Endovascular Revascularization of Symptomatic Chronically Occluded Internal Carotid Artery

Background:

Complete occlusion of the internal carotid artery (COICA) by atherosclerotic disease causes approximately 15%-25% of ischemic strokes in the carotid artery distribution. Patients treated with medical therapy have 5%-8% risk per year for ipsilateral ischemic stroke during the first 2 years after internal carotid artery occlusion. Internal carotid artery occlusion causes an estimated 61,000 first-ever strokes per year in the USA, an incidence more than twice the annual occurrence of ruptured intracranial aneurysms. Additionally, 40% of subjects with COICA who present with transient ischemic attacks (TIA) and 70% of COICA who present with stroke have cognitive decline with significantly increased risk of vascular dementia and Alzheimer's' disease (AD) with time 2,3.

Our group and others have used an alternative approach to revascularize subjects with COICAs. These studies showed the feasibility and safety of using endovascular angioplasty and stenting (EAS) and/or hybrid of both carotid endarterectomy (CEA) and EAS to restore cerebral flow to the ipsilateral hemisphere of the COICA. A meta-analysis of these studies, identified 333 subjects with COICA, an average age of 67.2 ± 9.3 years, and a male proportion of 85%. The average known occlusion time was 8.8 ± 10.0 months. Successful revascularization was achieved in 70% (232/333), with major complications found in 13 (3.9%) subjects and minor complications in 8 (2.4%) subjects. Furthermore, our group devised a new angiographic and anatomic classification to upfront predict the success of revascularization using these techniques. This classification was tested in 2 pilot studies and the results showed robust plausibility to predict upfront the percentage of success anticipated in revascularizing these lesions using these techniques. In addition, 3 groups including ours showed that revascularization using these techniques restored cerebral blood flow to the ipsilateral hemisphere of the COICA evident of normalization of mean transient time (MTT) on CT perfusion (CTP) and significant improvement in the cognitive function. Previous attempts to improve cognitive function in this cohort failed using bypass (COSS Trial).The rationale for failure is the fact that this technique relied on a very small caliber donor artery (STA) to revascularize the entire hemisphere affected. This significantly improved the oxygen extraction in the middle cerebral artery territory affected but failed to normalize it. Additionally, this technique provided cerebral flow to majority of ipsilateral middle cerberal artery territory but not enough to vascularize the Anterior cerebral artery territory, which supplies the majority of the limbic system involved in executive and cognitive functioning. EAS and hybrid technique restore the caliber of the cervical internal carotid arteryand therefore, the blood flow to all involved vessels (anterior and middle cerebral artery, and other branches) with clear evidence of complete resolution of penumbra and normalization of MTT on CTP. This could provide an explanation of the difference of both techniques in improving cognitive function.

All subjects who presents to our tertiary hospital with a diagnosis of COICA will undergo full evaluation including 1) documenting previous history of TIA and/or stroke; 2) cervical and brain CTA to document complete occlusion; 3) CTP to assess for presence of penumbra evident by increased MTT in the ipsilateral side of COICA; and 4) MoCA. If any subject is found to have complete occlusion of COICA, evident of abnormal/prolongation of MTT on CTP, previous history of TIA and or stroke, and MoCA <26 \& ≥ 23, then further evaluation is obtained including: 1H-MRI spectroscopy to assess for presence/absence of lactate in the ipsilateral watershed area (centrum semiovale), ratio of Naa/Cr, and size of ipsilateral hippocampus and amygdala, additional cognitive testing battery, and DSA to document adequately the type of COICA the subject have (type A-D).

If any subject does not have complete occlusion, or complete occlusion but no abnormalities on CTP and/or MoCA >26, then the subject is excluded and no further testing needed (see exclusion criteria).

If the subject meets all inclusion criteria, then a baseline of complete neurological testing, full demographics, CTA or MRA, CTP, MoCA, additional neurological testing (see below), 1H-MRI sectroscopy and DSA are obtained and subject is randomized 1:1 to either best medical management or best medical management + endovascular balloon angioplasty and stenting. Follow up clinic visits are arranged at 3 and 12 months. Repeat testing of MoCA and additional cognitive testing battery are done at these clinical follow-up visits (3 and 12 months). MRI of the brain and DSA is performed at 1 year follow-up to assess brain biomarkers and revascularization respectively.