Prospective multicenter study of consecutive patients with acute ischemic stroke and large intracranial vessel occlusion in which a thorough and systematic evaluation of all variables that may be related to the degree of collateral circulation is performed.

Introduction. In patients with an acute ischemic stroke due to a large-vessel intracranial occlusion (LVO), the status of the colateral circulation (CC) is related to clinical outcome and to the success of mechanical thrombectomy. However, CC is highly variable from patient to patient.

Methods. An observational, prospective, multicenter study of 700 consecutive patients with acute ischemic stroke and a LVO. Factors to be evaluated: 1) Modifiable: Vascular risk factors, blood analysis, prior medications, vital constants (with emphasis on continuous blood pressure monitoring), head position, metrics (time to admission, Computed tomography (CT), groin puncture, end of procedure), 2) Non-modifiable: age, sex, completeness of Circle of Willis, etiology, type of mechanical thrombectomy, plasma biomarkers, genetic/epigenetic factors (a discovery phase with GWAs study and a replication phase). CC grade will be assessed by the ASITN/SIR collateral score from CT-angiography (CTA) and the Digital substraction angiography (DSA, when performed). Statistics: bivariate analyses and a logistic regression to predict CC grade (poor versus good) and CC persistence comparing CTA with DSA (4 possibilities: poor-poor, poor-good, good-poor, good-good).

Expected results. Our study may find markers of the CC status, facilitate the design of clinical trials to improve CC grade, may find new therapeutic targets and new treatments to enhance the beneficial effects of mechanical thrombectomy.

Inclusion Criteria:

• Patients with acute ischemic stroke.
• Large vessel occlusion of an intracranial internal artery: M1, M2 or TICA. (terminal intracranial carotid artery), as demonstrated by CTA.
• CTA performed within the first 24 hours after stroke onset. Patients with wake-up stroke are included.
• A previous modified Rankin Scale score of 0 to 3.
• The patient or a legal representative signs a written consent to participate.

Exclusion Criteria:

• More than 24 hours from last been known to be well.
• Occlusion of other arterial segments (vertebrobasilar circulation, A1, P1, M3, M4).
• Age below 18 years.

Patients with acute ischemic stroke and a large-vessel intracranial occlusion.