoperative anesthetic and surgical techniques, and postoperative care.

 

“Further studies are needed to develop better strategies to minimise the occurrence of stroke among patients undergoing coronary artery bypass graft,” the researchers conclude.

 

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