Carotid Interventions

From Stroke Education
Jump to: navigation, search

Learning objectives

  • Appropriate screening for carotid disease
  • Preventative Role of Carotid Endarterectomy and Stenting
  • Evidence base for selection
  • Appropriateness of referrals
  • Post op complications

Carotid Endarterectomy (CEA) to prevent Stroke

Carotid endarterectomy is an operation that has been done for decades and it was the two trials NASCET[1] (North American Symptomatic CEA Trial) and ECST [3] (European Carotid Surgery Trial) which help to set the current terms on which surgery is now performed showing benefit above best medical therapy for these with more than 50% stenosis. A further trial ACAS (Asymptomatic Carotid artery study) showed lesser benefit in asymptomatic patients. At the time of the NASCET and ECST trials, usual practice was to defer CEA for 4 to 6 weeks after a stroke in an effort to reduce the complication of a postoperative haemor­rhagic transformation of a bland infarction. Such delays are not recommended in current guidelines.

In terms of asymptomatic disease there is a huge divide between UK and US practice as most CEA done in the US are on asymptomatic patients where the risks and benefits are very finely matched, whereas in the UK there is a clear policy to avoid surgery on asymptomatic patients and offer best medical therapy. Another point is that these carotid trials are from the 1990s and may not reflect current best medical therapies especially regarding optimal statin usage, the use of newer antiplatelets and now better control of blood pressure and smoking cessation. So, despite a large body of evidence on the role of CEA there is still disagreement about the indications for carotid intervention to prevent stroke for a number of patients.

The concept of the surgery is to simply removing stenosing and possible “vulnerable" or "unstable" plaque which limits cerebral perfusion and can ulcerate or rupture leading to thrombosis and total or subtotal vessel occlusion or lead to thromboembolism to brain. What has become more apparent is that we find more and more patients with evidence of prior total occlusion of internal carotid arteries with no evidence of any neurological sequela. If there is a gradual slow occlusion if the ICA then perhaps collateralisation over time can be protective.

CEA is for those with anterior circulation TIA or non disabling anterior circulation stroke and should be done on those with a symptomatic stenosis of > 50-70%. The Doppler will show high velocities which generate turbulence and embolic stroke disease. The atherosclerotic stenosing plaque can also become unstable and ulcerate or rupture and cause total occlusion. There is nothing to be done once the vessel is totally occluded as the damage is done. It is surprising that patients can have asymptomatic complete occlusion of one or other carotid. The surgery should be done within days but definitely less than 2 weeks. Treat as a vascular emergency. Surgical expertise and general surgical care are important.

Carotid angioplasty and stenting is much talked about as an alternative to CEA, and although attractive in concept the current evidence has not shown it to be superior to CEA and possibly to have higher complications. There is some benefit of surgery for 50-70% stenosis, except in women and those with ocular events. The benefit of surgery is modest in patients with ocular events, lacunar infarcts, contralateral carotid occlusion, and with collapse of the vessel distal to very severe stenosis. The benefit of surgery is greatest within days of the relevant cerebrovascular event and declines rapidly over time, so that it is minimal after 3-6 months. There is little benefit for surgery in patients with asymptomatic carotid stenosis

Clinical

  • Transient monocular blindness, Embolic stroke in anterior circulation
  • Watershed infarction, Audible Carotid bruit
  • Hypertension, smoker, dyslipidaemia

Investigations

General advice is that one should not perform carotid intervention on the basis of stenosis documented by a single modality. Although USS Doppler is the current recommendation this should be followed by either MRA or CTA in those planned for surgery to reassess risks and ensure there has been correct risk stratification on the basis of stenosis. It is well recognised that different operators make a subjective difference in the outcome of such assessments and much is operator dependent especially in borderline cases. Rather than a different modality some opt to repeat the Doppler. Carotid duplex showing a peak systolic velocity of > 129 cm/sec correlates well with stenosis over 70%. Care must be taken with CTA and MRA as they can sometimes overstate stenosis. The gold standard is angiography but this has stroke and other risks and is not practicable in many centres. The second modality recommendation is ignored in many centres and is often used in a more focused way to further review borderlines cases. The concerns are often that further screening by other imaging modalities may ultimately delay surgery.

Secondary prevention of stroke with carotid surgery

Severity of stenosisRelative risk reduction Absolute risk reductionNumber-needed-to-operate to prevent one stroke in 2 years
OccludedNot for SurgeryNot for SurgeryNot for Surgery
Symptomatic (70-99%)65%13%8%
Symptomatic (50-69%)30%7%14%
Symptomatic (< 50%)No benefitNo benefitNo benefit

Complications

  • Stroke: there is a chance that surgery can lead to thrombus in situ around the area of the surgery and ipsilateral thrombotic or embolic stroke.
  • Reperfusion syndrome: Relief of stenosis can cause a hyperperfusion syndrome with oedema on the ipsilateral affected side and this can precipitate weakness and a stroke like presentation.
  • Perioperative bleeding, Cranial Nerve Injury
  • Perioperative MI, Pneumonia, Death

Management

All patients with proven carotid disease should have best medical therapy in terms of management of atherosclerotic disease including antiplatelets, hypertension control, high dose statin and smoking cessation and exercise. As can be seen from the trials below they were published in the early 1990s and reflect patients treated and recruited through the 1980s before near ubiquitous prescribing of statins. Intervention must be on a background of medical therapies which are proven and safe. Another note is that carotid disease is a strong pointer of coronary artery disease and best medical therapy will be managing this risk too. CEA should only be offered to those with symptomatic disease clearly attributable only to an ipsilateral stenosing lesion. The most important indicator of future stroke risk is the pres­ence of recent symptoms. There is an ever decreasing benefit from surgery the further one is from the prime event. Where there are confounding risks e.g. coexisting AF which could account for symptoms in a patient with a mild stenosis then a more circumspect degree of risk hedging may be appropriate as any potential gain may be diluted by a lack of diagnostic uncertainty as to aetiology.

Carotid Artery Stenting (CAS) as an alternative to surgery seems attractive but has not proven itself as the standard of care and ongoing research continues. CEA remains the gold standard for carotid intervention It can be justified for patients whose medical comorbidities or cervical anatomy make them questionable candidates for CEA. Previous neck surgery or irradiation may increase surgical complexity. CAS should be reserved for symptomatic patients with stenosis 50-99% at high risk for CEA and is not recommended for asymptomatic patients. SAPPHIRE [7] was an underpowered study that looked at CAS versus CEA with no proven benefits shown over CEA. CREST was a further study that favoured CEA and showed that CAS was associated with neurological events [5] and with increased complications in octogenarians [6].

Summary of National Guidance

General Accepted Pooling of National Guidance [8]
1. Symptomatic patients with angiographic stenosis of less than 50% and asymptomatic patients with ste­nosis of less than 60% should not undergo interven­tion and are best treated by BMT.
2. The particulars of medical therapy include control of comorbid conditions, risk reduction with anti­platelet therapy, statins, and beta blockade as indicated.
3. CEA is preferred over CAS in symptomatic patients with stenosis of more than 50% unless there are contraindications to CEA, such as uncompensated cardiac disease or local scarring that increase the risk of cranial nerve complication. The greater the degree of stenosis, the stronger the indication for intervention.
4. In symptomatic patients with stenosis of more than 50% who are at high risk for CEA, CAS is preferred over BMT. The greater the degree of stenosis, the stronger the indication for intervention.
5. In patients with stroke or TIA, intervention should be performed within 2 weeks unless there are con­traindications to intervention.
6. In good risk patients with asymptomatic stenosis of more than 60%, CEA may be recommended in addition to BMT for reduction of stroke risk as long as the combined stroke and death rates are less than 3%.
7. In asymptomatic patients at high risk for interven­tion, neither CAS nor CEA has been proven supe­rior to BMT.
8. Intervention is not indicated for patients with chronic total occlusion of the internal carotid artery or with severe disability that precludes preservation of useful function.

References

  • 1. North American Symptomatic Carotid Endarterectomy Trial Collabo­rators (NASCET): Beneficial effect of carotid endarterectomy in symptomatic patients with high-grade carotid stenosis. N Engl J Med 325:445-453, 1991.
  • 2. Barnett HJ, et al: Benefit of carotid endarterectomy in patients with symptomatic moderate or severe stenosis. North American Symptom­atic Carotid Endarterectomy Trial Collaborators. N Engl J Med 339(20):1415-1425, 1998.
  • 3. Randomized trial of endarterectomy for recently symptomatic carotid stenosis: final results of the MRC European Carotid Surgery Trial (ECST). Lancet 351(9113):1379-1387, 1998.
  • 4. ACST Collaborators Group: The International Asymptomatic Carotid Surgery Trial (ACST). Lancet 363:1491-1502, 2004.
  • 5. Voeks JH, et al: CREST Investigators: Age and outcomes after carotid stenting and endarterectomy: the carotid revascularization endarterec­tomy versus stenting trial. Stroke 42:3484-3490, 2011.
  • 6. Hobson RW, 2nd, et al: CREST Investigators: Carotid artery stenting is associated with increased complications in octogenarians: 30-day stroke and death rates in the CREST lead-in phase. J Vasc Surg 40:1106-1111, 2004.
  • 7. Yadav JS, et al: Protected carotid artery stenting versus endarterectomy in high-risk patients. N Engl J Med 351:1493-1501, 2004
  • 8. Ricotta A et al. Rutherford's Vascular Surgery. pp 1510 Section 17 Cerebrovascular Diseases