Perioperative myocardial infarction caused by atheroembolism
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We have demonstrated a phenomenon occurring during coronary artery bypass grafting (CABG) which has not been previously described. Thirteen instances of fatal perioperative myocardial infarction following CABG were associated with intraoperative atheromatous embolization in the coronary microcirculation. In five cases the emboli originated from ulcerative atherosclerotic lesions in the aortic root at the site of the vein graft ostia; in two cases they likely emanated from coronary endarterectomy sites; and in two cases from mechanical disruption of plaques in the major epicardial coronary arteries during the operation. These nine cases occurred during initial revascularization procedures. We have performed 4,095 initial CABG procedures, and the nine cases represent a risk of 0.22%. A further four cases occurred during repeat CABG procedures and resulted from manipulative disruption of atheroma in old vein grafts. Our total number of repeat CABGs is 175, and the risk at reoperation is 2.29%; this represents a tenfold increase in risk for this complication at reoperation. Inadequate histologic sampling of the myocardium at autopsy will necessarily result in underestimation of the incidence of this phenomenon. Analysis of angiograms prior to repeat CABG can identify patients at increased risk who have severe graft atherosclerosis as opposed to myointimal hyperplasia. To reduce the incidence of atheroembolism at reoperation, we advocate ligation of the vein graft at the level of the distal anastomosis as early as possible during dissection on reopening the chest.
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