Atrial septal defect (ASD) occlusion in adult patients with advanced age and left or right heart diastolic or systolic heart failure and in patients with pulmonary arterial hypertension bears a considerable risk of deterioration of heart failure. Therefore, we conducted this feasibility trial in 15 ASD patients with pulmonary hypertension and/or right heart failure using a fenestrated Amplatzer septal occluder (AGA Medical Corporation, Golden Valley, MN), allowing an overflow of blood in both directions in case of univentricular diastolic or systolic heart failure. In all patients, the device could be implanted without complications. All symptomatic patients showed an improvement in the New York Heart Association (NYHA) class, and no right or left heart decompensation occurred. On echocardiography, right ventricular end diastolic dimension (RVEDD) and pulmonary artery pressure (PAP) decreased significantly, whereas left ventricular end diastolic dimension (LVEDD) increased. Our series of 15 patients with fenestrated ASD occlusion shows that high-risk ASD occlusion can safely be accomplished with excellent clinical results and without complications by a fenestrated occluder.