This is a real-world medical entrance exam question, please give the true answer based on the question and selection. Topic name: None, Subject name: Medicine
[{'content': 'A middle aged lady was diagnosed to incidentally have a ejection systolic murmur at the pulmonary area. A fixed wide split of the second heart sound was also noted. The diagnosis is:- \nSelect and explain. \nA. Tetralogy of Fallot, B. Atrial septal defect, C. Mitral stenosis, D. Mitral valve prolapse', 'role': 'user'}, {'content': 'Answer: B \nExplanation: Classically presents as an asymptomatic patient with a ﬂow murmur in the pulmonary area and a ﬁxed\xa0 wide split of S2.\nAtrial septal defects occur most commonly in the region of the fossa ovalis, referred to as secundum-type defects .Additional atrial\xa0 septal\xa0 defects\xa0 include\xa0 defects\xa0 of\xa0 the\xa0 sinus\xa0 venosus\xa0 and\xa0 atrium primum. Color flow Doppler echocardiography is usually sufficient for diagnosis of a secundum-type atrial septal defect, but agitated saline is\xa0generally\xa0needed\xa0for\xa0the\xa0diagnosis\xa0of\xa0other\xa0types\xa0of\xa0atrial\xa0septal defects.', 'role': 'assistant'}]