Abstract 14780: Analytical Identification of Stable Hemodynamic Conditions in Patients With Transposition of the Great Arteries
Introduction: Newborns with transposition of the great arteries (TGA) have systemic and pulmonary circulation in parallel; thus, mixing of both circulations is essential to maintain appropriate oxygen saturation level. However, shunt flow through a patent ductus arteriosus (PDA), ventricular septal defect (VSD), and atrial septal defect (ASD) may result in hemodynamic instability against a decrease in pulmonary arterial resistance. This tradeoff between oxygen saturation and hemodynamic stability should be fully understood for better management of patients with this unique circulation, but has never been elucidated.
Methods: We developed a lumped parameter model for TGA circulation based on the 3-element Windkessel model coupled with the time-varying elastance model of the ventricles. We examined the impacts of the shunt sizes and locations on oxygen saturation and cardiac index (CI) by combining various sizes of ASD, VSD and PDA. Contribution of each shunt to the mixing between systemic and pulmonary circulation was calculated based on the difference in oxygen saturation in each chamber.
Results: Seven combinations of the shunt sizes achieving oxygen saturation over 70% were identified and shunt through ASD had the greatest contribution to the mixing as shown in the Figure. Moreover, 50% reduction in pulmonary vascular resistance resulted in a 7% increase in oxygen saturation level and 4% increase in CI in those dependent on an ASD shunt (model A and C), and a 13% increase in oxygen saturation level and 7% decrease in CI in those dependent on a PDA shunt (model B and D). All the models dependent on a VSD shunt showed reduction in CI in response to reduction in pulmonary vascular resistance.
Conclusions: In clinician’s choice between prostaglandin infusion and atrial septostomy, the model predicted that utilizing an ASD shunt to maintain oxygen saturation level would be beneficial as it is more hemodynamically stable and more efficiently raises oxygen saturation.
Author Disclosures: R. Inuzuka: None. H. Senzaki: None.
- © 2016 by American Heart Association, Inc.