Page 100 - Libro 2

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PART 2 — CEREBROVASCULAR
from the normalized internal carotid artery (ICA), through the bulb, and into the common carotid artery (CCA). The external carotid artery (ECA) is not nor- mally involved with significant disease, and therefore is typically not part of the procedure. Exposure is made sufficient to allow for the complete removal of the ath- eromatous material, which may extend from the distal CCA into the distal taper of the proximal ICA. Once the plaque is removed, the arteriotomy may be closed pri- marily by suturing together the cut edges of the arterial wall. In smaller diameter vessels, primary closure may narrow the lumen to the point of stenosis, particularly if the sutures are made deep to the incision.
Problems of stenosis associated with the CEA are more common at the distal border of the arteriotomy, where the ICA normalizes. At that point, common potential problems that may lead to a stenosis in- clude (1) narrowing as a result of closure; (2) plaque retained from an incomplete excision; and (3) a neointimal hyperplastic response to the operation, which occurs within subsequent months of follow- up. Of the three, only the latter can truly be charac- terized as a restenosis. Other forms of stenosis are caused by technical errors of the operation.
Because stenotic narrowing can result from clos- ing the arteriotomy primarily, surgeons will often re- duce the potential for stenosis by suturing in a patch to widen the lumen. The patch also reduces the po- tential intrusion a hyperplastic response that may develop a restenosis.1
SURGICAL PATCHES
The sonographer evaluating patients in follow-up to a CEA should expect to see patients with patches, particularly in female patients, whose arteries tend to be narrower than that of males. Patches for CEA may be either an autogenous vein or synthetic. The latter are constructed of either Dacron or polytetrafluoro- ethylene (PTFE). Veins used for the patch may be a cervical vein that is exposed and harvested from the incision site or a segment that is taken from the great saphenous vein at the ankle. Veins are often everted to create a patch with double wall thickness that will be stronger than the vein that is incised and flattened for a single wall patch. The vein is everted to allow the vein intima to face the lumen of the artery.1
EVERSION VERSUS TRADITIONAL CEA
In recent years, vascular surgeons are performing the operation using a technique called eversion CEA. The procedure, popular in Europe but less common in the United States, is receiving attention. Instead of using a long axis arteriotomy and patch, eversion CEA is performed with a complete transection of the
ICA at the bifurcation or of both the ICA and the ECA. An endarterectomy is performed by everting the cut ends of the arteries away from the incision and peeling the arterial wall away from the plaque as it is everted. The ends of the arteries are reverted to their normal position for subsequent reattachment. The procedure does not require a patch because the sutures are placed on the widened bulb of the ICA.2
To the vascular sonographer, the eversion CEA will be less obvious in its presentation than the tra- ditional CEA with patch. It will appear more like the traditional revascularization that was closed primarily (without a patch). Sutures, if visible, will surround the ICA circumferentially. In the standard CEA, the suture line will have an orientation along the long axis of the ICA, on its superficial wall. The eversion technique has the advantage of not requir- ing a patch because the full diameter of the distal taper of the ICA is retained and possibly enlarged in the process of feathering the plaque beyond the bulb. The sonographer should expect to see less restenosis in the eversion CEA than in the CEA with a primary closure, but eversion appears to have equivalent re- stenosis to the traditional CEA with a patch.2
SONOGRAPHIC EXAMINATION TECHNIQUES
Most follow-up evaluations arise as scheduled outpa- tient appointments. Emergent testing is infrequently requested in an immediate postoperative patient.
Patient Preparation
The CEA evaluation may be particularly difficult in the immediate postoperative period. Sutures, staples, and dressings all compromise access for the sonographer. Sterile techniques including sterile imaging pads, gel, transducer covers, or bio-occlusive dressings should be used to minimize the risk of infection when scan- ning a patient in the first 48 hours following surgery. Once the skin has healed, there is little impedance to the ultrasound examination. No specific preparation is typically required other than to remove jewelry or clothing that may limit access to the neck.
In the long term, patients with CEA should be fol- lowed with duplex ultrasound testing. For any follow- up protocol, it is important that the first duplex exam be performed within 1 month of the CEA. This serves as the baseline study that will provide the velocity data to which all subsequent follow-ups should be compared.
Patient Positioning
The patient should be positioned supine with a small pillow placed under the head and shoulders. The pa- tient’s chin should be tilted up and the head turned