How to identify which patients with asymptomatic carotid stenosis could benefit from endarterectomy or stenting

Abstract

Offering routine carotid endarterectomy (CEA) or carotid artery stenting (CAS) to patients with asymptomatic carotid artery stenosis (ACS) is no longer considered as the optimal management of these patients. Equally suboptimal, however, is the policy of offering only best medical treatment (BMT) to all patients with ACS and not considering any of them for prophylactic CEA. In the last few years, there have been many studies aiming to identify reliable predictors of future cerebrovascular events that would allow the identification of patients with high-risk ACS and offer a prophylactic carotid intervention only to these patients to prevent them from becoming symptomatic. All patients with ACS should receive BMT. The present article will summarise the evidence suggesting ways to identify these high-risk asymptomatic individuals, namely: (1) microemboli detection on transcranial Doppler, (2) plaque echolucency on Duplex ultrasound, (3) progression in the severity of ACS, (4) silent embolic infarcts on brain CT/MRI, (5) reduced cerebrovascular reserve, (6) increased size of juxtaluminal hypoechoic area, (7) identification of intraplaque haemorrhage using MRI and (8) carotid ulceration. The evidence suggests that approximately 10%-15% of patents with asymptomatic stenosis might benefit from intervention; this will become more clear after publication of ongoing studies comparing stenting or endarterectomy with best medical therapy. In the meantime, no patient should be offered intervention unless there is evidence of high risk of ipsilateral stroke, from modalities such as those discussed here.

Figure 1

Transcranial Doppler embolus detection. Microembolus in a patient with asymptomatic carotid stenosis. The upper channel is an M-mode image of an embolus in the middle cerebral artery; the lower panel shows the high-intensity transit signal in the Doppler channel. Besides the visual appearance of the microembolus, a characteristic clicking sound is heard. (Reproduced by permission of the Society for Vascular Ultrasound from: Spence JD. Transcranial Doppler: uses in stroke prevention. The Journal for Vascular Ultrasound 2015;39:183–7.)

Figure 2

Carotid ulcer volume as a predictor of risk. (A) Measurement of ulcer volume and ulcer depth. Contours of ulcers were traced and depth of ulcers measured in cross-sectional views. Each slice had a thickness of 1 mm; total ulcer volume (TUV) was computed from the sum of the volumes of all slices in which ulceration was traced. (B) Kaplan–Meier survival analysis curves for participants with TUV≥5.00 mm³ and those with no ulcerations or TUV<5 mm³. Time is shown in days until the first occurrence of any of the following events: stroke, TIA or cardiovascular death during the duration of follow-up; log-rank P=0.009. TIA, transient ischaemic attack; TUV, total ulcer volume. (Reproduced by permission of Wolters Kluwer Health. from: Kuk M, Wannarong T, Beletsky V, Parraga G, Fenster A, Spence JD. Volume of Carotid Artery Ulceration as a predictor of Cardiovascular Events. Stroke 2014;45:1437–41.)

Figure 3

Event-free survival in asymptomatic carotid stenosis with and without microemboli on transcranial Doppler since 2003. After more intensive medical therapy based on ‘treating arteries’, two or more microemboli on TCD remained a significant predictor of stroke/TIA/death, but to a lesser degree than before 2003. TIA, transient ischaemic attack; TCD, transcranial Doppler. (Reproduced by permission of the Society for Vascular Ultrasound from: Spence JD. Transcranial Doppler: uses in stroke prevention. The Journal for Vascular Ultrasound 2015;39:183–7.)

Figure 4

Imaging of active calcification by PET/CT with ^[18]F Sodium Fluoride. NaF PET/CT imaging of left and right internal carotid arteries of active calcification in a 72-year-old symptomatic patient evaluated at the University of Ottawa Heart Institute. Upper row: evidence of NaF uptake with a small foci of calcification on CT in the left internal carotid symptomatic culprit vessel. There is a mismatch between the region of NaF uptake and calcification on CT. Lower row: evidence of calcium nodules with matched NaF uptake at the right internal carotid artery. PET, positron emission tomography. (Reproduced by permission of the Journal of Nuclear Cardiology from: Cocker MS, Mc Ardle B, Spence JD, et al. Imaging atherosclerosis with hybrid [(18)F]fluorodeoxyglucose positron emission tomography/CT imaging: What Leonardo da Vinci could not see. J Nucl Cardiol 2012;19:1211–25.)