Abstract: 

Here we report two cases of extracorporeal membrane oxygenation (ECMO) support in pediatric patients following orthotopic heart transplantation due to low cardiac output and inability to separate from cardiopulmonary bypass (CPB). Both patients had significant donor/recipient size mismatch: ratios were 0.71 and 1.73. Cannulation was via the right atrium to ascending aorta using Maquet ECMO kits to achieve veno-arterial ECMO (VA-ECMO) configuration. Activated clotting time (ACT) was maintained at 150–170 seconds. Systemic blood pressure goals were a mean arterial pressure of 60–80 mmHg. Both patients successfully recovered the cardiac function and were discharged home without severe complications. ECMO can effectively support pediatric patients after orthotopic heart transplantation to successful recovery despite the use of extreme donor/recipient size mismatch.