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: Pathology
[{'content': 'Sudden death, right sided heart failure (cor pulmonate or cardiovascular collapse occur when \nSelect and explain. \nA. Small pulmonary embolism, B. Massive pulmonary embolism, C. 60% or more of pulmonary artery is obstructed with emboli, D. End artery obliteration', 'role': 'user'}, {'content': 'Answer: C \nExplanation: CONSEQUENCES OF PULMONARY EMBOLISM\ni) Sudden death. Massive pulmonary embolism(60% or moreof pulmonary artery) results in\xa0instantaneous death, without occurrence of chest pain or\ndyspnoea. However, if the death is somewhat delayed, the\xa0clinical features resemble myocardial infarction i.e. severe\nchest pain, dyspnoea and shock.\nii) Acute cor pulmonale. Numerous small emboli may\xa0obstruct most of the pulmonary circulation resulting in acute\nright heart failure. Another mechanism is by release of\xa0vasoconstrictor substances from platelets or by reflex\nvasoconstriction of pulmonary vessels.\niii) Pulmonary infarction. Obstruction of relatively smallsized\xa0pulmonary arterial branches may result in pulmonary\ninfarction . The clinical features include chest pain\xa0due to fibrinous pleuritis, haemoptysis and dyspnoea due\nto reduced functioning pulmonary parenchyma.\niv) Pulmonary haemorrhage. Obstruction of terminal\xa0branches (endarteries) leads to central pulmonary\nhaemorrhage. The clinical features are haemoptysis,\xa0dyspnoea, and less commonly, chest pain due to central\nlocation of pulmonary haemorrhage. Sometimes, there may\xa0be concomitant pulmonary infarction.\nv) Resolution. Vast majority of small pulmonary emboli\xa0(60-80%) are resolved by fibrinolytic activity. These patients\nare clinically silent owing to bronchial circulation so that lung\xa0parenchyma is adequately perfused.\nvi) Pulmonary hypertension, chronic cor pulmonale and\xa0pulmonary arteriosclerosis. These are the sequelae of\nmultiple small thromboemboli undergoing healing rather\nthan resolution.', 'role': 'assistant'}]