Summary of study protocol and main study findings. Unaffected carriers (UCs) of pathogenic BMPR2 variants and healthy family members (controls) were recruited for study participation after genetic counselling. A multimodality screening approach was employed with UCs undergoing an additional right heart catheterisation (RHC) at baseline and at the 4-year follow-up (T4). Main study findings include lower indexed right ventricular (RV) end-systolic volume (ESVi) and RV end-diastolic volume (EDVi) in UCs as well as a higher RV global circumferential strain (GCS) (red dots indicate phenoconverters). Haemodynamic and pressure–volume loop analysis showed higher RV end-systolic elastance (Ees), RV afterload (arterial elastance (Ea)) and altered RV pulmonary artery (PA) coupling (Ees/Ea) in UCs. During the study, two participants developed pulmonary arterial hypertension (PAH). MRI: magnetic resonance imaging; NT-proBNP: N-terminal pro-brain natriuretic peptide; NYHA: New York Heart Association; TTE: transthoracic echocardiography; V′_E: minute ventilation; V′_CO2: carbon dioxide production.