Carotid stenting

# Overview
Carotid stenting (CAS) is a percutaneous, endovascular procedure available to correct carotid stenosis (narrowing of the carotid artery lumen by atheroma).  Carotid stenosis can present with no symptoms (diagnosed incidentally) or through symptoms such as transient ischemic attacks (TIAs) or cerebrovascular accidents (CVAs, strokes).

# Landmark Studies
In a number of clinical trials, in patients at increased for carotid surgery, the rates of 30 day stroke and death have been noninferior or as good as  the standard approach, carotid endarterectomy.  Over 14,000 patients have been enrolled in trials to evaluate the results of carotid stenting in patients at increased-risk for surgery.  High-risk characteristics include anatomical or medical co-morbid conditions.  The most significant study to date has been the SAPPHIRE study, which in a randomized controlled study showed carotid stenting to be "noninferior" to endarterectomy in total Major Adverse Event rates, but superior in rates of major procedural stroke, cranial nerve palsy, and myocardial infarction. 
The question of carotid stenting in non-hi-risk patients has yet to be answered, with a few trials ongoing, including the Carotid Revsacularization Endarterectomy versus Stenting Trial (CREST) funded by the National Institutes of Health (NIH.)

# Indications
The aim of CAS is to prevent the adverse sequelae of carotid artery stenosis secondary to atherosclerotic disease, i.e. stroke.
Carotid stenting is currently indicated for the following patients:
Either
- Symptomatic patients with >50% stenosis
OR
- Asymptomatic patients with >80% stenosis
AND
- At least one anatomic or co-morbid risk factor placing them at high-risk for adverse events from CEA:
- Contralateral carotid artery occlusion
- Contralateral laryngeal nerve palsy
- Scarring of the neck post radiation therapy or following neck surgery
- Recurrent stenosis after prior carotid surgery
- High cervical carotid artery lesions
- Carotid artery stenosis:
Below the clavicle
Distal to the second cervical vertebra
Proximal (intrathoracic) arterial stenosis
- Below the clavicle
- Distal to the second cervical vertebra
- Proximal (intrathoracic) arterial stenosis
- Previous carotid endarterectomy
- Contralateral vocal cord paralysis
- Open tracheostomy
- Congestive Heart Failure (Class III/IV), and/or known severe left ventricular dysfunction 30%
- Open-heart surgery needed 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
- 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

### Carotid Revascularization in Patients Undergoing CABG
CAS (with embolic protection) before or concurrent with CABG is reasonable in patients with >80% stenosis who have experienced ipsilateral retinal or hemispheric cerebral ischemic symptoms within 6 months (I,C).
The safety and efficacy of carotid revascularization before or concurrent with myocardial revacularization are not well established (II b, C).

# Risk Stratification

## High Risk Lesion Characteristics
- Evidence of intraluminal thrombus thought to increase the risk of plaque fragmentation and distal embolization
- Lesion(s) that may require more than two stents
- Very tortuous lesions
- Total occlusion of the target vessel
- Lesions of the ostium of the common carotid
- Highly calcified lesions resistant to balloon inflation
- Concurrent treatment of bilateral lesions

## High Risk 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 access is not possible

## High Risk Patient Characteristics
- Patients at low-to-moderate risk for adverse events from carotid endarterectomy.
- Patients experiencing acute ischemic neurologic stroke or who experienced a 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 physicians opinion, may be at high-risk for a reaction to contrast medium.
- Patients with perforated vessels evidenced by extravasation of contrast media.
- Patients with aneurysmal dilation immediately proximal or distal to the lesion.
- Pregnant patients or patients under the age of 18.

# Stenting (CAS) vs Carotid Endarterectomy (CEA)

## Outcomes
- The CREST study showed a higher rate of death/MI in patients treated with stenting vs CEA: 6.4% vs 4.7%.

## Scenarios Where Carotid Endarterectomy is Preferred
Carotid endarterectomy is preferred in the setting of:
- Impaired renal function with increased risk of contrast induced nephropathy
- A tortuous calcified aortoa
- Complex, eccentric, calcified lesions

## Scenarios Where Carotid Endarterectomy is Preferred
Carotid endarterectomy is preferred in the setting of:
- Neck anatomy unfavorable for arterial surgery(II a, B)
- High carotid bifurcations where it is hard for surgeons to technically perform the surgery.
- Arterial stenosis distal to the second cervical vertebra or proximal (intrathoracic) arterial stenosis
- Previous ipsilateral carotid endarterectomy CEA
- Contralateral vocal cord paralysis
- Open tracheostomy
- History of previous radical neck surgery
- History of radiation therapy

# 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