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': 'All of the following statements regarding total anomalous pulmonary connection are true except – \nSelect and explain. \nA. The total pulmonary venous blood reaches the right atrium, B. Always associated with a VSD, C. The oxygen saturation of the blood in the pulmonary artery is higher than that in the aorta, D. Infracardiac type is always obstructive', 'role': 'user'}, {'content': "Answer: B \nExplanation: Hemodynamics of TAPVC \n\nTAPVC results in the pulmonary venous blood reaching the right atrium which also receives the systemic venous blood.\nThis results in volume overload to right atrium -p Right atrial enlargement.\nLarger volume of blood reaches the right ventricle --> Right ventricle enlargement.\nThe blood flow to the left atrium is through patent foramen ovale or ASD.\nBecause there is mixing of unoxygenated blood from systemic circulation and oxygenated blood from pulmonary circulation in the right atrium —> The oxygen saturation of blood in pulmonary artery is higher or identical to that in Aorta.\nTAPVC can be divided into : -\n\ni) TAPVC with pulmonary venous obstruction\n\nPulmonary venous obstruction results in pulmonary arterial hypertension. Pulmonary obstruction —> T back pressure —> 1' Pulmonary capillary pressure\n\nT Pulmonary artery pressure\nu Because of pulmonary venous obstruction oxygenated blood cannot reach heart —> Cyanosis and CHF during first week of life.\nii) TAPVC without obstruction (more common)\n\nIn TAPVC without obstruction, pulmonary blood flow is high.\nPatients develops CHF at around 6-8 weeks when the fetal pulmonary resistance falls maximally and pulmonary circulation reaches the maximum.\nInfracardiac type of TAPVC is always obstructive whereas cardiac and supracardiac type may be obstructive or nonobstructive.", 'role': 'assistant'}]