P2.036: In-Utero Surveillance of Main Pulmonary Artery to Left Atrium Fistula with Urgent Postnatal Intervention

Introduction: Pulmonary artery (PA) to left atrium (LA) fistula is an incredibly rare congenital cardiac pathology, with less than 100 cases being reported. Often, this diagnosis is delayed until adulthood. Herein, we present an extremely rare case of a large main PA to LA fistula, initially diagnosed on fetal echocardiogram. Understanding the in-utero physiology offers critical information that can guide early postnatal intervention and thus improve neonatal cardiovascular outcomes. This case sheds light on the importance of prenatal imaging in early postnatal clinical decision making in a critically ill neonate that required urgent postnatal interventional cardiac catheterization.

Case Description: A 28-year-old mother was referred to fetal cardiology for a suspected fetal anomaly on routine obstetric ultrasound. Prenatal fetal echocardiograms initially demonstrated a main pulmonary artery (MPA) to LA fistula with significantly dilated MPA and hypoplastic branch PAs. Through serial fetal echocardiograms, there was consistent and worsening indicators of fetal distress, including severe cardiomegaly, umbilical arterial Doppler flow reversal, and initially indiscernible pulmonary venous return to the LA, a poor prognosticator. Fetal magnetic resonance imaging (MRI) performed at 38 weeks gestational age (GA) was notable for significantly diminished age-adjusted lung volumes. Three days after fetal MRI, a 2.9 kg female infant was born via induced vaginal delivery and required intubation, mechanical ventilation, initiation of inhaled nitric oxide (iNO), and vasopressors. Urgent post-natal echocardiogram confirmed prenatal cardiac findings. Given significant hypercarbia and severely diminished lung perfusion (Qp), in the setting of profound dead space ventilation, the patient underwent cardiac catheterization at hour-of-life two, with device closure of the fistula using a Type 1 Amplatzer duct occluder. Catheterization was performed with surgical and extracorporeal membrane oxygenation (ECMO) backup, which was ultimately not required, and the patient was transferred to the cardiac intensive care unit for further care.

Discussion: Literature demonstrates several cases of branch PA to LA fistulas – many of which were diagnosed postnatally, typically during late childhood or adulthood. MPA to LA fistulas are exceedingly rare, particularly with diagnosis in-utero. Caring for a patient with such rare cardiac anomaly such as this presents many challenges. Using data from serial fetal echocardiography and fetal MRI allowed us to prenatally employ a multidisciplinary approach including cardiology, cardiac intensive care, cardiothoracic surgery, and ECMO. Ultimately, prenatal surveillance helped guide prompt postnatal intervention, even in the context of abnormal lung physiology which is most significant life limiting factor.

Conclusion: MPA to LA fistula is a very rare congenital diagnosis, which may be missed until adulthood. Our use of serial fetal echocardiography, as well as advanced imaging with fetal MRI, allowed us to accurately diagnose this patient. Imaging also guided our management in planning for urgent interventional catheterization and device closure.