Rationale Fenfluramine (FFA) has been shown in 2 randomised, placebo-controlled clinical trials to reduce convulsive seizures in children with Dravet Syndrome (DS). We report an update on the cardiovascular safety of DS patients treated with FFA for up to 3 years.

Methods 327 patients who completed one of the three phase 3 trials enrolled in this open-label extension (OLE) study (NCT02823145). All were assessed with transthoracic echocardiography (TTE). They were assessed for Valvular Heart Disease (VHD) and Systolic pulmonary artery pressure.

Results One patient had a finding of mild MR (considered physiologic) during the study. One patient demonstrated mild (considered pathologic) AR at Month 15. A transoesophageal echocardiogram (TOE) performed at 6 weeks found absent AR with trace MR. No abnormalities of valve morphology were found on TOE or on TTE. No VHD or PAH was observed in any patient during the OLE.

Conclusions This study demonstrates the absence of clinically significant VHD or PAH supporting a positive benefit-risk profile for FFA in the treatment of patients with DS.