Head Down Tilt 15° to Increase Collateral Flow in Acute Ischemic Stroke: Rationale and Study Protocol of a Multicenter, Randomized, Proof-of-Concept, Phase 2a/b Trial in Patients Treated With Mechanical Thrombectomy (DOWN-SUITE)

BACKGROUND: Collateral blood flow is a critical determinant of successful recanalization in acute ischemic stroke caused by large vessel occlusion. Head down tilt −15° (HDT15), similar to Trendelenburg positioning, is a simple, low-cost positional therapy that may augment cerebral collateral blood flow and penumbral survival. The aim of the study is to assess the safety, feasibility, and efficacy of HDT15 in improving cerebral collateral circulation and clinical outcomes in patients with large vessel occlusion–acute ischemic stroke treated with mechanical thrombectomy (MT). METHODS: The DOWN-SUITE trial (Head Down Tilt 15° to Increase Collateral Flow in Acute Ischemic Stroke) is a multicenter, randomized, open-label, phase 2a/b clinical trial with blinded outcome assessment, conducted across 7 Italian stroke centers. A total of 118 patients with acute ischemic stroke due to M1 segment middle cerebral artery occlusion will be randomized 1:1 in the emergency department to receive HDT15 or standard positioning (head-of-bed 0° to +30°) before and during MT. RESULTS: The primary end point is good collateral status (American Society of Interventional and Therapeutic Neuroradiology/Society of Interventional Radiology grade 3–4), assessed on the first angiographic sequence during MT by a blinded imaging core laboratory. Secondary end points include feasibility (proportion maintaining HDT15, admission-to-MT time), safety (symptomatic intracranial hemorrhage, pneumonia, vomiting, neurological deterioration, vital signs), and efficacy (neurological improvement before MT, at 24 hours, and at 7 days or discharge, modified Rankin Scale score at 90 days). CONCLUSIONS: The DOWN-SUITE trial will provide evidence on the acute cerebrovascular effect of HDT15 in large vessel occlusion–acute ischemic stroke, potentially establishing a cost-effective, practice-changing intervention to improve collaterals for global stroke care. REGISTRATION: URL: https://www.clinicaltrials.gov ; Unique identifier: NCT06297863.