Background Pulmonary arterial hypertension (PAH) may occur in up to 50% of patients with congenital heart disease resulting in left-to-right shunt. The development of arterial pulmonary vascular disease is determined by the type, size and natural history of the defect. There have been cases where small cardiac defects resulted in disproportionate degrees of PAH.

Methods We exhibit two cases of medium-sized secundum atrial septal defects (ASDs) that evolved with severe PAH, disproportionate considering the size of the defects, which were assessed by ECG, echocardiography and right heart catheterization and are now receiving specific drug therapy.

Results The demographic, clinical, ECG, echo and right heart catheterization data as well as treatment details are as follows: current age (8 years, 11 years), age at time of diagnosis (4 years, at birth), Sex (1 male), associated syndromes (1 pt Down Syndrome), chest wall deformities (2 pts), Oxygen saturation (98%, 81%), ECG changes : right atrial enlargement – 2 pts, right ventricular hypertrophy 2 pts, right axis deviation 2 pts, Echocardiography : dilated right cavities 1 pt, tricuspid regurgitation 2 pts, Right Heart (RH) Catheterization – Mean pulmonary arterial pressure: 63 mm Hg, 38 mmm Hg, Pulmonary vascular resistance: 7 U Wood, 11,3 U Wood, Pulmonary-Systemic flow ratio (Qp:Qs) 1,2: 1, 1: 1, Specific PAH drug : Bosentan + Sildenafil 2 pts.

Conclusion Both patients feature severe PAH diagnosed at an early stage of a medium-sized secundum ASD. The question is whether the noted pulmonary hypertension (PH) is due to a primary disorder of the pulmonary arteries or whether it is a case of fast evolving congenital heart disease associated PH.