Stroke is a major complication of cardiac surgery, with an incidence ranging from 2.1 to 5.2 percent. As many as 22 percent of coronary artery bypass graft (CABG) candidates have hemodynamically significant carotid disease, which is a risk factor for perioperative stroke. This percentage is likely to increase as the population continues to age and CABG is used in increasingly older patients. Although carotid disease is associated with an increase in perioperative stroke risk, it is responsible for only a minority of strokes associated with CABG. In addition, it is important to note that carotid stenosis has never been shown to be an independent risk factor for perioperative stroke while controlling for aortic arch atherosclerosis.
Several mechanisms have been proposed for perioperative strokes after CABG; the most important are arterial emboli and cerebral hypoperfusion. It is theoretically possible for carotid lesions to act through either mechanism, showering emboli through plaque rupture or causing hypoperfusion via thrombosis and/or obstruction of arterial flow. However, the perioperative stroke risk associated with carotid stenosis may also be related to emboli originating from aortic arch atheromas.
On physical examination, the most important finding is the presence of a carotid bruit. Although a carotid bruit is not pathognomonic for carotid stenosis, studies at the Johns Hopkins Hospital suggest a 40-percent positive predictive value for carotid stenosis (in excess of 70 percent) in CABG populations. From a demographic perspective, increased age, cerebrovascular disease (CVD), and peripheral vascular disease also greatly increase the likelihood of carotid disease. For patients at risk for carotid disease, duplex ultrasound represents a noninvasive means of assessing carotid disease quantitatively. Magnetic resonance angiography, cerebral angiography, and computed tomography (CT)–angiography represent more costly and/or invasive methods of assessing the degree of stenosis that may be useful in confirming duplex findings and in instances in which duplex results are indeterminate.
Treatment of patients with combined coronary and carotid disease centers on medical management with antiplatelet therapy and/or cholesterol-lowering agents and carotid endarterectomy (CEA). Patients who are candidates for CABG and in whom CEA also is indicated can be approached with one of three strategies: “staged” but separate procedures with CEA performed before CABG, the “combined” procedure with CEA and CABG performed under the same anesthesia, and “reverse-staged” procedures with CABG performed before CEA. In their practice, the authors advocate treating the symptomatic territory (i.e., carotid or coronary) first and reserving combined procedures for patients with severe symptoms in both territories. Percutaneous carotid angioplasty with or without stenting is an emerging technique that is being applied in concert with CABG in a similar fashion at select centers.
In the absence of large prospective randomized trials, there is no high-grade evidence to support the contention that CEA lowers perioperative stroke risk in the context of CABG. However, the most recent meta-analyses indicate that myocardial infarction (MI) is more common in patients undergoing the staged procedure and stroke rates are higher in those undergoing ...
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