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Carotid Artery Stenting
definition
Carotid artery stenting (CAS) is an endovascular, Stent/catheter-based procedure which unblocks narrowings of the carotid artery lumen to prevent a stroke. Carotid artery stenosis can present with no symptoms (diagnosed incidentally) or with symptoms such as transient ischemic attacks (TIAs) or cerebrovascular accidents (CVAs, strokes). The largest clinical trial to date, CREST, compared stenting to surgery on the collective incidence of any stroke, any heart attack or death. They found that there was no significant differences out to four years of follow-up between surgery and carotid stenting when counting all three, but carotid endarterectomy (CEA) has a higher risk of heart attacks and CAS has a higher risk of minor stroke than open surgery. Overall, younger patients (<70 years old) had better outcomes with stenting than with surgery. Patients had fewer heart attacks with stenting, but they did have more minor strokes. There was no difference between surgery or stenting for major (disabling) strokes.
Prior to this, several European trials have reported results in symptomatic carotid artery stenosis patients comparing surgery and stenting. A major problem with the European tials is they allowed inexperienced operators to place stents, while the surgeons performing CEA were very experienced. The SPACE trial, conducted in Germany, Austria, and Switzerland found no difference in outcomes between surgery and stenting. They also noted that younger (< 67 years old) patients had better outcomes with stenting. They noted that more experienced centers had better results than inexperienced centers.
The EVA-3s trial was stopped early due to an early finding that stenting was too dangerous. The trial was criticized that they used experienced surgeons and inexperienced stent physicians, so that the results may have been affected by the training of operators. Future trials ensured that the endovascular arms had more experienced endovascular operators, as seen in the CREST and SAPPHIRE trial.
An interim report from ICSS demonstrates no overall difference between surgery and stenting for both major strokes and death, but again did show more minor strokes (resolved within 30 days) with stents and open surgery was safer than CAS in the treatment of symptomatic carotid artery disease. A study was carried out in seven of the centers participating in ICSS to assess the incidence of ischemic brain lesions (silent infarcts) detected by diffusion-weighted MRI. They found that 73% of patients undergoing CAS with distal filter protection showed new ischemic lesions after the procedure versus 17% of those undergoing CEA.
Recently physicians have questioned the ethics and validity of European trials comparing a mature carotid surgical procedure to carotid stenting performed by inexperienced physicians. In CREST, physicians performed procedures on a trial basis and were then permitted to enroll patients once their expertise in the carotid stent procedure could be confirmed. Conversely, some may wonder if it may be unethical to continue to perform stenting in all patients (instead of those who are at higher risk for surgery) in an effort to learn how to make a new technology functional.
Procedure
- Informed consent obtained and local anaesthetic administered
- Preparation of both groins with antiseptic and draped
- Puncture into femoral artery and access through short sheath
- Guidewire passed through aorta and into arch
- Arch aortogram obtained if not previously performed to confirm suitability to continue
- Carotid and cerebral angiogram performed
- Long access sheath placed after cannulation of common carotid artery (CCA)
- Guidewire passed through area of carotid narrowing
- Placement of embolic protection device above the area of narrowing
- Angioplasty of carotid narrowing, but more commonly proceed straight to deployment of stent into area of narrowing
- Angioplasty post stent deployment
- Removal of protection device, guidewires and sheath
- Aftercare of groin puncture site
Indications
Carotid stenting is the preferred therapy for patients who are at an increased risk with carotid surgery. High risk factors include medical comorbidities (severe heart disease, heart failure, severe lung disease, age > 75/80, etc) and anatomic features (contralateral carotid occlusion, radiation therapy to the neck, prior ipsilateral carotid artery surgery, intra-thoracic or intracranial carotid disease) that make surgery difficult or risky (1).
Anatomic high surgical risk: Contralateral carotid occlusion Contralateral laryngeal palsy Post-radiation treatment Previous CEA recurrent stenosis High cervical ICA lesions CCA lesions below the clavicle Severe tandem lesions
Co-morbid high surgical risk: Congestive Heart Failure (Class III/IV), and/or known severe left ventricular dysfunction <30% Open-heart surgery within 6 weeks Recent myocardial infarction (>24 hours and <4 weeks) Unstable angina (CCS class III/IV) Synchronous severe cardiac and carotid disease requiring open heart surgery and carotid revascularization Severe pulmonary disease to include any of the following: Chronic oxygen therapy Resting P02 of < 60 mmHg Baseline hematocrit > 50% FEV1 or DLCO < 50% of normal Abnormal stress test Age greater than 80 years
Using the criteria of successful trials, candidates are either symptomatic (TIA or stroke) patients with >50% stenosis of the carotid artery, or are asymptomatic with >80% stenosis of the internal carotid artery.
Carotid stenting may be considered an alternative to carotid surgery in average surgical risk patients, albeit with a higher risk of death or stroke as seen in the SAPPHIRE and CREST trials (2).
Features that favor carotid stenting include non-atherosclerotic cause of the stenosis (fibrodysplasia, radiation, early post-surgical stenosis or flap) an experienced center and experienced physician performing the procedure. Features that make stent placement more difficult include significant aortic arch tortuosity, thrombus containing lesions, occluded carotid artery, heavily calcified vessels, symptomatic patients and very tortuous and twisting vessels. None of these affect open, surgical endarterectomy.
Patient Selection Warnings
Lesion Characteristics: Patients with evidence of intraluminal thrombus thought to increase the risk of plaque fragmentation and distal embolization. Patients whose lesion(s) may require more than two stents. Patients with total occlusion of the target vessel. Patients with highly calcified lesions resistant to PTA. Concurrent treatment of bilateral lesions.
Access Characteristics: Patients with known peripheral vascular, supra-aortic or internal carotid artery tortuosity that would preclude the use of catheter-based techniques. Patients in whom femoral or brachial arterial access is not possible
Patient Characteristics: Patients experiencing acute ischemic neurologic stroke or who experienced a large stroke within 48 hours. Patients with an intracranial mass lesion (i.e., abscess, tumor, or infection) or aneurysm (>9mm). Patients with arterio-venous malformations of the territory of the target carotid artery. Patients with coagulopathies. Patients with poor renal function, who, in the physician’s opinion, may be at high-risk for a reaction to contrast medium. Pregnant patients or patients under the age of 18.
References
(1) Gurm HS, Yadav JS, Fayad P, Katzen BT, Mishkel GJ, Bajwa TK, Ansel G, Strickman NE, Wang H, Cohen SA, Massaro JM, Cutlip DE; SAPPHIRE Investigators. Long-term results of carotid stenting versus endarterectomy in high-risk patients. N Engl J Med. 2008 Apr 10;358(15):1572-9. PMID 18403765.
(2)Brott TG, Hobson RW 2nd, Howard G, Roubin GS, Clark WM, Brooks W, Mackey A,Hill MD, Leimgruber PP, Sheffet AJ, Howard VJ, Moore WS, Voeks JH, Hopkins LN, Cutlip DE, Cohen DJ, Popma JJ, Ferguson RD, Cohen SN, Blackshear JL, Silver FL, Mohr JP, Lal BK, Meschia JF; CREST Investigators. Stenting versus endarterectomy for treatment of carotid-artery stenosis. N Engl J Med. 2010 Jul 1;363(1):11-23. Epub 26 May 2010. PMID 20505173.
