Mock Circulation Simulation of Extracorporeal Membrane Oxygenation Support for Systemic Ventricular Failure in an Infant: The Effect of Atrial Septostomy

Extracorporeal membrane oxygenation (ECMO) is often used to provide cardiopulmonary support for infants experiencing severe levels of cardiac or respiratory failure. In patients with two ventricles and no intra-atrial communication, ECMO is often complicated by limited venous return to the circuit and marked left atrial hypertension. This condition may be treated by performing an atrial septostomy to create an intentional atrial septal defect (ASD). A pediatric mock circulation with a conduit connecting the left and right atrium was used to examine the size of ASD that would relieve left atrial hypertension and restore acceptable hemodynamics in a 4 to 5 kg infant. After creation of left ventricular failure and subsequent institution of ECMO, the ASD was opened in a graded fashion while the resulting hemodynamic changes were recorded. An ASD equivalent to a 6.3 mm diameter hole decreased the left atrial pressure 30 mmHg to an acceptable level with a net left-to-right shunt of 393 ml/min. Further opening of the ASD resulted in additional hemodynamic improvement, but was eventually limited in further effect. This study demonstrates that a mock circulation can be used to investigate the size of an ASD necessary to effect sufficient clinical improvement in a two-ventricle infant on ECMO.