Pulmonary Atresia with Ventricular Septal Defect and Major Aortopulmonary Collateral Arteries Misdiagnosed as Tetralogy of Fallot: A Series of Three Cases

Background Tetralogy of Fallot (TOF) is the most prevalent cyanotic congenital heart disease. Pulmonary atresia with ventricular septal defect (PA-VSD) is a life-threatening cardiac malformation that shares phenotypic similarities with TOF but differs substantially in terms of treatment strategies and long-term prognosis. Echocardiography plays a pivotal role in distinguishing TOF with severe pulmonary stenosis from PA-VSD accompanied by major aortopulmonary collateral arteries (MAPCAs); however, this distinction remains clinically challenging due to overlapping imaging features. Case Presentation : We report three patients who were initially diagnosed with TOF via transthoracic echocardiography. All patients exhibited four key echocardiographic findings consistent with PA-VSD: pulmonary valve atresia, large malaligned ventricular septal defect (VSD), aortic overriding, and MAPCAs. Two patients were diagnosed with TOF shortly after birth, did not undergo surgical intervention, and remained clinically stable until the current presentation. The third patient was re-evaluated preoperatively with comprehensive imaging, which confirmed PA-VSD with MAPCAs, followed by successful surgical correction. Conclusion This case series underscores the diagnostic pitfalls of relying exclusively on echocardiography to differentiate severe TOF from PA-VSD with MAPCAs. The presence of MAPCAs should trigger a high index of suspicion for PA-VSD rather than severe TOF. For echocardiographic diagnosis of TOF, it is imperative to clearly demonstrate high-velocity flow signals indicative of pulmonary stenosis and to meticulously assess for the presence of MAPCAs or patent ductus arteriosus (PDA). Accurate echocardiographic characterization is critical for formulating optimal, patient-specific treatment plans and avoiding adverse surgical outcomes.