Peter A Schneider (San Francisco, USA) discusses the role stenting can play, alongside the existing best medical therapy, in treating asymptomatic carotid disease patients.
Best medical therapy (BMT) is mandatory in all patients with carotid occlusive disease. In addition, asymptomatic patients with a carotid stenosis greater than 80% and a reasonable long-term life expectancy should be considered for carotid bifurcation repair.
There is current conventional wisdom frequently being repeated suggesting that medical management of atherosclerotic occlusive disease has improved so much that repair of carotid bifurcation disease is no longer necessary. BMT has improved. However, it has not been evaluated as the sole treatment for patients with the severity of carotid occlusive disease that we would currently consider for repair.
Here are some features of the evolution of carotid disease management:
- Medical management has improved—but we do not know how much. Repeating frequently that BMT alone is adequate treatment for >80% asymptomatic stenosis does not make it so.
- No matter how effective medical management becomes, we will continue to face issues of compliance, side-effects and complications that prevent the reality of BMT in a substantial percentage of the patients.
- We can identify factors that put patients at increased risk for neurologic events from asymptomatic carotid bifurcation occlusive disease, including plaque progression, large plaque volume, intraplaque haemorrhage, silent cerebral infarcts, embolisation on transcranial Doppler, and other factors. These findings are associated with a 5–14% annual stroke risk.1–9
Almost all the data we have evaluating the efficacy of medical management of carotid bifurcation plaque comes from patients with mild-to-moderate lesions, which would not currently be considered for repair. This is true of several marquee studies that are routinely used to support a “medical management alone” advocacy (e.g. SMART, Oxford Vascular, ASED).
In the few studies that have evaluated the results of medical management of significant carotid plaques—those which we would currently consider for repair—the finding was in favour of repair plus best medical management.10, 11 One of the best examples is the Oxford Vascular Study.
This has been held for years as “evidence” that repair is not of value in addition to BMT. The study has a preponderance of patients with moderate carotid stenosis and the threshold for study entry was a peak systolic velocity of 150cm/seconds—a threshold that would be too low to ever be considered for repair in an asymptomatic patient. When the smaller cohort of patients with >80% carotid stenosis were evaluated, the rate of neurologic events on BMT was >20% at one year and nearly 30% at two years. 12
The results of carotid bifurcation repair have also improved, probably due to a combination of improved periprocedural medical management and new technology. The periprocedural stroke and death risk for carotid endarterectomy (CEA) in asymptomatic patients in CREST was 1.4% and in ACT I was 1.7%.13, 14 Some of this improvement may be due to improved periprocedural medical management with antiplatelet agents and statins. In addition, patients that qualify for repair, but who may have unfavourable anatomic characteristics for CEA, may be treated with transcarotid artery revascularisation (TCAR), which appears to be just as safe as CEA.
Carotid stenting can now be performed using TCAR, which includes direct sheath access to the common carotid artery with proximal clamping and carotid flow reversal. The combination of avoiding the aortic arch, initiating cerebral protection prior to crossing the lesion, and instituting flow reversal to prevent particulates from reaching the brain, have provided outstanding results for carotid stent placement using TCAR. The periprocedural stroke and death rate in the Roadster Trials were 1.3% in Roadster 1 and 0.9% in Roadster 2.15, 16 Among 9,435 patients analysed from the Vascular Quality Initiative (VQI) database, stroke or death occurred after CEA in 1.3% and after TCAR in 1.4% (p=0.49).17 Since TCAR is a relatively new procedure, there is the likelihood for continued improvement in results as various patient selection and technical aspects are refined.
TCAR has provided a less invasive alternative to CEA that appears to provide similar very low stroke and death rates, with a lower risk of myocardial infarction and a dramatically lower risk of cranial nerve injury. There are currently more than 20,000 TCAR cases in the VQI database sponsored by the Society for Vascular Surgery (SVS). As these are being analysed, we can see that excellent results can be achieved early in one’s experience, and that adding TCAR to a programme provides a net benefit with the availability of an additional option for repair. Currently, in the USA, asymptomatic carotid stenosis patients with >80% stenosis who have a minimum of a three-to-five-year life expectancy and a factor placing them at high risk for CEA can be eligible for TCAR.
The idea that low annual stroke risks with BMT can be inferred by evaluating patients with mild or moderate carotid occlusive disease—which we would not currently consider for carotid bifurcation repair—does not make any sense. In addition, repair of asymptomatic carotid disease in addition to BMT in well-selected patients can be performed with either CEA or TCAR with very low rates of stroke or death.
- Kakkos SK, Sabetai M, Tegos T, et al. Silent embolic infarcts on computed tomography brain scans and risk of ipsilateral hemispheric events in patients with asymptomatic internal carotid artery stenosis. J Vasc Surg 2009;49(4): 902–9.
- Spence JD, Tamayo A, Lownie SP, et al. Absence of microemboli on transcranial Doppler identifies low-risk patients with asymptomatic carotid stenosis. Stroke 2005;36(11): 2373–8.
- Topakian R, King A, Kwon SU, et al. Ultrasonic plaque echolucency and emboli signals predict stroke in asymptomatic carotid stenosis. Neurology 2011;77(8): 751–8.
- Conrad MF, Boulom V, Mukhopadhyay S, et al. Progression of asymptomatic carotid stenosis despite optimal medical therapy. J Vasc Surg 2013;58(1): 128–35.
- Shah Z, Masoomi R, Thapa R, et al. Optimal medical management reduces risk of disease progression and ischemic events in asymptomatic carotid stenosis patients: a long-term follow-up study. Cerebrovasc Dis 2017;44(3–4): 150–9.
- Kakkos SK, Griffin MB, Nicolaides AN, et al. The size of juxtaluminal hypoechoic area in ultrasound images of asymptomatic carotid plaques predicts the occurrence of stroke. J Vasc Surg 2013;57(3): 609–18.
- Naylor AR, Schroeder TV, Sillesen H, et al. Clinical and imaging features associated with an increased risk of late stroke in patients with asymptomatic carotid disease. Eur J Vasc Endovasc Surg 2014;48(6): 633–40.
- Hellings WE, Peeters W, Moll FL, et al. Composition of carotid atherosclerotic plaque is associated with cardiovascular outcome: a prognostic study. Circulation 2010;121(17): 1941–50.
- Garoff M, Ahlqvist J, Edin LT, et al. Bilateral vessel-outlining carotid artery calcifications in panoramic radiographs: an independent risk marker for vascular events. BMC Cardiovasc Disord 2019;19: 225.
- Conrad MF, Michalczyk MJ, Opalacz A, et al. The natural history of asymptomatic severe carotid artery stenosis. J Vasc Surg 2014;60(5): 1218–26.
- Kolos I, Troitskiy A, Balakhonova T, et al. Modern medical treatment with or without carotid endarterectomy for severe asymptomatic carotid atherosclerosis. J Vasc Surg 2015;62: 914–22.
- Howard DPJ, Gaziano L, Rothwell PM, et al. Risk of stroke in relation to degree of asymptomatic carotid stenosis: a population-based cohort study, systematic review, and meta-analysis. Lancet 2021;20(3): 193–202.
- Silver FL, Mackey A, Clark WM, et al. Safety of stenting and endarterectomy by symptomatic status in the Carotid Revascularization Endarterectomy Versus Stenting Trial (CREST). Stroke 2011;42(3): 675–80.
- Rosenfield K, Matsumura JS, Chaturvedi S, et al. Randomized Trial of Stent versus Surgery for Asymptomatic Carotid Stenosis. N Engl J Med 2016;374: 1011–20.
- Kwolek CJ, Jaff MR, Leal JI, et al. Results of the ROADSTER multicenter trial of transcarotid stenting with dynamic flow reversal. J Vasc Surg 2015;62: 1227–35.
- Kashyap VS, Schneider PA, Foteh M, et al. Early Outcomes in the ROADSTER 2 Study of Transcarotid Artery Revascularization in Patients With Significant Carotid Artery Disease. Stroke 2020;51(9): 2620–9.
- Malas MB, Dakour-Aridi H, Kashyap VS, et al. TransCarotid Revascularization with Dynamic Flow reversal versus Carotid Endarterectomy in the Vascular Quality Initiative Surveillance Project. Ann Vasc Surg.
Peter A Schneider is a professor of surgery in the Division of Vascular and Endovascular Surgery at the University of California San Francisco in San Francisco, USA.
The author discloses that they are a consultant for Silk Road Medical, Boston Scientific, and Medtronic.