Pulmonary Embolism (PE)

How a pulmonary embolism happens

Most PEs start as a deep vein thrombosis in the leg or pelvis. Part of the clot breaks off, travels through the heart, and lodges in the pulmonary arteries. This:

• blocks blood flow to part of the lung, so less oxygen enters the blood
• raises pressure in the right side of the heart, which can strain or fail it
• can cause lung tissue to die (pulmonary infarction), causing pleuritic pain and coughing up blood

DVT and PE together are called venous thromboembolism (VTE). Rarely, emboli are made of fat (after fractures), air, amniotic fluid or tumor.

Symptoms

Symptoms depend on clot size and your overall health:

• sudden shortness of breath, at rest or with exertion
• sharp chest pain that is worse when breathing in or coughing (sharp chest pain), sometimes mimicking a heart attack
• fast heart rate and fast breathing
• cough, sometimes with blood (hemoptysis)
• lightheadedness or fainting
• anxiety or a sense of doom
• sweating
• leg pain or swelling from the source DVT

Some people, especially older adults, have only mild or vague symptoms.

Risk factors

Temporary

• surgery, particularly hip or knee replacement and major abdominal or cancer surgery
• hospital stays and immobility, including long-haul travel over about 4 hours
• leg fractures or casts
• pregnancy and the 6 weeks after birth
• estrogen-containing birth control and hormone therapy
• COVID-19 and other acute illnesses

Ongoing

• cancer and some cancer treatments
• previous DVT or PE
• inherited clotting disorders such as factor V Leiden
• antiphospholipid syndrome
• obesity, smoking, older age
• heart failure, inflammatory bowel disease, kidney disease

Diagnosis

Because symptoms overlap with heart attack, pneumonia and other conditions, doctors use a structured approach:

1. Clinical probability scores (such as Wells or PERC rules) estimate likelihood.
2. D-dimer blood test: a normal result in someone at low or moderate risk effectively rules out PE.
3. CT pulmonary angiography (CTPA): the main imaging test, showing clots in the lung arteries.
4. Ventilation-perfusion (V/Q) scan: an alternative for pregnancy or kidney problems.
5. Leg ultrasound: to look for DVT.
6. ECG, echocardiogram and blood tests (troponin, BNP) to assess heart strain and severity.

Treatment

Anticoagulants (blood thinners)

Blood thinners stop clots from growing and new ones forming while the body breaks down the existing clot.

• Direct oral anticoagulants (apixaban, rivaroxaban, dabigatran, edoxaban) are first choice for most people.
• Low molecular weight heparin injections, preferred in pregnancy and sometimes in cancer.
• Warfarin, with regular INR blood tests, for some people such as those with antiphospholipid syndrome or mechanical heart valves.

Treatment lasts at least 3 months. People whose PE had no clear trigger, or who have ongoing risk factors, may need long-term treatment. Many people with low-risk PE can be treated at home.

Severe PE

• Thrombolysis: clot-busting medicine for massive PE with low blood pressure.
• Catheter-directed therapy: removing or dissolving the clot through a catheter.
• Surgical embolectomy: rarely.
• IVC filter: a device in the main vein to catch clots, for people who cannot take blood thinners.

Complications

• death, especially with massive PE
• recurrent clots
• post-PE syndrome: persistent breathlessness and reduced exercise capacity
• chronic thromboembolic pulmonary hypertension (CTEPH): a small percentage develop high lung pressure from persistent clots; see pulmonary hypertension
• bleeding from blood thinners

Recovery

Many people feel better within days to weeks, but tiredness and breathlessness can last months. Gradually increase activity. Report bleeding, black stools, severe headaches or new breathlessness while on blood thinners. Follow-up at about 3 months reviews symptoms and decides on treatment length.

Prevention

• move around after surgery as soon as advised; use prescribed blood thinners or compression devices in hospital
• on long trips, walk every 1 to 2 hours, flex your calves and stay hydrated
• maintain a healthy weight and do not smoke
• discuss clot risk before starting estrogen-containing contraception or hormone therapy, especially with a family history

Frequently asked questions

What are the first signs of a pulmonary embolism?

The most common first signs are sudden shortness of breath and sharp chest pain that worsens with breathing. A fast heartbeat, coughing up blood, lightheadedness or fainting may also occur. A swollen, painful leg can be an earlier warning of DVT.

What causes a blood clot in the lungs?

Most pulmonary embolisms start as clots in deep leg veins that break off and travel to the lungs. Risk rises with surgery, immobility, long travel, pregnancy, estrogen, cancer, previous clots and inherited clotting disorders.

Can you survive a pulmonary embolism?

Yes. Most people who are diagnosed and treated promptly survive and recover well. Large clots that cause low blood pressure are life-threatening and need emergency treatment, which is why sudden breathlessness needs immediate care.

How long does it take to recover from a pulmonary embolism?

Many people feel much better within a few weeks, but full recovery can take several months. Blood thinners continue for at least 3 months. Persistent breathlessness after that should be checked for complications.

How long will I need blood thinners after a PE?

At least 3 months. If the PE was triggered by a temporary factor such as surgery, treatment often stops then. If there was no clear cause or risk factors persist, long-term treatment may be recommended after weighing the bleeding risk.