Abstract 16168: Maternal Hyperoxygenation Improves Left Heart Filling in the Fetus With Atrial Septal Aneurysm Causing Impediment to Left Ventricular Inflow
Background: Aneurysm of the atrial septum (AAS) with excessive excursion of septum primum into the left atrium is an uncommon condition in the fetus which can cause impediment to filling of the left ventricle (LV) and the appearance of an under-filled, small LV on fetal echocardiography. Impediment to filling can be so severe as to create the image of LV hypoplasia with retrograde aortic flow. We sought to investigate whether maternal hyperoxygenation (MH), by increasing fetal pulmonary venous return, could alter atrial septal position, improve LV filling with alteration in geometry, and normalize direction of aortic flow in AAS.
Methods and Results: Twelve fetuses referred for evaluation of LV hypoplasia, were found to have AAS with marked bowing of redundant atrial septum right to left. Fetal echocardiography was performed prior to and after 10 minutes of MH with 60% O2 via non re-breather face mask. Measures included the degree of atrial septal excursion (ASE) as the maximum length of excursion of septum primum divided by the left atrial diameter; LV and RV sphericity index (SI) as the ratio of short axis-to-long axis ventricular cavity dimensions; and direction of flow in the aortic isthmus on Doppler evaluation. Following MH (35± 3 weeks gestation) ASE decreased (0.76± 0.17 to 0.53± 0.23, p<0.01) suggesting increased pulmonary venous return, LV SI increased (0.29± 0.06 to 0.42± 0.06, p<0.001) indicating increased LV filling, and direction of aortic isthmus flow changed from retrograde in all cases before MH to antegrade (n=10) or bidirectional (n=2) after MH. RV SI did not change with MH (0.53± 0.13 to 0.52± 0.10, p=0.7). At birth, LV cavity appeared normal in all with no concerns about adequacy; 2 had coarctation of the aorta, one of which had significant increase in aortic isthmus peak velocity with MH.
Conclusion: In AAS, short term MH leads to pulmonary vasodilation with increased pulmonary venous return and substantial improvement in LV geometry by increased filling, which influences direction of flow in the aortic isthmus. These findings raise the possibility that sustained MH may provide a means for increasing left heart flow in the fetus, which may improve cerebral perfusion or influence the growth of left heart structures in those with true anatomical LV hypoplasia.
- © 2013 by American Heart Association, Inc.