Transcatheter creation and enlargement of interatrial defects (IAD) may improve hemodynamics; however, procedural outcomes have not been well defined. Hospital records were reviewed for children who underwent percutaneous procedures to create and enlarge an IAD and were grouped as follows: (1) right and (2) left heart obstructive lesions, (3) left atrial (LA) decompression during left heart assist, (4) failing Fontan circulation, and (5) miscellaneous. Forty-five children (mean age, 3.4 +/- 4.7 years; 30 (67%) male) were identified. In group 1 (n = 6), all achieved endpoints of right atrial (RA) decompression (n = 2), improved left ventricular filling (n = 3), or improved arterial saturations (n = 1). In group 2 (n = 18), mean LA pressure decreased (21 +/- 6 to 13 +/- 5 mmHg, p < 0.001) and arterial saturations increased (61 +/- 13% to 78 +/- 11%, p < 0.001). All except 2 patients achieved definitive repair, further palliation (n = 9), or heart transplantation (HTX) (n = 7). In group 3 (n = 5), the LA was decompressed (21 to 13 mmHg, p = 0.03) in all, and all except 1 patient survived to HTX (n = 2) or full recovery (n = 2). In group 4 (n = 11), of 7 patients with a low cardiac output syndrome after surgery, despite improved atrial shunting, 3 died and 1 required a HTX. In group 5 (n = 5), RA decompression (n = 1) or improved arterial saturation (n = 4) was achieved in all. Overall, 5-year HTX free survival was 75%. Mechanical ventilation before the procedure (p < 0.001), the need for a blade septostomy (p = 0.002), and higher LA pressures after the procedure (p = 0.04) independently predicted mortality or the requirement for HTX. Transcatheter optimization of an atrial communication can help optimize treatment strategies and has a low procedural risk.