Van Praagh Type A3 Truncus Arteriosus in a 47-Year-Old man: Correcting a Misdiagnosis via Multimodal Imaging——A Case Report

Background Persistent truncus arteriosus (TA) is a rare conotruncal anomaly characterized by a single arterial trunk supplying the systemic, pulmonary, and coronary circulations. Unrepaired survival into the fifth decade is exceptional. This case highlights the complementary roles of transthoracic echocardiography (TTE) and computed tomography angiography (CTA) in resolving longstanding diagnostic uncertainty and delineating complex pulmonary arterial and collateral anatomy. Case summary A 47-year-old man diagnosed with tetralogy of Fallot after birth, but who received no corrective treatment or subsequent cardiac follow-up, presented with recurrent haemoptysis. He had marked cyanosis, severe hypoxaemia (SpO2 84%), and secondary erythrocytosis, but no overt decompensated heart failure. TTE demonstrated a common trunk overriding of a large ventricular septal defect with bidirectional shunting, moderate truncal valve regurgitation, and preserved biventricular systolic function, but failed to clearly define the origin of the left pulmonary artery. CTA established Van Praagh type A3 TA, with the left pulmonary artery arising from the distal common trunk, absence of the native right pulmonary artery, and collateral-dependent right lung perfusion. Cardiac catheterisation was declined. Haemoptysis subsided with conservative treatment, but severe hypoxaemia persisted (SpO2 84%), and the patient requested early discharge against medical advice. Conclusion Multimodal imaging corrected a longstanding diagnostic misclassification, clarified the asymmetric pulmonary arterial and collateral anatomy, and suggested possible mechanisms for prolonged survival and haemoptysis. Although reclassification did not alter the immediate conservative management, it refined the differential diagnosis and provided an anatomical basis for future surveillance.