Acute pulmonary embolism is a deadly event that occurs in 1 per 1000 persons and is responsible for 50 000 to 100 000 deaths each year in the United States.1–3  A pulmonary embolism is an obstruction of the pulmonary artery or one of its branches by a thrombus. The signs and symptoms range from massive pulmonary embolism that results in unstable hemodynamic status to a small peripheral embolus that can be asymptomatic. To aid in the delineation of the types of pulmonary embolism, the American Heart Association has proposed several definitions (Table 1). These definitions have been used in clinical trials and practice guidelines to help stratify patients and aid in treatment selection.

Approximately 44% of patients who have pulmonary embolism have a confirmed deep vein thrombosis. The pathogenesis of venous thromboembolism can be explained on...

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