Occurrence of Stroke After CABG Surgery Appears To Be Decreasing

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Over the past 30 years, the occurrence of stroke after coronary artery bypass graft (CABG) surgery has decreased to 1.5% according to a study in the January 26 issue of JAMA.

Khaldoun G. Tarakji, M.D., M.P.H., of the Cleveland Clinic, and colleagues analyzed data on more than 45,000 patients who CABG surgery at an academic medical center over the years 1982 through 2009. They examined the prevalence and timing of perioperative stroke, along with associated patient and surgical factors.

Stroke is a devastating and potentially preventable complication of CABG surgery. Risks factors of stroke in the general population include elderly age, sex (more men than women), family history, diabetes, hypertension, and previous stroke, TIA, or heart attack. Many CABG patients have these risk factors.

The study reviewed data from 45,432 patients (average age, 63 years) who underwent primary or reoperative CABG surgery. Strokes occurring following CABG were recorded prospectively and classified as having occurred intraoperative or postoperatively. CABA operative strategies was also noted: 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).

Over the 30 years of this study, 705 patients (1.6%) experienced a stroke. Occurrence of stroke peaked in 1988 at 2.6%, then slowly declined by 4.69% per year. Of the 705 patients experiencing stroke, 279 (40%) occurred intraoperatively and 409 (58%) postoperatively. Timing of the stroke was undetermined in 17 patients.

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

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The ascending aorta is the site of surgical manipulations during CABG. Embolization of atherosclerotic debris is most likely to occur during aortic cannulation/decannulation, cross-clamp application/removal, and construction of proximal anastomoses.

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

Experiencing a stroke intra- or postoperative CABG substantially worsens 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%.

Patients who experience a stroke also experienced substantially longer intensive care unit and postoperative lengths of stay.

“Further studies are needed to develop better strategies to minimize the occurrence of stroke among patients undergoing CABG,” the researchers conclude.

Sources
Occurrence of Stroke After Coronary Artery Bypass Graft Surgery Appears To Be Decreasing; Tarakji KG, et al; JAMA 2011: Vol 305 (4)

Stroke during coronary bypass surgery: principal role of cerebral macroemboli; Eur J Cardiothorac Surg 2001;19:627-632; Michael A. Borger, Joan Ivanov, Richard D. Weisel, Vivek Rao, Charles M. Peniston

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