Pulmonary Embolism: Causes, Symptoms, Diagnosis & Treatments

Pulmonary embolism (PE) is a blood clot that blocks and stops blood flow to an artery in your lung. Usually, the clot starts in a vein in your leg or pelvis. It breaks free and moves through your bloodstream until it reaches your lungs, where it gets stuck in a blood vessel and obstructs the passage of blood.

Pulmonary embolism can damage part of the lung due to restricted blood flow, decreased oxygen levels in the blood, and effects on other organs.

Pulmonary embolism can be life-threatening. However, prompt treatment greatly reduces the risk of death. Taking measures to prevent blood clots in your legs will help protect you against pulmonary embolism.

Symptoms of pulmonary embolism

Symptoms of a PE depend on the size of the clot and where it gets stuck in the lung. The most common symptom of a PE is shortness of breath. This may be gradual or sudden. Other symptoms include:

• anxiety
• clammy or bluish skin
• chest pain that may extend into your arm, jaw, neck, and shoulder
• fainting
• irregular heartbeat
• lightheadedness
• rapid breathing
• rapid heartbeat
• spitting up blood
• weak pulse

If you notice one or more of these symptoms, especially shortness of breath, you should seek medical attention immediately.

Causes of pulmonary embolism

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 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.

Blood clots in the deep veins of the body can have several different causes, including:

• Injury or damage. Injuries like bone fractures or muscle tears can cause damage to blood vessels, leading to clots.
• Inactivity. During long periods of inactivity, gravity causes blood to collect in the lowest areas of your body, which may lead to a blood clot. This could occur if you’re sitting for a lengthy trip or if you’re lying in bed recovering from an illness.
• Medical conditions. Some health conditions cause blood to clot easily, which can lead to PE. Treatments that involve surgery often lead to short-term bed rest or limited movement, which can make clotting more likely. Also, certain medical therapies for cancer can have side effects such as clotting in the blood. This puts you at risk for DVT and PE.

Occasionally, blockages in the blood vessels are caused by substances other than blood clots, such as:

• Fat from the inside of a broken long bone
• Part of a tumor
• Air bubbles

You can also read: Symptoms & Causes of Deep Vein Thrombosis

Risk factors of pulmonary embolism

Many conditions and situations raise your risk for a pulmonary embolism. What they share in common is that they make your blood more likely to clot when it shouldn’t. Examples include:

• Surgery: Major surgery, especially on your hips or legs, raises your risk for a PE. Bed rest as you recover makes blood more likely to pool. Plus, other factors, like general anesthesia and trauma to blood vessels, can raise the risk of clots forming.
• Hospital stay: Even if you don’t have surgery, a hospital stay for any reason raises your PE risk, especially if it’s for longer than three days. This is because you’re not moving around as much. Your care team will take steps to lower your risk.
• Thrombophilia (blood clotting disorders):This is a group of conditions that cause your body to make too many clots or have trouble breaking down old ones. Factor V Leiden, prothrombin mutations and antiphospholipid syndrome are common risk factors for PE.
• Pregnancy: Your risk for DVT or PE goes up while you’re pregnant and for a few months after you give birth. This is partly due to hormone changes.
• Hormone-based medications: Certain forms of oral contraception and hormone-replacement therapy can raise your risk for blood clots that lead to PE. If you’re on these meds, it’s important to talk to your provider about the risks and how to manage them.
• Long periods of sitting still: This includes everything from sitting at your work desk all day to taking a long car or plane ride. You’re more likely to get blood clots if you sit for a long time without moving your legs.
• Cancer: Having cancer or receiving cancer treatment raises your risk for PE. Together, DVT and PE are the second leading cause of death among people with cancer, behind cancer itself.
• Other medical conditions: Any condition that makes your blood more likely to clot raises your risk of PE. Some of these are temporary, like a severe COVID-19 infection. Others last longer, like kidney disease, heart failure, autoimmune diseases and atrial fibrillation.

Complications of pulmonary embolism

A pulmonary embolism can be life-threatening. About one-third of people with an undiagnosed and untreated pulmonary embolism don’t survive. When the condition is diagnosed and treated promptly, however, that number drops dramatically. But it can also be fatal despite treatment.

A pulmonary embolism disrupts normal blood flow through your lungs. It’s a medical emergency because it can lead to:

• Sudden stopping of your heart (cardiac arrest)
• Dangerous drop in blood flow to your body (obstructive shock)
• Lung tissue death from lack of blood flow (pulmonary infarction)

Pulmonary embolisms also can lead to pulmonary hypertension, a condition in which the blood pressure in the lungs and in the right side of the heart is too high. When you have blockages in the arteries inside your lungs, your heart must work harder to push blood through those vessels. This increases blood pressure and eventually weakens your heart.

In rare cases, small clots called emboli remain in the lungs and scarring develops in the pulmonary arteries over time. This restricts blood flow and results in chronic pulmonary hypertension.

You can also read: Risk factors & Complications of High Blood Pressure

Prevention of pulmonary embolism

Preventing clots in the deep veins in your legs will help prevent pulmonary embolisms. It’s not always easy to prevent PE. But there’s a lot you can do to lower your risk:

• Don’t sit still for too long at once. Whether you’re working a desk job or taking a long flight, keep moving. Flex your ankles or stand up and stretch every 30 minutes. This helps keep blood from pooling in your leg veins, which can lead to blood clots or PE.
• Compression stockings. Compression stockings steadily squeeze the legs, helping veins and leg muscles move blood more efficiently. They offer a safe, simple and inexpensive way to keep blood from pooling in the legs during and after surgery.
• Leg elevation. Elevating your legs when possible and during the night can be very effective. Raise the bottom of your bed 4 to 6 inches (10 to 15 cm) with blocks or books.
• Physical activity. Moving as soon as possible after surgery can help prevent pulmonary embolism and hasten recovery overall. This is one of the main reasons your nurse may push you to get up, even on your day of surgery, and walk despite pain at the site of your surgical incision.
• Blood thinners (anticoagulants). These medicines are often given to people at risk of clots before and after surgery. Also, they’re often given to people admitted to the hospital with certain medical conditions, such as heart attack, stroke or complications of cancer.
• Pneumatic compression. This treatment uses thigh-high or calf-high cuffs that automatically inflate with air and deflate every few minutes. This massages and squeezes the veins in your legs and improves blood flow.

Diagnosis of pulmonary embolism

PE has a wide variety of characteristics, ranging from no symptoms to sudden death. The most common presenting symptom is shortness of breath followed by chest pain and cough. However, many people with PE have mild or nonspecific symptoms or are asymptomatic, including people with a large PE. When you talk with a doctor about your symptoms, they’ll ask about your overall health and any preexisting conditions you may have. Your doctor will typically perform one or more of the following tests to discover the cause of your symptoms:

• Chest X-ray. This is a standard, noninvasive test that lets a doctor see your heart and lungs to look for other obvious causes of your symptoms. A PE can not be diagnosed with this test. The most common finding of a PE on a chest X-ray is “normal.”
• Electrocardiography (ECG). An ECG measures your heart’s electrical activity. A PE can not be diagnosed on an ECG. This test will check for other causes of chest pain.
• Computed tomography pulmonary angiography (CTPA). This test is the first-choice diagnostic imaging method because it’s sensitive and specific for the diagnosis of PE. However, it requires the use of intravenous (IV) contrast. Therefore, people with kidney problems will likely not be able to have this test because contrast may cause or worsen kidney disease. When a CTPA can not be performed, the doctor may instead consider a VQ scan to diagnose a PE.
• Ventilation/perfusion scan (VQ). A VQ scan is carried out in two parts. In the first part, radioactive material is breathed in, and pictures are taken to look at the airflow in your lungs. In the second part, a different radioactive material is injected into a vein in your arm, and more images are taken to see the blood flow in your lungs. This is mostly reserved for when:
  • you can not receive a CTPA
  • the results of the CPTA were inconclusive
  • more testing is needed
• Magnetic resonance pulmonary angiography (MRPA). This is not recommended as a first-line test for diagnosing PE, but it may be an imaging option to diagnose PE in people who can neither receive a CTPA nor a VQ scan. Potential advantages of MRPA are that no ionizing radiation is involved, and the examination can be combined with MR venography in the same sitting to look for DVT.
• Venography. A venogram is an invasive test that is rarely used for the diagnosis of only a DVT. This is a specialized X-ray of the veins in your legs and also requires the use of contrast.
• Pulmonary angiography. A pulmonary angiography is an invasive test that’s rarely used to diagnose an acute PE. It involves making a small incision so a doctor can guide specialized tools through your veins. The doctor will use contrast to see the blood vessels in the lung.
• Duplex venous ultrasound. This is a practical and noninvasive test to only diagnose a DVT. It’s important to remember that you can still have a PE even if the ultrasound is negative for a DVT. This test uses radio waves to visualize the blood flow and check for blood clots in your legs.
• D-dimer test. This is a type of blood test used to screen for signs of a PE or DVT based on the your probability of having a clot. A doctor can not make a diagnosis based on this blood test. If the result is positive, the doctor must confirm the diagnosis with the appropriate imaging method.

Acute PE, a blockage in the lung artery, often from a blood clot, is a common and sometimes fatal disease. When you’re evaluated for a PE, it’s often important for the evaluation to be efficient and avoid unnecessary testing so you can start therapy quickly.

You can also read: Prevention & Diagnosis of Stroke

Treatments of pulmonary embolism

Treatment of a pulmonary embolism focuses on keeping the blood clot from getting bigger and preventing new clots from forming. Prompt treatment is essential to prevent serious complications or death. Treatment can include medicines, surgery and other procedures, and ongoing care.

Medications

Medicines include different types of blood thinners and clot dissolvers.

• Blood thinners (Anticoagulants). These blood-thinning medicines called anticoagulants prevent existing clots from getting bigger and new clots from forming while your body works to break up the clots. Heparin is a frequently used anticoagulant that can be given through a vein or injected under the skin. It acts quickly and is often given along with an oral anticoagulant, such as warfarin (Jantovin), until the oral medicine becomes effective. This can take several days. Newer oral anticoagulants work more quickly and have fewer interactions with other medicines. Some have the advantage of being given by mouth until they’re effective, without the need for heparin. However, all anticoagulants have side effects, and bleeding is the most common.
• Clot dissolvers (thrombolytics). While clots usually dissolve on their own, sometimes thrombolytics — medicines that dissolve clots — given through a vein can dissolve clots quickly. Because these clot-busting medicines can cause sudden and severe bleeding, they usually are reserved for life-threatening situations.

Medical procedures/Surgery

• Embolectomy (Clot removal). If you have a large, life-threatening clot in your lung, your health care provider may remove it using a thin, flexible catheter threaded through your blood vessels.
• Inferior vena cava filter (IVC) (Vein filter). A catheter also can be used to position a filter in the body’s main vein, the inferior vena cava, that leads from your legs to the right side of your heart. The filter can help keep clots from going to your lungs. This procedure is usually only used for people who can’t take anticoagulant drugs or those who get blood clots even with the use of anticoagulants. Some filters can be removed when no longer needed.

You can also read: Treatments of High Cholesterol

Conclusion

A pulmonary embolism occurs when a blood clot reaches the lungs. These blood clots often come from deep vein thrombosis, which can result from damage to bone and muscle or from long periods of inactivity. Many times the exact cause of a DVT or PE is unknown despite a thorough evaluation.

A PE can be very dangerous, so it’s important to contact a medical professional if you’re experiencing symptoms such as chest pain, spitting up blood, and fainting. 

A doctor will typically prescribe medications that thin the blood and, in certain cases, use medications that break up blood clots. Minimally invasive interventional procedures and surgery may be required in some instances.