what causes a pulmonary embolism
A pulmonary embolism (PE) is almost always caused by something blocking an artery in the lungs, most often a blood clot that has traveled from the leg or pelvis.
What actually causes a pulmonary embolism?
In most cases, a PE is caused by a blood clot that forms elsewhere in the body and then travels to the lungs.
- The usual source is a deep vein thrombosis (DVT) in the deep veins of the leg or pelvis.
- Less commonly, clots can come from veins in the upper body, pelvis, or even the right side of the heart.
When that clot (or other material) moves with the blood and lodges in a pulmonary artery, it blocks blood flow and becomes a pulmonary embolism.
Non‑clot causes (rarer)
Although blood clots are by far the most common cause, other things can occasionally block a lung artery:
- Air bubbles (air or gas embolism), often related to procedures or trauma.
- Fat droplets, usually after major fractures of large bones like the femur or pelvis (fat embolism).
- Pieces of a tumor breaking off and traveling in the bloodstream (tumor embolism).
These are rare compared with standard blood-clot–related PE.
Why do those clots form? (Risk factors)
Anything that makes blood more likely to clot, slows blood flow, or injures the vessel wall can lead to DVT and then PE. Common risk factors include:
- Recent surgery, especially orthopedic or major abdominal surgery.
- Long periods of immobility: long-haul flights or car trips, prolonged bed rest, hospitalization, paralysis.
- Serious illness or injury: heart attack, stroke, severe trauma, burns, fractures.
- Cancer and some cancer treatments, which can make blood more prone to clotting.
- Hormones: birth control pills, hormone replacement therapy, pregnancy, and the first weeks after childbirth (postpartum).
- Inherited or acquired clotting disorders (thrombophilias, antiphospholipid syndrome, etc.).
- Older age (especially over 60), obesity, and smoking.
- Heart and circulation problems like heart failure, atrial fibrillation, and varicose veins.
- Severe infections, including serious COVID‑19, which can increase clot risk.
People with a history of DVT or PE are at higher risk of having another event.
Mini “story” to visualize it
Imagine someone has knee replacement surgery and then is mostly lying in bed for several days. Their leg veins are not moving blood as efficiently because the muscles are not contracting. Blood flow slows, and because surgery also temporarily makes the blood more “clot-happy,” a clot forms in a deep vein in the calf.
A few days later, part of that clot breaks off, rides the bloodstream up through the veins, passes through the right side of the heart, and wedges into a branch of the pulmonary artery. Suddenly, part of the lung is cut off from blood flow: that’s a pulmonary embolism.
When to worry and what to do
Typical warning signs of a PE include sudden shortness of breath, sharp chest pain that may worsen with a deep breath, rapid heartbeat, coughing (sometimes with blood), feeling faint, or collapse.
A pulmonary embolism can be life‑threatening, so any of these symptoms—especially in someone with the risk factors above—needs emergency medical evaluation right away.
Bottom note: Information gathered from public forums or data available on the internet and portrayed here.