Abstract Body: Background and Aims: Strategies for preventing radial artery spasms (RAS) during transracial cerebral angiography (TRA) have not been well-established. Papaverine has anti-vasospasm, sedative, and analgesic effects and is potentially effective for preventing RAS during TRA. The PASS trial aims to provide high-level evidence for this intervention.

Methods: PASS is a multicenter, randomized, placebo-controlled, double-blind trial (NCT05861765). Eligible participants scheduled for TRA are 1:1 randomly assigned to receive papaverine or placebo across four stroke centers in China. The experimental group will be slowly injected 10ml of papaverine hydrochloride solution (30mg/10ml) through the successfully implanted radial artery sheath and continuously dripped papaverine hydrochloride solution (60mg/500ml, 4ml/min) through the artery sheath during the procedure. The control group will be given normal saline in the same manner. The primary outcome is the incidence of RAS during the procedure, and PASS was designed with expectations of 4% vs 14.62% in the experimental and control groups, respectively, with a planned sample size of 240 subjects.

Results: The PASS trial received approval from the Ethics Committee of Sun Yat-sen Memorial Hospital and all participating centers. At the submission of this abstract, a total of 229 participants were successfully randomized. The study will be completed in November 2024 and final results will be presented at the ISC-2025.

Conclusions: The PASS trial is expected to provide robust evidence on the efficacy of papaverine to prevent RAS during TRA.