Vascular

Stenting of the carotid arteryM N s Hamady

Nicholas J W cheshire

AbstractThis contribution outlines the basic concepts underpinning stenting of

the carotid artery.

Keywords caVTas; saPPHIrE; stenting; distal protection device;

catheterization

Atherosclerosis of the carotid artery accounts for >35% of strokes. Carotid surgery is the first-line treatment for stroke prevention in patients with high-grade stenosis of the internal carotid artery. Balloon angioplasty of the carotid arteries has been carried out in significant numbers only during the last decade. The mod-ern procedure uses a stent specifically designed for the internal carotid artery and a distal protection device (Figure 1a and b).

Stenting or surgery?

Carotid artery stenting may replace carotid endarterectomy in the treatment of carotid disease. Several prospective random-ized controlled clinical trials comparing stenting and surgery are in progress across Europe and the USA. Single-centre case series (level-2 and level-3 evidence) must be analysed until these studies report; two randomized clinical trials have already reported.

Carotid Artery and Vertebral Artery Transluminal Angioplasty and Stenting (CAVATAS) studyThe overall rate of peri-procedural neurological events (includ-ing transient ischaemic accidents, minor and recovered strokes, major strokes) in >500 symptomatic patients randomized to carotid artery stenting or surgery was identical in both groups (about 10%). This finding was challenged by many surgeons because they do not observe such high rates of events in their own practice. Not all surgeons incorporate neurology review after surgery, and reported event rates are higher when a

This article was first published in Surgery 2004; 22(11): 283–4.

M N S Hamady FRCR is a Consultant Interventional Radiologist at

St Mary’s Hospital, London, UK. Conflicts of interest: none declared.

Nicholas J W Cheshire FRCS is a Professor of Vascular Surgery and

Associate Medical Director at St Mary’s Hospital, London, UK. Conflicts

of interest: none declared.

surGErY 25:8 35

neurologist is included in a carotid study. Death and disabling stroke in both arms of CAVATAS was also similar (5.8% for surgery; 6.5% for stenting). These figures more closely repre-sent those associated with the large clinical trials of surgery versus best medical therapy undertaken in Europe (ECST) and the USA (NASCET); event rates associated with surgery were 7.5% and 5.8%, respectively. Event rates for these stud-ies include all recorded events (rather than death and major stroke). Recruitment into CAVATAS began in 1992 and, over-all, only 1 in 4 patients in the endoluminal arm had a stent (the remainder underwent balloon dilation only). Addition of a carotid-specific stent and a distal protection device to the carotid artery stenting procedure can reduce the neurological event rate by up to 50%. A major limitation of the data from the endoluminal arm of the CAVATAS study is that it does not reflect the modern procedure of carotid artery stenting and therefore outcome.

Study of Angioplasty with Protection in Patients at High Risk for Endarterectomy (SAPPHIRE) studyThe SAPPHIRE study involved >300 patients at high risk for surgery due to cardiovascular or neck disease. Two-thirds of patients were asymptomatic with stenosis of the internal carotid artery of >80%. Findings suggest that carotid artery stenting may be safer than surgery in this subgroup. Immediate peri-operative neurological and cardiological complication rates were significantly fewer (5.8%) in carotid artery stenting compared with surgery (12.6%). At one year, the rate of major adverse events for carotid endarterectomy was 20.1%, and for carotid artery stenting was 12%.

The SAPPHIRE study used a combined endpoint of neurologi-cal and cardiological morbidity, but this may be reasonable for this particlular group of patients. The rates of death and major stroke in the SAPPHIRE study (about 3%) accord closely with the figures in the registry of the Vascular Society of Great Britain and Ireland. The registry shows that death and peri-procedural stroke in patients aged >80 years (one of the criteria for high risk) approaches 7%; data for myocardial events are not available.

Imaging

The approach to the carotid artery (access through the femoral and iliac arteries, crossing the aortic arch and entering the ori-gin of the common carotid artery) and the lesion in the internal carotid artery itself must be assessed. Severe atherosclerotic dis-ease or tortuosity in the approach vessels may increase risk or make the procedure impossible. Kinked and distorted internal carotid arteries with very tight (>95%) lesions containing soft, ulcerated plaque may be associated with higher rates of peri-procedural events.

Digital subtraction angiography is the first-line method to assess occlusive carotid disease. Magnetic resonance angio-graphy and/or CT angiography will replace digital subtraction angiography in the evaluation of extracranial carotid disease (as well as the intracranial circulation). Magnetic resonance angio-graphy and CT angiography are usually combined with colour Doppler ultrasound; the latter cannot assess the origin of the great arteries at the level of the arch or vessels at the circle of Willis.

4 © 2007 Published by Elsevier ltd.

Vascular

a angiogram of the left common carotid artery showing 80% stenosis at the origin of the internal carotid artery (arrow). b angiographic

appearance after stenting and balloon angioplasty of the left internal carotid artery (arrow). residual stenosis is absent.

Figure 1

Distal protection devices

Distal protection devices protect the intracranial circulation from distal embolization and there are two basic designs: • balloon occlusion systems • polyurethane sacs containing fine (a diameter of about

100 micron) pores.The distal protection device must cross the stenosis in the

internal carotid artery before it can be deployed; the characteris-tics and diameter of the delivery system are very demanding. The balloon-based systems have advantages for crossing the carotid lesion, whereas the sac devices are easier to close and ensure embolic debris is removed from the artery. The balloon occlusion systems require a patent carotid system on the opposite side and a functioning circle of Willis.

surGErY 25:8 35

Procedure

Carotid artery stenting involves selective catheterization of the common carotid artery using a fine catheter and wire. The wire is advanced into the external carotid artery. A larger sheath (7 F; diameter ≈2.5 mm) is parked in the normal segment of the com-mon carotid artery. The stenotic lesion in the internal carotid artery is negotiated with a distal protection device. This device is positioned in the distal internal carotid artery, proximal to the cavernous portion. Most operators carry out predilation with a 2–3 mm angioplasty balloon to ease introduction of the stent. A stent of appropriate size is then deployed. Further dilation from within the stent can be done as needed. The protection device is retrieved using a special sheath. Haemostasis is achieved by a percutaneous femoral artery closure device. ◆

5 © 2007 Published by Elsevier ltd.