Prenatal interatrial septal aneurysm – an uncommon cause of hypoplastic appearance of the left heart

Purpose: We report a case of prenatal detected interatrial septal aneurysm which led to a significant ventricular dysbalance with dominant right heart and apparently hypoplastic left heart.

Case report: A 39 year old II gravida I para at 31+1 weeks of gestation was referred due to a suspected hypoplastic left heart. Indeed the cardiac ventricles showed significant dysbalance with dominant right heart and a small left heart and aorta ascendens. Therefore the 4-chamber-view seemed to be indicative for aortic stenosis. But no stenosis could be objectified. As reason of the striking ventricular appearance a large redundant structure at the level of the foramen ovale with abnormal bulging into the left atrium could be demonstrated. The distention of this flap compromised the mitral valve and led to a reduced left ventricular filling. The further course of the pregnancy was uneventful. A male neonate weighing 4190 g was delivered spontaneously at 39+3 weeks of gestation. APGAR scores were 9/9/9. A neonatal echocardiogram confirmed the prenatal findings. Follow up scans at day 2 and 17 showed a reduction and reversal of the interatrial shunt and a tightening of the septal aneurysm. The ventricular dysbalance ameliorated without hemodynamic disturbance.

Conclusion: Prenatal interatrial septal aneurysm can cause a misleading 4-chamber-view with apparently hypoplastic left heart. We demonstrate a case with decreased filling of the prenatal left heart but favorable postnatal outcome.