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Ann Thorac Surg 1999;67:483
© 1999 The Society of Thoracic Surgeons
a Department of Thoracic and Cardiovascular Surgery, Lahey Clinic, 41 Mall Rd, Burlington, MA 01805, USA
e-mail: lars.g.svensson{at}lahey.org
Invited commentary
The causes of stroke after cardiac operations are multimodal and some of the more likely predisposing factors include older age, diabetes, female sex, left main coronary artery stenosis, poor ejection fraction, postinfarction angina or ventricular clot, a history of either stroke or neurologic events, peripheral vascular disease, carotid stenoses, smoking, hypertension, femoral arterial cannulation, ascending aortic cannulation, high systemic pressures or use of a side-biting clamp during aortic cannulation, prolonged cardiopulmonary bypass time, warm cardioplegia, possibly systemic normothermia, hypothermic circulatory arrest, excessive warming after coding, valvular or aortic operations, postoperative inotropic agents or balloon pump support, and postoperative atrial fibrillation. To this can be added the findings of Ura and colleagues of new intimal lesions, probably either lifted atheroma plaques or thrombus formation at the clamp and cannulation sites accounting for some delayed strokes.
Two comprehensive studies from the Cleveland Clinic and Brigham and Women’s Hospital have shown that single aortic cross-clamping for coronary artery revascularization operations reduces the risk of stroke when compared with the use of side-biting clamps for the proximal anastomosis. Of note, in this study by Ura and colleagues, the single patient who did have the use of a side-biting clamp experienced a stroke. Both of the remaining patients who had strokes related to single aortic cross-clamping also had severe grades of arteriosclerotic disease (grades 3 and 4). In the above situation, most surgeons would have advised a different approach in these patients with severe arteriosclerosis, such as either beating heart or fibrillatory arrest on pump, hypothermic circulatory arrest, or off-pump coronary artery bypass grafting. The authors, however, had 2 patients who experienced strokes after beating heart pump-supported coronary artery bypass graft surgery because of ventricular fibrillation and hypoperfusion. It is not clear whether ventricular fibrillation occurred during or after cardiopulmonary bypass, although if the patients were on cardiopulmonary bypass, hypotension should not have been a problem. How to establish cardiopulmonary bypass may also be a quandary in these patients because of plaque displacement or "jet" lesions forming at the cannulation site as the authors noted. Increasingly, in these types of situations where off-pump surgery is not feasible, I have found right subclavian artery cannulation to be of value, particularly as this can be combined with hypothermic fibrillatory cardiac arrest, without the need for aortic cross-clamping. Use of the right subclavian artery probably also reduces the risk of a jet lesion such as that observed in 2 patients of Ura and colleagues. Furthermore, if atheromatous material needs to be removed from the aorta, deep hypothermia can easily be established before circulatory arrest and after endarterectomy or repair, embolic material can be flushed out. Off-pump coronary artery bypass grafting is also an option in these patients providing a side-biting clamp is not used.
I favor the approach of routinely cannulating the lateral lesser curve of the aortic arch and single aortic cross-clamping, but when necessary, because of ascending aortic atheroma or calcification, using fibrillatory arrest or off-pump coronary artery bypass graft surgery. Using this approach in my last consecutive 700 coronary artery revascularization operations, the permanent neurologic rate was 0.8% (6 of 700, 3 died), transient events (including transient ischemic attacks) 0.6% (4 of 700), and the mortality rate 1.3% (9 of 700). The reason for cannulating the lesser curve of the aortic arch (as long as there is no detectable atheroma) is because this will probably result in any possible emboli going distally to the abdominal organs and lower extremity rather than going to the brain and causing a stroke. In fact, I observed in 2 of my patients distal embolization of the abdominal organs and peripheral vasculature and yet the patients experienced no strokes.
Clearly, not all strokes are preventable and the management of associated asymptomatic carotid artery disease is controversial. Our own prospective study of routine preoperative noninvasive carotid artery screening indicated that most patients with unilateral asymptomatic carotid artery disease with less than 90% stenosis could safely undergo operation without a carotid endarterectomy. Similarly, whether patients with postoperative atrial fibrillation should be more aggressively anticoagulated because of the increased risk of stroke remains to be established. These latter two areas still require further evaluation to try and further reduce the risk of stroke after cardiac operations.
Related Article
Ann. Thorac. Surg. 1999 67: 478-483.
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