Description
A pulmonary embolism occurs when a clump of material, most often a blood clot, gets stuck in an artery in the lungs, blocking the flow of blood. Blood clots most commonly come from the deep veins of your legs, a condition known as deep vein thrombosis.
In many cases, multiple clots are involved. The portions of the lung served by each blocked artery can't get blood and may die. This is known as a pulmonary infarction. This makes it more difficult for your lungs to provide oxygen to the rest of your body.
Summary Listen
- Pulmonary embolism (PE) involves obstruction of the pulmonary artery or its branches, often by a thrombus originating from the lower extremities. Classification is based on the origin, chronicity, anatomic location, severity, and cause of the embolism. Acute PE can be asymptomatic, symptomatic, or fatal, while subacute presents 2-12 weeks after symptom onset. Chronic PE leads to pulmonary hypertension for at least 6 months after an acute event.
- Severity classification includes massive/high-risk (hemodynamic instability), submassive/intermediate-risk (right ventricular dysfunction without hypotension), and mild/low-risk PE. Chronicity and classification is important for determining treatment and estimating mortality risk. Other factors like the patient's pesi score are also considered to assess 30 day mortality risk.
- Risk factors for PE include orthopedic dysfunction (trauma, fractures, joint replacements), autoimmune conditions, cancer, immobility, blood disorders, prolonged bed rest, uncontrolled diabetes/hypertension, and advanced age. Inherited conditions like Factor V Leiden mutation, antiphospholipid antibody syndrome, and deficiencies in antithrombin III, protein C, and protein S also increase risk.
- Clinical presentation of PE varies, including chest pain, dyspnea, hemoptysis, palpitations, syncope, cyanosis, and diaphoresis. Syndromic presentations include pulmonary hemorrhage/infarction, isolated breathlessness, and circulatory collapse. Hemodynamic stability is determined by factors like cardiac arrest, need for cardiopulmonary resuscitation, obstructive shock, and persistent hypotension.
- Diagnostic evaluation begins with assessing the likelihood of PE. High likelihood prompts imaging modalities like CTPA or VQ scan. The PERC rule aids in ruling out PE in low-risk patients. D-dimer tests are useful but have limitations, particularly in elderly, pregnant, or cancer patients. ECGs may show sinus tachycardia or S1Q3T3 pattern. Chest x-rays may reveal vascular congestion or Hampton's hump. CT pulmonary angiography is the gold standard for diagnosis. Echocardiograms look for right ventricular dysfunction.
- Treatment approaches vary according to severity and risk of bleeding. Therapeutic anticoagulation is the cornerstone of treatment, typically for at least 3 months. Direct oral anticoagulants (NOACs) are preferred for outpatient treatment. For patients with active cancer, low molecular weight heparin is often the first-line treatment.
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