1. From the Cardiovascular Institute and Department of Pediatrics (M.R.) and Department of Medicine (M.R.N.), Stanford University School of Medicine, CA; INSERM UMR_S 999, LabEx LERMIT, Centre Chirurgical Marie Lannelongue, Le Plessis-Robinson and Université Paris-Sud, School of Medicine, Le Kremlin-Bicêtre (C.G., M.H.); and AP-HP, Service de Pneumologie, Centre de Référence de l’Hypertension Pulmonaire Sévère, DHU Thorax Innovation, Hôpital de Bicêtre, France (M.H.).