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: Pediatrics
[{'content': 'True about ASD – \nSelect and explain. \nA. Foramen ovale is patent, B. Left parasternal peeve is due to increased pulmonary artery flow, C. S2 is wide and variable, D. Systolic murmur is due to rapid flow of blood across the shunt.', 'role': 'user'}, {'content': 'Answer: B \nExplanation: Hemodynamics ofASD\xa0\xa0\xa0\xa0\xa0\xa0\xa0\xa0\xa0\xa0\xa0\xa0\xa0\xa0\xa0\xa0\xa0\xa0\xa0\xa0\xa0\xa0\xa0\xa0\xa0\xa0\xa0\xa0\xa0\xa0\nThere is abnormal connection between left and right atrium, which is due to defect in atrial septum (not a patent foramen ovale).\n\nBlood flows from left atrium to right atrium because left atrium has slightly higher pressure than right atrium → Left to right shunt.\nBecause the pressure difference between two atria is small, blood passes at a narrow pressure difference No shunt murmur.\nThere is volume overload to right atrium because of left to right shunt →.Right atrial dilatation and hypertrophy.\nDuring diastole large amount of blood passes from right atrium to right ventricle through tricuspid valve → delayed diastolic murmur and accentuation of first heart sound.\nVolume overload to right ventricle → Right ventricular hypertrophy that produces parasternal heeve.\nLarge blood volume passes through pulmonary valve → Pulmonary ejection murmur.\nProlonged blood passage along pulmonary valve causes delayed closure of pulmonary valve → P2 is delayed and accentuated, wide split and fixed S2.\nIncreased blood flow through pulmonary circulation → Pulmonary plethora that may cause pulmonary hypertension', 'role': 'assistant'}]