17th January 2024

Background

Epidemiology

Pulmonary embolism (PE) is the third most common cardiovascular disease, with an incidence of approximately 60-70 per 100,000 people (1). The vast majority occur provoked, with common risk factors including deep venous thrombosis (DVT) elsewhere, underlying active malignancy, prolonged immobility, recent surgery, lower limb trauma, inherited and acquired thrombophilias, use of the combined oral contraceptive pill (COCP), pregnancy and obesity.

Pathophysiology

Pulmonary embolism (PE) is a form of venous thromboembolism (VTE) affecting the pulmonary arterial system and can be either an acute or chronic problem associated with the risk factors detailed above. It most commonly occurs when emboli from elsewhere in the deep venous system travel to the pulmonary vasculature and become lodged in a pulmonary artery. This results in a ventilation-perfusion mismatch, as healthy lung tissue is insufficiently perfused with oxygenated blood and can cause progression to pulmonary infarction. Less commonly, non-thrombotic sources of emboli can arise, including air emboli, fat emboli, septic emboli and, in pregnant women, amniotic fluid emboli. In severe cases, PE can be associated with hypotension, syncope and sudden death, as pulmonary arterial pressure increases to the point where it causes right ventricular failure and compromises cardiac output.