Incorrect Shunt Placement Due to Anatomic Variations of the Aortic Arch During Carotid Endarterectomy: A Rare Cause of Perioperative Ischemia?

Abstract

To the Editor: Though shunt insertion limits interruption of blood flow during carotid thromboendarterectomy (CTEA), the procedure itself may provoke stroke, usually by air or plaque embolism (1). We report a previously undescribed potential cause of cerebral hypoperfusion during shunting: occlusion of the brachiocephalic trunk during left CTEA due to an anatomic aortic arch variation. A 71-yr-old woman underwent left CTEA under general anesthesia. Insertion of a right radial artery catheter was uneventful. After carotid artery cross-clamping and shunt insertion, we noted loss of the right radial pulse pressure. Her arterial blood pressure, assessed by an oscillometric blood pressure cuff placed on the left arm, remained unchanged. No compression or kinking of the catheter-tubing-transducer system was noticed, and fast-flushing did not show signs of under- or over-damping. Patch angioplasty was completed uneventfully, with normal electroencephalogram tracings. Immediately after shunt removal, her right arterial pressure regained its original shape and correlated with the values assessed by the cuff on the left arm. An anatomic variation of the aortic arch was suspected: subsequent postoperative magnetic resonance angiography confirmed the left common carotid emerging from the innominate trunk (Fig. 1). No postoperative neurological deficiency was noted.Figure 1.: MRA showing the left common carotid emerging from the brachiocephalic trunk. LCCA = left common carotid artery, BCT = brachiocephalic trunk, RCCA = right common carotid artery, RScA = right subclavian artery.Since up to 20% of patients present with aortic arch variation, unintentional occlusion of adjacent vessels and subsequent ischemia may occur during shunt procedures (2). Loss of radial pressure tracing demonstrated subobstruction of the right subclavian artery. We do not know whether the balloon was located in the subclavian artery or more proximal, in the brachiocephalic trunk. As no reflux of blood occurred in the operative field, occlusion of the brachiocephalic trunk seems more likely, potentially causing right cerebral hemisphere hypoperfusion in patients with inadequate redistribution of cerebral blood flow through the circle of Willis. To our knowledge, no case of stroke due to balloon obstruction of the opposite common carotid has been reported, and contralateral stroke remains exceptional. Indeed, during the North American Symptomatic Carotid Endarterectomy Trial (3), only one patient in 1415 awoke with a transient deficit in the contralateral carotid territory. Marc Koch, MD Marco Cristiani, MD Denis Schmartz, MD Department of Cardiothoracic and Vascular Anesthesiology Erasme University Hospital Free University of Brussels Brussels, Belgium [email protected]