The study is a multi-center, randomized, double-blind, placebo-controlled study to evaluate the efficacy and safety of etripamil NS self-administered by patients who experience an episode of PSVT in an at-home setting.~This is an event-driven study. Enrollment into the study will continue until the adjudication of the 180th positively adjudicated PSVT episode in patients treated with double-blind study drug during the Randomized Treatment Period required for the study's pivotal analysis. After the date of the adjudication of the 180th positively adjudicated PSVT episode, all randomized patients will be unblinded at this timepoint and enter into an approximately 6 months open-label period of the study.
To determine whether etripamil nasal spray (NS) self-administered by Chinese patients is superior to placebo at terminating episodes of PSVT in an at-home setting； To evaluate the efficacy of etripamil NS self-administered by Chinese patients compared with placebo on a range of clinical markers.~To evaluate the safety of etripamil NS self-administered by Chinese patients compared with placebo