paeds53
A 5 month old boy presents with breathlessness, central cyanosis, irregular pulse, and oedema. On cardiac auscultation, he has a displaced apical beat laterally and a profound right ventricular heave. On lung auscultation, he has bilateral basal crackles. X-ray of the chest reveals gross cardiomegaly. Heart ultrasound shows mitral valve prolapse. Finally, ECG shows a prolonged and widened QRS complex with a short PR interval. Doctors establish the diagnosis of a right bundle branch block with a dominant R wave in V1. What is the most likely diagnosis?