Sudden death, right sided heart failure (cor pulmonate or cardiovascular collapse occur when

CONSEQUENCES OF PULMONARY EMBOLISM i) Sudden death. Massive pulmonary embolism(60% or moreof pulmonary artery) results in instantaneous death, without occurrence of chest pain or dyspnoea. However, if the death is somewhat delayed, the clinical features resemble myocardial infarction i.e. severe chest pain, dyspnoea and shock. ii) Acute cor pulmonale. Numerous small emboli may obstruct most of the pulmonary circulation resulting in acute right heart failure. Another mechanism is by release of vasoconstrictor substances from platelets or by reflex vasoconstriction of pulmonary vessels. iii) Pulmonary infarction. Obstruction of relatively smallsized pulmonary arterial branches may result in pulmonary infarction . The clinical features include chest pain due to fibrinous pleuritis, haemoptysis and dyspnoea due to reduced functioning pulmonary parenchyma. iv) Pulmonary haemorrhage. Obstruction of terminal branches (endarteries) leads to central pulmonary haemorrhage. The clinical features are haemoptysis, dyspnoea, and less commonly, chest pain due to central location of pulmonary haemorrhage. Sometimes, there may be concomitant pulmonary infarction. v) Resolution. Vast majority of small pulmonary emboli (60-80%) are resolved by fibrinolytic activity. These patients are clinically silent owing to bronchial circulation so that lung parenchyma is adequately perfused. vi) Pulmonary hypertension, chronic cor pulmonale and pulmonary arteriosclerosis. These are the sequelae of multiple small thromboemboli undergoing healing rather than resolution.