A pulmonary embolism (PE) is a serious medical condition that occurs when one of the pulmonary arteries in the lungs suddenly becomes blocked. If the blood clot is large enough, it can obstruct the flow of blood to the lungs which can be life-threatening. While obtaining prompt medical attention can greatly improve your chances for survival, the best way to protect yourself against pulmonary embolism is through prevention.
Causes of Pulmonary Embolism
PE is usually caused by a blood clot in the deep veins of the leg that breaks loose and travels through the circulatory system to the lungs. This condition is known as deep vein thrombosis, or DVT. Sometimes, blood clots form in a vein that’s close to the surface of your skin. This is known as superficial venous thrombosis and seldom leads to pulmonary embolism. In rare cases, other substances – small masses of infectious material, tumors, air bubbles or fat – can block the artery and lead to pulmonary embolism.1
Symptoms of Pulmonary Embolism
Symptoms of pulmonary embolism include:
- Shortness of breath that may come on suddenly
- Sudden sharp chest pain that may worsen with deep breathing and/or coughing
- Fast heart beat
- Fast breathing
- Excessive sweating
- Increased anxiety
- Coughing up blood or pink, frothy mucus
- Signs of shock (inability to answer questions, losing consciousness, feeling very dizzy or lightheaded, feeling very week or having trouble standing up, confusion, restlessness, being fearful).
The symptoms of pulmonary embolism often occur with, or may mimic other conditions such as heart attack, asthma, pneumonia – even a panic attack. Some people may not have any symptoms at all. This makes it difficult to diagnose. Sometimes, your symptoms may be related to DVT, and may include swelling, pain, tenderness, increased warmth and redness or discolored skin of the affected leg.1
Risk Factors for Pulmonary Embolism
Although anyone can get a PE, there are certain factors that place you at greater risk for its development. These include:
- Prolonged bed rest or inactivity, including taking long trips in a car or airplane
- The use of birth control pills
- Recent surgery, including heart surgery
- Before, during, and after pregnancy
- Having cancer, stroke or heart attack
- Hip or femur fractures
- Previous DVT
Diagnosis of Pulmonary Embolism
Although it’s important for someone with a PE to be examined by a doctor, a clinical assessment alone is often unreliable and the consequences of being misdiagnosed can be serious, even fatal. After your doctor performs a thorough physical exam which involves asking you questions about your medical history, the following tests may be ordered to help confirm or rule out a diagnosis of PE:1
- D-dimer blood test – measures a substance in the blood that’s released when a blood clot breaks up. D-dimer levels are usually elevated in people with PE.
- Other blood tests – including blood tests that check for inherited conditions that put you at greater risk for blood clots. Additionally, because a blood clot in your lungs can lower the amount of oxygen that’s in your blood, a blood test that measures the amount of oxygen and carbon dioxide in your blood may also be ordered.
- Ventilation/perfusion (VQ) lung scan – a nuclear medicine scan that uses a radioactive substance to examine the flow of air (ventilation) and blood flow (perfusion) in the lungs.
- Computed topography (CT) scan – a dye is injected into a vein in your arm that makes the blood vessels in your lungs show up on an X-ray examination. This helps identify the presence of a clot.
- Pulmonary angiogram – a catheter (flexible tube) is inserted into the groin or arm and threaded through the blood vessels to your lungs. Your doctor uses the catheter to inject dye into the blood vessels. X-rays are then taken that show the flow of blood through the lungs. If a blood clot is found, your doctor may decide to remove it through the catheter or inject a medicine that will dissolve the clot.
- Additional tests – may be ordered to rule out the possible causes of your symptoms and may include an echocardiogram (uses sound waves to check heart function and detect blood clots in the lungs), an EKG (detects and records the electrical activity of the heart), chest X-ray, and chest MRI (uses radio waves and magnetic fields to provide more information about the organs and structures in your body than a simple X-ray).
Treatment of Pulmonary Embolism
The primary goals of treatment for PE are to prevent the existing blood clot from becoming larger and to keep new clots from forming. To accomplish this, doctors use medication, procedures and other therapies as follows:1
- Medication – Anticoagulants (blood thinners) are used to prevent the clot from getting larger and to keep new clots from forming. They do not dissolve blood clots that have already formed. The most common types of anticoagulant therapy involves using heparin and warfarin (Coumadin). Because heparin acts quickly and warfarin takes 2-3 days to take effect, your doctor may start you on both, then discontinue heparin once the warfarin begins to work. A newer type of blood-thinning agent – thrombin inhibitors – may be used to treat some types of blood clots in people who are unable to tolerate heparin. Thrombolytics, medications that can rapidly dissolve clots, are sometimes given in the emergency room or the hospital. Because one of the side effects of this type of medicine is sudden bleeding, they are only given in emergency, life-threatening situations.
- Procedures – your doctor may be able to remove or dissolve a clot by inserting a catheter into your groin or arm and threading it through your blood vessels until it reaches the clot. In rare occasions, surgery may have to be performed to remove a clot.
- Other therapies – if you’re unable to take blood thinners or they don’t work the way they’re supposed to, your doctor may suggest a vena cava filter, a medical device that prevents blood clots from traveling to your lungs. Graduated compression stockings, as ordered by your doctor, can also be worn on the legs to help prevent the ongoing swelling in your legs from DVT.
Prevention of Pulmonary Embolism
The first step in preventing pulmonary embolism is to know whether you’re at risk for DVT. Once you understand your risk factors, you can take the following steps to lower your risk:
- Exercise your lower leg muscles when traveling and while sitting for an extended period of time.
- After surgery or an illness that has left you bedridden, get out of bed as soon as possible and move around. Engaging in movement helps prevent blood clots from forming.
- Take blood thinners as prescribed by your doctor.
- Visit your doctor for regular checkups.
If you have signs and symptoms of DVT or PE, contact your doctor immediately or seek emergency medical care.
 National Heart, Lung and Blood Institute. Pulmonary Embolism. Last updated 8/18/16..
The Lung Association. Pulmonary Embolism: Risk Factors. Last Updated 9/8/14.
 Clive Kearon. Diagnosis of Pulmonary Embolism. CMAJ January 21, 2003 vol. 168no. 2 183-194.