Malposition of septum primum in isolated dextrocardia: unique and rare form of anomalous pulmonary venous return in association with partial absence of pericardium-case report

BACKGROUND: Total anomalous pulmonary venous return (TAPVR) refers to an anomaly in which all of the pulmonary veins drain directly or indirectly to the systemic venous circulation. However, unusual types constitute approximately 5% or less of TAPVRs and there may be obstruction or discontinuity of pulmonary vein at various levels. CASE PRESENTATION: A 3-month-old infant was presented to us with history of poor feeding, respiratory distress and desaturations. The routine echocardiographic investigation initially confirmed the diagnosis of an atrial septal defect with dextrocardia. However, due to disproportionate severity of symptoms and congestive heart failure a cardiac computer tomography angiogram was done that revealed a rare finding of connection of pulmonary veins fused with the posterior atrium, but on the rightward side of the deviated atrial septum. Therefore, pulmonary veins entered a sinus that drains directly into the right atrial superior-posterior wall. During surgical repair, we found an area of absent pericardium in the diaphragmatic surface of the heart. The patient underwent total repair of the TAPVR and patch reconstruction of the pericardial defect. The patient is doing well at 6-month follow up. CONCLUSIONS: The septum primum malposition defect resulting in TAPVR is a very rare congenital anomaly that can be rarely seen without any heterotaxy. The anomalous features including absent pericardium and dextrocardia were present in this patient have not been described previously with TAPVR. Therefore, we have hypothesized the embryological correlation of absent pericardium and cardiac malposition in such case. Transthoracic echocardiography with Doppler interrogation is a reliable method for diagnosing this condition. In case of suboptimal echocardiographic image due to cardiac position, unclear anatomy or unexplained symptoms, advanced imaging such as computer tomographic angiography or cardiac magnetic resonance imaging can be very helpful. Preoperative proper diagnosis of this anomaly facilitates successful surgical management with excellent outcome.