Anomalous drainage of inferior vena cava into left atrium associated with ostium secundum atrial septal defect: a case report

Background Anomalous drainage of inferior vena cava (IVC) into left atrium (LA) is a rare aetiology of cyanosis in adults. This condition may be associated with atrial septal defects, anomalous pulmonary venous drainage, and pulmonary arteriovenous fistulas. This case report presents an instance of anomalous drainage of IVC into LA, associated with ostium secundum atrial septal defect (ASD). It contributes to the existing literature by highlighting the diagnostic challenges associated with this anomaly, particularly during surgical intervention.Case summary A 38-year-old male presented with a six-year history of exertional dyspnoea and episodic palpitation. Transthoracic echocardiography revealed a large secundum (ASD), the IVC draining into LA, a left superior vena cava, and mild mitral regurgitation. These findings were further confirmed by right and left heart catheterization and CT angiogram. The patient was referred to CTVS department for surgical correction. The post-operative course was uneventful. At a 1.4-year follow-up, the patient reported significant improvement in symptoms.Discussion We present a case of anomalous drainage of IVC into LA, associated with ostium secundum ASD. An ASD co-occurs with this condition in similar to 70% of the reported cases. This anomaly differs from a low or inferior vena caval secundum ASD, where a prominent Eustachian valve can cause blood shunting from the IVC to LA. If the surgeon is not vigilant, this can be mistaken for the inferior ASD rim, potentially leading to iatrogenic diversion of IVC blood to LA upon ASD closure, resulting in cyanosis. This case underscores the diagnostic and surgical challenges associated with this condition.