Carotid Artery Stenting
Figure 2: Severe Stenosis of the Right Internal Carotid Artery – Filter and Stent Deployment
internal carotid artery (ICA) and emboli are captured and removed together with the device. Balloon occlusion devices and proximal protection systems completely occlude the flow into the ICA and emboli must be aspirated before balloon deflation or catheter removal.
Distal Occlusion Balloons
After direct catheterisation of the right common carotid artery using a 7Fr guiding catheter, a filter embolic protection (Angioguard™ 6mm) was advanced and released in a healthy tract of the internal carotid artery. A stent (Precise® 8x30mm) was deployed at the level of the stenotic tract landing into the common carotid artery. Post-dilation was performed using a 6mm low-profile balloon.
Figure 3: Severe Stenosis of the Right Internal Carotid Artery – Final Result
Distal occlusion balloons represent the first CPD routinely used in clinical practice. They consist of a 0.014-inch guidewire equipped with a distal balloon inflated through a small channel present within the wire. Once the lesion is crossed with the guidewire, the balloon is positioned above the lesion and inflated to completely occlude the ICA, thus avoiding the passage of micro-emboli into the intracranial circulation. After treatment of the lesion with angioplasty and stenting, a guiding catheter is advanced up to the balloon to aspirate the blood, possibly containing the debris dislodged from the atheroma. After complete aspiration of the blood present in the ICA, the balloon is deflated and the guidewire removed. The advantages of this system are represented by the very low profile of the balloon-wire crossing the lesion (≤2.2Fr) associated with the very high flexibility and torque of the system.15
On the other hand, the system
produces complete occlusion of the ICA and this haemodynamic condition cannot be well tolerated by 6–10% of patients.16
Moreover,
it is not possible to obtain continuous visualisation of the lesion during the procedure as the blood flow is completely blocked and contrast media injection is not possible.
Filters
The final angiogram showed a complete resolution of the stenosis with a residual stenosis
3.8 to 1.2%).11 Moreover, Kastrup et al.12 performed a cumulative
review of the most relevant publications between 1990 and 2002, comparing 2,537 unprotected CAS with 896 CAS performed using CPDs. The combined stroke and death rate within 30 days in both symptomatic and asymptomatic patients was higher in the group of patients treated without a CPD: 5.5% compared with 1.8% of the protected group (p
CPDs can be divided into three different types according to technical aspects: distal occlusion balloons, filters and proximal protection systems. Using filter systems, blood flow is maintained through the
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Filters consist of a metallic structure coated with a membrane made of polyethylene. The membrane of the filters may have different shapes and presents several pores with a diameter ranging from 80 to 220μm. Filters are mounted on a 0.014-inch guidewire, are generally 30mm proximal to a flexible tip and are delivered through a very-small-profile catheter (≤3Fr). Once the lesion is crossed, the filter should be opened in a straight portion of the ICA at least 2cm above the lesion. At the end of the stenting procedure, a retrieval catheter is inserted to re-capture the filter and remove it. In cases of very tight stenosis or very tortuous anatomy, the passage of the delivery catheter through the lesion may be difficult or impossible. In such cases, pre-dilation of the stenosis must be performed using a very small (2–3mm) balloon to avoid fracturing the plaque or stimulating the vagal sinux reflex. The diameter of the filter must be selected according to the calibre of the ICA segment where the filter will be placed. Generally, a filter diameter 1mm larger than the size of the artery is required to obtain correct wall apposition of the filter, reducing the possibility of failure to capture the emboli. As filters produce a marked reduction of the blood flow within the ICA, they should not be left in place for more than 15 minutes. Different types of distal filter are available on the market and others will appear in the future. Filters differ in terms of the rigidity of the metallic structure, the diameter of the pores and wire stiffness. A detailed knowledge of the technical characteristics of the various filters is essential for selecting the correct device on the basis of patient characteristics and avoiding any complications (see Figures 1–5).
Proximal Protection Systems
Distal occlusion balloons and filters have the disadvantage that the stenotic lesion must be crossed in order to place the device. This manoeuvre carries the risk of complete lumen occlusion and distal embolisation, especially in cases of unstable and complex plaques (ulcer, fresh thrombus). By contrast, proximal protection systems provide cerebral protection without the need to advance any type of
INTERVENTIONAL CARDIOLOGY
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