BeGrow Study to Treat Pulmonary Artery (PA) Stenosis in Newborns and Infants

Inclusion Criteria: * Single lesion(s) which can be treated with a 6 mm BeGrow stent (only one stent per lesion allowed). * Pulmonary artery stenosis - patient must at least have one of the following diseases: * Haemodynamically relevant proximal or distal branch pulmonary artery stenosis with a reduction of the vessel diameter when the vessel/patient is large enough to accommodate a stent, * Haemodynamically relevant stenosis of the main pulmonary artery segment that results in elevation of the Right Ventricle (RV) pressure, provided that the stent definitely will not compromise a functioning pulmonary valve and will not impinge on the pulmonary artery bifurcation, * Any degree of stenosis in patients with single ventricle circulation * Critically ill postoperative cardiac patients when it has been determined that branch pulmonary artery stenosis is resulting in a definite haemodynamic compromise in a patient/vessel of any size, particularly if balloon dilatation is unsuccessful * Signed written informed consent (by parents/legal guardians) * Lesion can be accessed with a guide wire or balloon catheter * Age ≤ 24 months and weight ≥ 2 kg * Adequate stent length available Exclusion Criteria: * The following lesions are excluded from treatment with BeGrow stent: * Shunt stenosis * Valvular and subvalvular pulmonary stenosis * Patients with known hypersensitivity to the stent material (L605 cobalt-chromium). * Patients with clinical or biological signs of infection. * Patients with active endocarditis. * Patients with known allergy to acetylsalicylic acid, other antiplatelet agents or heparin. * Presence of other previously implanted stents in the same lesion or in close proximity to stent (direct stent-stent contact). * Patients with known coagulation disorder. * Patients where direct stent-stent contact or overlapping cannot be avoided. * Patients where contact to the vessel wall over the entire stent length cannot be ensured after dilatation (especially in short and thick lesions). * Patients where the BeGrow stent could protrude freely into adjacent vessels after expansion/dilatation, including the pulmonary arterial bifurcation. * Implantation of the BeGrow stent in the pulmonary arterial bifurcation.