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 the vessel is very tortuous, it can be straightened using a wire. It is also helpful to ask the patient to inhale deeply and hold the breath. An acute vessel angle can be negotiated by careful rotation and advancement of the catheter until it has reached the desired position (Fig. 1.1-14). If it is still not possible to advance the catheter, a Simmons III catheter should be used to introduce the guidewire into the external carotid artery. The Simmons III catheter can then be exchanged for a 4F multipurpose catheter. After this, the hydrophilic wire is exchanged for a 0.035-inch Amplatz wire or a softer wire. Finally, the 4F catheter is exchanged for a 5F catheter.
Fig. 1.1–14a-c (a) The technique of probing the left common carotid artery (CCA) and placing the guidewire in the external carotid artery (ECA) in the presence of a common trunk. (b) Placement of an IMA diagnostic catheter at the origin of the CCA. (c) Probing the ECA with a 0.035” wire with antifriction coating (Terumo) and advancing the diagnostic catheter with slight right–left rotation as far as the ECA. Replacement with a more rigid uncoated wire (e.g., Supracor).
Placement of the guiding catheter
An 8F guiding catheter (e.g., a right coronary guiding catheter) is introduced into the ascending aorta via a hydrophilic 0.035-inch wire. In cases of difficult or abnormal anatomy, aortography of the aortic arch can be used to assist in selective exploration. Following angiography of the aortic arch and assessment of the anatomy, the guiding catheter is introduced into the common carotid artery. This should be followed by careful aspiration and flushing with saline to clear any possible atherosclerotic particles out of the catheter.
Placement of the long sheath
Engagement of the common carotid artery is carried out with a 5F diagnostic catheter and access to the external carotid artery obtained with an angled hydrophilic guidewire, and the diagnostic catheter introduced into the external carotid artery as described above. The wire is exchanged for a 0.035-inch wire, typically a stiff Amplatz wire. The diagnostic catheter is removed and a 6F 90-cm sheath placed using an over-the-wire technique into the common carotid artery below the bifurcation. The sheath should be handled very carefully, as trauma to the common carotid artery ostium or release of atherosclerotic deposits may occur leading to neurologic sequelae. The sheath should be meticulously aspirated and flushed to eliminate possible air or atherosclerotic debris.
Carotid access in occluded external carotid artery or common carotid artery stenosis
When the external carotid artery is occluded, or there is significant stenosis below the bifurcation, or a stenosis at the ostium of the common carotid artery, placing the 6F 90-cm sheath in the common carotid artery may represent a considerable challenge. If possible, crossing the stenosis with a stiff wire should be avoided, as this may dislodge necrotic plaque material and cause distal embolization. If necessary, the 5F diagnostic catheter is advanced over a 0.035- or 0.038-inch guidewire for placement further distally, slightly proximal to the stenosis. It can then be exchanged over a 0.035-inch Amplatz wire (extra stiff). If there is an ostial/proximal stenosis of the common carotid artery, it may be necessary to treat this stenosis first in order to obtain access to the distal stenosis. However, if this stenosis is not severe, the bifurcation stenosis should be treated first and then the proximal stenosis on the “way back.”
Predilation
Some operators predilate the stenosis using a small angioplasty balloon and a short inflation time of 5–10 seconds. This provides for better passage and positioning of the stent. The present authors would only recommend predilation if primary stent implantation has failed. In our view, primary stent implantation has a protective effect against distal embolization by fixing deposits on the vascular wall.
Protection against emboli
The possibility of procedural cerebral embolization is an important concern in carotid angioplasty. Balloon dilation, stent implantation, and manipulation of the vessels by the catheter and wire can easily release emboli, which if large enough can in turn cause severe cerebral damage. For this reason, emboli protection systems are routinely used in most centers. There are currently three different underlying principles on which protection against cerebral embolism is based: filter systems, distal occlusion balloons, and proximal occlusion balloons.
Distal occlusion balloons
Distal occlusion balloons (Fig. 1.1-15a) were the first embolism protection systems to become available, and were widely used in the initial carotid stent experience. It consists of a 0.014-inch guidewire with an occlusion balloon in the distal section, which is inflated and deflated through a very small channel in the guiding catheter (Guardwire® Temporary Occlusion and Aspiration System, Medtronic Vascular; TriActiv® ProGuard™ Embolic Protection System, Kensey Nash). After the guiding catheter is placed, the occlusion balloon is positioned distal to the stenosis and the balloon inflated until blood flow into the internal carotid artery stops. Stent implantation then follows. After the intervention, an aspiration catheter is introduced up to the occlusion balloon, and the blood in the occluded artery is aspirated. Any particles released during the intervention are thus removed. The advantages of the distal occlusion system are its low profile (2.2F), flexibility and good steerability. Disadvantages include the fact that balloon occlusion is not tolerated in 6–10% of patients, and that the vascular segment distal to the occlusion balloon cannot be imaged using contrast during the balloon occlusion procedure.