Carotid Artery Stenosis: Surgery or Stent?

Case Presentation

Mr. AS is a 68 y/o AAM who presents to his primary care physician (PCP) for his annual routine checkup. He has a past medical history (PMH) of HTN, HLD, and a 50-pack year of tobacco smoking. He drinks a couple of times a week, especially when he “plays poker with the fellas”, and an unrestricted diet. During his exam his PCP detects a moderate to severe bruit on the left side. Mr. AS’ physician is concerned and decides to send him for a carotid ultrasound (U/S) right then and asks him to return to clinic once the U/S is complete.

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The ultrasound done in the outpatient clinic revealed a 60% stenosis at the bifurcation of the left internal/external carotid artery. An appointment was scheduled for the following day at the vascular surgeon’s office to assess the need for intervention and revascularization. At the appointment the vascular surgeon also detects a bruit on auscultation. The patient denies any history of focal neurologic symptoms but does admit to some lightheadedness and dizziness on occasion that he attributes to “just getting older”. The vascular surgeon prefers his own in-office sonographer and therefore, repeats the carotid U/S, which more accurately reveals an 80% stenotic lesion of the left carotid artery.

Introduction

Carotid artery stenosis is one of the most common causes of ischemic stroke (CVA) and transient ischemic attacks (TIA).1 The incidence of stroke becomes considerably increased with the extent of artery stenosis.1 Over the last 10 years there have been many significant improvements in how we care for patients with internal carotid artery (ICA) stenosis.1-3 The improvements seen in pharmacologic agents cannot be understated, especially when it comes to the management of high cholesterol, hypertension, and diabetes. These newer drugs have made terrific strides towards the risk reduction of stroke in patients with both symptomatic and asymptomatic carotid disease.  Next, there have been clinical trials that have compared carotid endarterectomy (CEA) to carotid artery stenting (CAS) amongst patients with symptomatic and asymptomatic disease.4-6

In addition to assessing the degree of stenosis, a good history and physical is crucial when deciding how to manage the patient with carotid disease. A good history and physical can help guide a clinician’s decision making on surgical management, or conservative treatment with other options. Ischemic strokes account for more than 80% of all strokes and roughly 20% of those are due to stenotic carotid arteries.1 While recent advances in pharmacologic management has helped to reduce the number of patients developing carotid stenosis, in the U.S. population, obesity remains on the rise and, unfortunately, despite public health warnings, many Americans continue to smoke.7 Both of which remain significant contributors to systemic vascular disease, not the least of which is carotid artery stenosis.1

The approach to carotid disease is largely based on symptoms and degree of stenosis. There are generally three possible scenarios to evaluate. Patients that are asymptomatic, yet, have an 80% or greater stenosis should be revascularized as soon as possible to prevent stroke.7 In patients that have completed a stroke, the approach is a little different, in that revascularization should be done within a two-week period following the initial event.1 During the two-week window, optimal medical therapy should be initiated.1,7 Thirdly, the patient that is actively having a TIA needs to be taken to the operating room urgently to revascularize the stenosis, with the goal of preventing an all-out stroke.1 The approach to these three potentially different clinical presentations are based on recommendations from the landmark CEA trials published in the mid 1990’s (NASCET, ECST, ACAS, ACST).1,7

Diagnostic Tools

Carotid artery stenosis can be diagnosed using several options. As it is non-invasive and lacks radiation exposure, duplex ultrasound (U/S) is currently the screening test of choice. Other options include CT angiography (CTA) and magnetic resonance angiography (MRA).3 CT exposes the patient to high-dose radiation and CT and MRA are very time consuming and costly. Also, to note, CTA will often times underestimate the degree of stenosis, while MRA will overestimate the degree of artery occlusion. CTA and MRA are usually only used in highly selective patients with lesions high in the neck, referred to as “high lesions”, where advanced imaging techniques would yield information the surgeon felt would be particularly helpful intraoperatively. Since most carotid lesions arise at the bifurcation of the internal and external carotid, the use of CTA and MRA are used less frequently by experienced vascular surgeons that perform frequent endarterectomies.

Symptomatic Carotid Stenosis

In patients with symptomatic carotid artery stenosis, the risk of stroke, recurrent stroke, or TIA can be minimized with revascularization of the internal carotid artery.1,8 The big question at this point becomes whether your patient is a better candidate for surgical intervention via CEA or the less invasive, CAS. With either of these choices, the clinician should always implement intensive pharmacologic therapy.1,9 To date, CEA remains the superior choice for carotid revascularization among asymptomatic and symptomatic patients that meet certain ultrasound criteria.7,10 Below is a list of ultrasound flow velocities that are used in vascular surgery to determine the degree of stenosis that is present in patients.11 These criteria are used to help guide decision making for revascularization.  If the patient is asymptomatic but has a lesion that is stenotic 80% or greater, revascularization is indicated and should be considered.8 If the patient has a stenotic lesion of greater than 70%, and is asymptomatic, revascularization is then considered.8

Velocity grading criteria based on the NASCET angiographic method11

Data that was published from the carotid revascularization endarterectomy versus stenting trial (CREST) indicated that CEA was superior to CAS.4 However, in a recently published 10-year follow-up to the CREST trial, new data have been published.5 The new data from the follow-up reveals that CEA was superior to CAS in the periprocedural period, resulting in fewer strokes.5 Nonetheless, once patients made it past the periprocedural timeframe, CEA and CAS were shown to be equal in terms of long-term treatments that can be employed for preventing an ischemic stroke in patients with symptomatic carotid stenosis.5

In terms of timing, the best possible time to revascularize a patient that is symptomatic is within two weeks of the inciting event.1 If it is decided between the patient and care team to wait past this two-week window, the overall benefits of revascularization have a sharp falloff.1 During the time period immediately following the CVA or TIA, at which revascularization can occur, patients should be started on intensive medical therapy.1,2 The recommended regimen for intensive medical therapy for these patients includes a high-intensity statin with a target LDL of < 70mg/dl, dual antiplatelet therapy agents, blood pressure (BP) regulation to maintain a systolic BP of < 140mmHg or < 130mmHg if diabetic, and a hemoglobin A1C < 7%.1,2,6 Other helpful therapies include lifestyle modifications that consists of smoking cessation, moderate exercise, and a goal to reduce their weight to ideal body weight.1

Carotid Artery Stenting

While CEA is currently the gold standard for revascularization of carotid stenosis, CAS is a second plausible option for patients.2,3 CAS materials and the technology to safely deploy them have improved significantly in the last decade.3 In addition to being an alternative to CEA for patients that are at risk for having surgery, CAS remains an option for those with advanced age, aberrant anatomy, or patients that have had radiation exposure to their neck.1,7 One potential concern with CAS is the periprocedural risk of stoke that exists. Therefore, the risk-benefit options should be discussed at length with the patient who is considering CAS.

As stent technology has been rapidly evolving, few stents have yet to deliver results superior to CEA. Though, in 2018 a study was published in Austria with very encouraging results.3 The study looked at a new stent design called the Casper Stent System, that was used in 138 patients.3 This double layered stent which demonstrated supreme vessel conformity, was deployed successfully without any technological failures or adverse neurological events within a ninety-day period, post stent placement.3 The main purpose of this new stent design is to lower or avoid altogether, the periprocedural stroke risks which were seen in the CREST trial as well as the ten-year follow-up from the CREST trial.3,4,12 The investigators from the Casper Stent System study suggest that the reduction in stroke and embolic events seen with their stent, are possibly as a result of its one of a kind dual layer design.3

Conclusion

The patient that was included in the introductory case presentation of this paper, despite being asymptomatic, did have a greater than 80% occlusion of the left internal carotid artery (ICA). He was taken to the operating room the day following his office visit and a CEA was successfully performed. Left, is a picture of the atheroma that was removed. Postoperatively he was admitted to the ICU where he developed some hypertensive issues requiring a continuous IV Nicardipine drip to help maintain an acceptable blood pressure. He didn’t experience any postoperative bleeding, neurological symptoms, or swelling.

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Most patients that are seen on the vascular surgery service can be adequately assessed for the need of carotid revascularization based on the degree of stenosis and whether or not they are experiencing symptoms or remain asymptomatic. Currently the method of choice for carotid revascularization remains CEA.1 However, in select high-risk patients with special anatomic considerations such as a “hostile neck” secondary to trauma, past surgery, or radiation, it is reasonable to consider pharmacologic or CAS therapy.1,9 Fortunately, CEA comes with a very low (<1%) risk of intraoperative or postoperative stroke if done by an experienced vascular surgeon, and offers the patient a significant risk reduction of experiencing stroke or TIA in the future.

Lastly, while the use of balloon angioplasty and stenting for coronary artery disease has been very successful, the use of stents in carotid disease has yet to prove superior to CEA in randomized controlled studies.6,8,9 CAS has emerging promise for those suffering from carotid disease in the not too distant future.3 As stent design evolves and pharmacologic protection of against embolus formation improves, CAS may be the way of the future for many vascular surgery services.2,3 The results of the CREST-2 Trial that are expected in 2020, will be interesting to see and will likely help reshape how we approach various aspects of carotid disease treatment.7 Stay tuned!

References:

1. Vavra AK, Eskandari MK. Treatment options for symptomatic carotid stenosis: timing and approach. Surgeon. 2015;13(1):44-51.

2. Noiphithak R, Liengudom A. Recent Update on Carotid Endarterectomy versus Carotid Artery Stenting. Cerebrovasc Dis. 2017;43(1-2):68-75.

3. Mutzenbach SJ, Millesi K, Roesler C, et al. The Casper Stent System for carotid artery stenosis. J Neurointerv Surg. 2018;10(9):869-873.

4. Brott TG, Hobson RW, 2nd, Howard G, et al. Stenting versus endarterectomy for treatment of carotid-artery stenosis. N Engl J Med. 2010;363(1):11-23.

5. Brott TG, Howard G, Roubin GS, et al. Long-Term Results of Stenting versus Endarterectomy for Carotid-Artery Stenosis. N Engl J Med. 2016;374(11):1021-1031.

6. Howard VJ, Meschia JF, Lal BK, et al. Carotid revascularization and medical management for asymptomatic carotid stenosis: Protocol of the CREST-2 clinical trials. Int J Stroke. 2017;12(7):770-778.

7. Safian RD. Asymptomatic Carotid Artery Stenosis: Revascularization. Prog Cardiovasc Dis. 2017;59(6):591-600.

8. Yu C, Han X, Zhang XL, Yu B, Dong Q. Long-term effects of white matter changes on the risk of stroke recurrence after carotid artery stenting in patients with symptomatic carotid artery stenosis. J Neurol Sci. 2016;369:11-14.

9. Cremonesi A, Castriota F, Secco GG, Macdonald S, Roffi M. Carotid artery stenting: an update. Eur Heart J. 2015;36(1):13-21.

10. Kakkos SK, Kakisis I, Tsolakis IA, Geroulakos G. Endarterectomy achieves lower stroke and death rates compared with stenting in patients with asymptomatic carotid stenosis. J Vasc Surg. 2017;66(2):607-617.

11. Simpson RJ, Akwei S, Hosseini AA, MacSweeney ST, Auer DP, Altaf N. MR imaging-detected carotid plaque hemorrhage is stable for 2 years and a marker for stenosis progression. AJNR Am J Neuroradiol. 2015;36(6):1171-1175.

12. Gurm HS, Yadav JS, Fayad P, et al. Long-term results of carotid stenting versus endarterectomy in high-risk patients. N Engl J Med. 2008;358(15):1572-1579.