Symptomatic Carotid Occlusion Is Frequently Associated With Microembolization

Abstract

Background and Purpose Symptomatic carotid artery disease is associated with significant morbidity and mortality. The pathophysiologic mechanisms of cerebral ischemia among patients with carotid occlusion remain underexplored. Methods We conducted a prospective observational cohort study of patients hospitalized within seven days of ischemic stroke (IS) or transient ischemic attack (TIA) due to ≥50% carotid artery stenosis or occlusion. Transcranial Doppler (TCD) emboli detection was performed in the middle cerebral artery ipsilateral to the symptomatic carotid. We describe the prevalence of microembolic signals (MES), characterize infarct topography, and report clinical outcomes at 90-days. Results Forty-seven patients, 19 with carotid occlusion and 28 with carotid stenosis, had complete TCD recordings and were included in the final analysis. MES were present in 38%. There was no difference in MES between those with carotid occlusion (7/19, 37%) compared to stenosis (11/28, 39%; p=0.87). In patients with radiographic evidence of infarction (n=39), 38% had a watershed pattern of infarction, 41% had a non-watershed pattern, and 21% had a combination. MES were present in 40% of patients with an exclusively watershed pattern of infarction. Recurrent cerebral ischemia occurred in 9 patients (19%; 6 with TIA, 3 with IS). There was no difference in the rate of recurrence in those with compared to without MES. Conclusion Cerebral embolization plays an important role in the pathophysiology of ischemia in both carotid occlusion and stenosis, even among patients with watershed infarcts. The role of aggressive antithrombotic and/or antiplatelet therapy for symptomatic carotid occlusions may warrant further investigation given our findings.

Mechanisms for Recurrent Strokes in the Territory of an Internal Carotid Artery Occlusion

“…Notably, microembolic signals were found in equal rates in watershed and non-watershed infarcts using transcranial Doppler, suggesting a role for embolization in ischemic infarcts where cerebral hypoperfusion is suspected as a primary mechanism. 7 Regarding the mechanism of strokes in this patient, multiple CTAs demonstrated a persistently occluded left ICA with a proximal "stump." Although the patient initially had multifocal infarcts suggestive of a thromboembolic process, cerebral hypoperfusion was a likely etiology for many of his infarcts and TIAs and was supported by impaired hemodynamics observed using CTP.…”

A narrative review of the pathophysiology of ischemic stroke in carotid plaques: a distinction versus a compromise between hemodynamic and embolic mechanism

“…An experimental study conducted in nonhuman primates showed that subsequent WS infarcts affected both cortical and deep WS zones (119). In a clinical study, ipsilateral MES were common in patients with recent WS infarct related to carotid artery stenosis or occlusion thus demonstrating an embolic mechanism from the plaque (120). In the same way, carotid intraplaque hemorrhage, a marker of plaque instability, tended to be associated with WS infarcts in the absence of severe hemodynamic impairment (121).…”

Long‐term outcomes of carotid artery stenting in patients with a contralateral carotid artery occlusion

“…Carotid artery stenosis is a well‐established risk factor for transient ischemic attacks (TIAs) and ischemic strokes . Carotid artery stenosis can lead to TIA and stroke from either low‐flow states due to the stenosis or from ulcerated plaque embolization . Treatment options include medical therapy alone, or medical therapy with revascularization (either carotid endarterectomy [CEA] or carotid artery stenting [CAS]).…”