This is a real-world medical entrance exam question, please give the true answer based on the question and selection. Topic name: C.V.S, Subject name: Medicine
[{'content': 'RBBB with left Axis Detion Is characteristic of \nSelect and explain. \nA. Ostium Primum ASD, B. Mitral valve prolapse, C. Patent Ductus Aeriosus, D. Ventricular Septal Defect', 'role': 'user'}, {'content': 'Answer: A \nExplanation: Left axis detion may occur as a normal variant but is more commonly associated with left ventricular hyperophy, a block in the anterior fascicle of the left bundle system (left anterior fascicular block or hemiblock), or inferior myocardial infarction. In ostium primum ASD, the RV conduction defect is accompanied by left superior axis detion and counterclockwise rotation of the frontal plane QRS loop. ( Harrison&;s principle of internal medicine,18th edition,pg no.1834 )', 'role': 'assistant'}]