Pulmonary embolism.

What it is", body: "A pulmonary embolism is a blood clot lodged in the arteries of the lung. It usually starts as a deep vein thrombosis (DVT) in the leg, breaks loose, travels through the heart, and gets stuck in the pulmonary arteries — blocking blood flow to part of the lung. Depending on the size and location of the clot, the consequence ranges from minor (a tiny clot lodged in a small artery, mild symptoms) to catastrophic (a "saddle" clot blocking both main pulmonary arteries, immediate life threat). Roughly 900,000 PE and DVT events occur in the United States each year, and PE causes 60,000–100,000 deaths annually.

How it shows up

Sudden shortness of breath is the most common symptom. Other classic features include sharp chest pain that worsens with breathing, rapid heart rate, cough (sometimes with blood), leg pain or swelling (from the source DVT), and in severe cases, dizziness, fainting, or sudden collapse. PE can also be silent — discovered incidentally on a CT scan ordered for another reason.

How we diagnose it

Suspicion is the first step. We use clinical decision tools like the Wells score to estimate the probability of PE. Low-probability patients get a D-dimer blood test; if negative, PE is effectively ruled out. Moderate or high-probability patients (and low-probability with elevated D-dimer) get a CT pulmonary angiogram (CTPA) — the imaging gold standard. Once PE is diagnosed, we assess severity with the Pulmonary Embolism Severity Index (PESI) and look for signs of right heart strain on echocardiogram or troponin. These determine whether outpatient treatment, inpatient treatment, or aggressive intervention (thrombolysis, catheter-directed therapy, surgery) is needed.

How we treat it

The mainstay is anticoagulation — direct oral anticoagulants (rivaroxaban, apixaban) for most patients, low-molecular-weight heparin for cancer-associated PE, warfarin in selected situations. Most patients are treated for 3 months minimum. Duration beyond 3 months depends on whether the PE was provoked or unprovoked. For severe PE with hemodynamic instability or massive clot burden, systemic thrombolysis or catheter-directed thrombolysis can dissolve the clot rapidly.

What you can do

• —Take your anticoagulant exactly as prescribed. Missing doses substantially increases recurrence risk.
• —Know your follow-up plan. Most patients need pulmonary or hematology follow-up to decide on duration.
• —Watch for warning signs — bleeding, or new shortness of breath or leg swelling (suggesting recurrence).
• —If you have risk factors for clots, talk to your provider about prophylaxis when those risks are active.

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