rel="nofollow" href="#fb3_img_img_6490c939-e834-5df3-98e5-854c43951ec0.jpg" alt=""/> Duplex ultrasonography to exclude fresh thrombus formation
Peri-interventional therapy
Technique of carotid artery stenting (CAS)
Access route
It is important to establish a safe vascular access route in order to minimize complications during carotid stent implantation, and access via the femoral artery is the approach most often employed. The common femoral artery is punctured using a Seldinger needle, and a 12-cm long 5–6F sheath is placed. This initial sheath is then exchanged during the procedure for a 90-cm long sheath (e.g., Cook Shuttle sheath.). If a guiding catheter is to be used, a 12-cm long 8–9F sheath is needed. In patients in whom the pelvic arteries are occluded or who have high-grade stenosis, or in situations in which the access route via the femoral artery is unavailable for other reasons, access via the brachial or radial artery is obtained (Fig. 1.1-11). The right brachial artery is preferable for interventions on both the right internal carotid artery and the left internal carotid artery. If neither access route is possible, direct cervical common carotid access (percutaneous or open surgical) can be considered.
Engaging the common carotid artery
Angiography of the aortic arch is generally performed prior to any selective carotid angiography in order to identify possible difficult anatomic conditions that might make it necessary to exchange the typically employed diagnostic catheters (e.g., Berenstein, Judkins Right, Head Hunter, IMA, JB-1) for an alternative one (e.g., Simmons or Vitek catheter) (Fig. 1.1-12). To engage the common carotid artery, the 5F diagnostic catheter (e.g., Berenstein, Right Judkins, Head Hunter, IMA) is positioned over a 0.035-inch hydrophilic guidewire in the ascending aorta with the catheter tip pointing downward. This technique reduces the likelihood of embolization from aortic plaque or traumatic injury to the intima of the aortic arch and prevents the catheter from becoming caught in a vascular ostium. As soon as the catheter reaches the ascending aorta, it is rotated 180°. This places the tip of the catheter in a vertical, upright position on fluoroscopy. The catheter is then carefully withdrawn until it slides into the brachiocephalic trunk, and the hydrophilic wire is then advanced into the right common carotid artery and the catheter is advanced over this wire into the common carotid artery. To intubate the left common carotid artery, the catheter is slowly withdrawn from the ostium of the brachiocephalic trunk. It should be rotated 20° counterclockwise, so that the catheter tip points slightly anteriorly. When the aortic arch becomes unwound with advancing age, the origin of the left common carotid artery is located slightly further posterior. In these cases, it may be necessary to rotate the catheter posteriorly instead.
Fig. 1.1–11a, b Access via the brachial artery.
Fig. 1.1–12a, b (a) Simple anatomic conditions. (b) More difficult anatomic conditions. The catheter is capable of prolapsing into the ascending aorta.
Once the left common carotid artery has been entered, the catheter should be rotated back 20° clockwise, so that the tip is once again pointing vertically or slightly posteriorly. The catheter position is checked by administering a small amount of contrast. This can exclude subintimal contrast flow or reduced blood flow. The hydrophilic wire is advanced to the distal common carotid artery, followed by the catheter.
Exploring the common carotid artery in difficult anatomy
If engagement of the common carotid artery is unsuccessful with the standard catheter, then a switch to a Simmons catheter is usually made. This type of catheter has a large reverse curve which must be re-shaped in the aorta after wire removal, usually in the ascending aorta. Moving the catheter backward slightly guides the tip into the brachiocephalic trunk, then into the left common carotid artery, and finally into the left subclavian artery. In contrast, Vitek or Mani catheters have smaller pre-formed curves and do not require shaping so these catheters are advanced from, rather than withdrawn toward, the distal aortic arch selecting the left subclavian artery first, and so on. Once the desired vessel is selected, the wire is advanced followed by the catheter. Advancement of the catheter is carried out slowly and with assistance from the pulsating blood flow. At the same time, the wire is withdrawn slightly, so that its position is maintained proximal to the carotid bifurcation. Advancement of the catheter and withdrawal of the guidewire are carried out alternately several times until the catheter is safely positioned in the vessel (push-and-pull technique) (Fig. 1.1-13).
Fig. 1.1–13a, b The push-and-pull technique.
Visualizing the vessels
Injections of contrast medium should be carried out manually or with a small amount of automated contrast administration (a maximum of 6 mL per injection). Larger amounts would lead to mixing of the arterial, intermediate, and venous phases, potentially leading to masking of early venous filling or other types of pathology. Some operators carry out four-vessel angiography to show the status of the collateral arteries. However, as this represents an additional procedural risk, the need for it is questionable, particularly in patients in whom magnetic resonance angiography has previously been carried out. During balloon dilation, the absence of collaterals may cause short periods of cerebral ischemia due to brief occlusion of the internal carotid artery. However, this reaction is reversible after deflation of the balloon and has no influence on the completion of the procedure. Once the anatomy of the target vessel has been defined, a hydrophilic guidewire is advanced into the external carotid artery so that the diagnostic catheter can be exchanged for a sheath or guide sheath. Bony landmarks can be used for guidance instead of road mapping to mark the origin of the external carotid artery during wire placement.
Vascular kinking
If
