A pulmonary embolism (PE) is a blockage in one or more of the arteries supplying the lungs, caused by a blood clot (thrombus) that has travelled from elsewhere in the body, most commonly from a deep vein thrombosis (DVT) in the leg or pelvis. When a large clot or multiple clots obstruct the pulmonary circulation, the right ventricle must work against dramatically increased resistance, and oxygenation of the blood is severely impaired.
Pulmonary embolism ranges widely in severity. Small PEs may be asymptomatic or cause only mild breathlessness and palpitations. Massive PE, in which the main pulmonary artery or both main branches are occluded, causes acute cardiovascular collapse (obstructive shock), right ventricular failure, and cardiac arrest. PE is one of the four reversible causes of cardiac arrest (along with hypoxia, tension pneumothorax, and tamponade) addressed in the ALS 4H and 4T protocol.
Risk factors for PE include prolonged immobility, major surgery, cancer, pregnancy, and inherited or acquired clotting disorders. Cardiac arrest survivors in critical care are at elevated risk due to immobility, central venous catheters, and reduced circulation; low-molecular-weight heparin (LMWH) thromboprophylaxis is routinely given to reduce this risk.
Diagnosis is by CT pulmonary angiography (CTPA), the gold standard investigation. Treatment for confirmed PE is anticoagulation to prevent clot extension and allow natural thrombolysis; in life-threatening massive PE, systemic thrombolysis (clot-dissolving drugs) or emergency surgical embolectomy may be necessary. See also: Thrombosis, Anticoagulant.
« Back to Glossary Index