Pulmonary Embolism

The answer first

Pulmonary embolism (PE) is the acute obstruction of the pulmonary arterial tree by material embolising from a systemic vein, almost always a deep vein thrombosis (DVT) of the lower limb or pelvis. Together, DVT and PE are venous thromboembolism (VTE) — one disease with two clinical faces. PE is common, lethal, and frequently missed: it kills more inpatients in the developed world than any other preventable cause. ^[1]

Three decisions determine every PE case, and they must land before the details: ^[1]

1. How likely is PE right now? Use a structured pre-test probability tool — the Wells score (PE likely greater than 4, PE unlikely 4 or less) or the Revised Geneva score (fully objective). In a clearly low-risk patient, the PERC rule can safely forego testing entirely.
2. Is this patient haemodynamically stable? Shock or sustained hypotension makes this a high-risk (massive) PE — the only category where reperfusion therapy (thrombolysis, embolectomy) is mandatory and immediately life-saving. Everyone else is first anticoagulated.
3. What is the early-death risk? Use sPESI, biomarkers (troponin, BNP), and echo to split the stable group into low (suitable for outpatient or short-stay), intermediate-low, and intermediate-high (admit, monitor for decompensation, consider rescue thrombolysis). ^[1]

Two facts govern the long view: ^[1]

• Therapeutic anticoagulation should not wait for imaging when clinical probability is high and there is no contraindication — the risk of the disease exceeds the bleeding risk of a single day of low-molecular-weight heparin.
• Duration of anticoagulation is dictated by provokability, not by the clot itself. Provoked by surgery or a transient risk factor: 3 months. Unprovoked: 3 to 6 months then reassess, often indefinite. Cancer-associated or inherited thrombophilia with recurrent events: indefinite. ^[1]

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References14ShowHide

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