The document discusses pulmonary embolism, which is the blockage of pulmonary arteries by blood clots or other materials. It defines pulmonary embolism and discusses its incidence, risk factors including deep vein thrombosis, clinical features such as chest pain and dyspnea, pathophysiology involving right heart strain, diagnostic studies, and treatment including anticoagulation with heparin and warfarin as well as surgical interventions in severe cases.