A pulmonary embolism (PE) happens when a blood clot disrupts blood flow in your lungs. While its exact prevalence is unknown, studies estimate that PE impacts 39 to 115 per 100,000 people each year.

Pulmonary embolisms are categorized based on risk. A submassive PE is at an intermediate risk level.

It’s difficult to define exactly what a submassive PE is because doctors must consider many factors when assessing risk. Groups like the American Heart Association, American College of Chest Physicians, and European Society of Cardiology all have different definitions and guidelines.

Below, we’ll detail submassive (intermediate risk) PEs, what causes them, and how doctors diagnose and treat them.

A submassive PE is an intermediate risk type of PE. Let’s explore what that means.

Hemodynamic stability

A submassive PE is hemodynamically stable. This means that a person’s heart rate and blood pressure remain steady.

More severe PEs are characterized by hemodynamic instability. In those situations, a person’s heartbeat can be irregular, and their blood pressure decreases.

Right ventricular dysfunction

Another feature of submassive PE is right ventricular dysfunction (RVD). The right ventricle is the chamber of the heart that sends blood with low oxygen into the lungs to receive fresh oxygen.

While the right ventricle can accommodate large amounts of blood, it’s not built to deal with high levels of pressure. When a PE disrupts blood flow in the lungs, it can lead to an increase in pressure.

When this happens, the right ventricle has to work harder to pump blood into the lungs. This can lead to the right ventricle not functioning as it should, causing serious problems for the heart and its ability to pump blood.

High troponins

Elevated troponin levels are another potential finding in submassive PE. Troponins are proteins that are released when damage to the heart has occurred.

Comparison chart

The table below compares the characteristics of each type of PE.

*According to the American Heart Association’s definition, in addition to being hemodynamically stable, a submassive PE has either RVD or high troponin levels. It’s also possible for both of these findings to be present.

A PE happens when a blood clot disrupts blood flow in your lungs. Clots typically form in response to an injury, although other risk factors play an important role.

Most PEs develop from a blood clot that forms in the deep veins, typically in the leg. In some cases, part of this clot can break off and travel to the lungs, where it ends up blocking an artery.

The symptoms of a submassive PE may include:

Seek emergency care

All PEs are medical emergencies that require prompt treatment. Call emergency services or go to the emergency room if you have unexplained shortness of breath or sudden chest pain.

In addition to getting your medical history and doing a physical examination, your doctor can use the following tests to help make a diagnosis of submassive PE:

  • Chest X-ray. Your doctor may initially take a chest X-ray to look at your heart and lungs to see if there are any obvious explanations for your symptoms. However, with PE, most chest X-rays appear typical.
  • Electrocardiogram (EKG). An EKG measures the electrical activity in your heart. Certain EKG changes can show how much strain a PE is putting on your heart. It can also help your doctor rule out other conditions that can cause chest pain.
  • D-dimer test. The D-dimer test looks for a protein that’s made when a blood clot dissolves in your body. High levels can indicate a problem with blood clots.
  • Troponin test. The troponin test looks for increased troponin levels in a sample of blood.
  • Arterial blood gas (ABG). The ABG test uses a blood sample from an artery. It measures oxygen and carbon dioxide levels in the blood to give your doctor an idea of how well your lungs are working.
  • CT angiography. CT angiography uses a special dye and CT scan technology to generate pictures of the blood vessels in your chest. This can help your doctor see if a blood clot is present.
  • Ventilation-perfusion (VQ) scan. A VQ scan uses radioactive material to assess both the airflow and blood flow in your lungs.
  • Echocardiogram. An echocardiogram uses ultrasound technology to visualize the chambers of your heart. Your doctor can use it to check for signs of RVD.

There are a few different treatment options available for submassive PE. The type of treatment you receive can depend on the severity of your PE.

PE severity is usually estimated using the Pulmonary Embolism Severity Index (PESI). This is a points-based system in which a higher score suggests a higher PE severity and less favorable outlook. It takes the following factors into account:

Now let’s look at treatment options for submassive PE.


One of the main treatments for submassive PE is anticoagulant therapy. Anticoagulant drugs are also called blood thinners.

These drugs interfere with proteins that are important for clotting. Heparin is an example of an anticoagulant drug that doctors may use to treat submassive PE.

Systemic thrombolytic therapy

Another potential treatment option is systemic thrombolytic therapy. Thrombolytic drugs work to dissolve clots quickly. However, their use with submassive PE is controversial, according to a 2019 consensus paper.

A 2014 study investigated systemic thrombolytic therapy in submassive PE. Overall, it found that while systemic thrombolytic therapy helped keep participants’ conditions from worsening, it also increased the risk of serious bleeding and stroke.

As such, a doctor must carefully weigh the risks and benefits of systemic thrombolytic therapy for submassive PE.

Generally, doctors may consider low dose thrombolytic therapy for people with submassive PE who are at low risk of bleeding and whose condition is worsening.

Catheter-directed thrombolysis

A catheter is a thin, flexible tube inserted into blood vessels. In catheter-directed thrombolysis, doctors use a catheter to deliver low doses of thrombolytic drugs at the location of the PE.


An embolectomy involves removing the blood clot from the body. Doctors can do this either using a catheter or through a surgical procedure.

In addition to being a life threatening condition, submassive PE can lead to a variety of complications:

  • Repeat events. If you’ve had a PE, you may be at risk of another serious blood clot event. In fact, 1 in 3 people with PE or deep vein thrombosis (DVT) has a repeat event within the next 10 years.
  • Post-PE syndrome. Post-PE syndrome refers to persistent symptoms like shortness of breath, difficulty exercising, and reduced quality of life after PE.
  • Pulmonary hypertension. Your pulmonary arteries lead from your heart to your lungs. Pulmonary hypertension is when the blood pressure in your pulmonary arteries is too high. It can lead to heart failure.
  • Chronic thromboembolic pulmonary hypertension (CTEPH). CTEPH is a specific type of pulmonary hypertension. It happens when the blood pressure in your pulmonary arteries is too high due to the presence of blood clots.

As you recover from a submassive PE, your doctor will want to regularly monitor your condition. This can help prevent a repeat event and detect and address other complications, like pulmonary hypertension.

The overall mortality rate for PE can be up to 30 percent if it’s left untreated. However, with timely medical treatment, the mortality rate drops to 8 percent. The exact mortality rate for submassive PE is still unclear.

A 2016 study divided people with PE into four risk categories:

  • high
  • intermediate-high
  • intermediate-low
  • low

The researchers found that the mortality rate for intermediate-high and intermediate-low PE was 7.7 and 6.0 percent, respectively.

Both RVD and troponin levels can contribute to the outlook for submassive PE. Worsening RVD, high troponin levels, or both generally point toward a less favorable outlook.

Studies have also looked into the rate of complications after a submassive PE. For example, a 2017 study looked at the long-term outlook in people with submassive PE treated with systemic thrombolytic therapy.

The researchers found that 36 percent of the participants had persistent symptoms like shortness of breath. CTEPH was also seen, but only in 2.1 percent of participants.

Several things can increase your risk of PE. These include:

Remember that having risk factors for submassive PE doesn’t mean that you’ll experience one in the future. It just means that you’re at an increased risk compared with people without any risk factors.

There are things you can do to help lower your risk of experiencing a PE:

  • Move around. Try to avoid being immobile for long periods of time. For example:
    • Be as active as is appropriate following a period of bed rest, such as after an injury, surgery, or illness.
    • Stop and walk around every couple of hours when you’re on a long trip.
    • If you’re sitting for a long period of time and cannot get up, exercise your legs by tightening and relaxing your leg muscles or raising and lowering your heels off the floor.
  • Make health-promoting lifestyle choices. Aiming to live a balanced lifestyle can reduce your risk of blood clots and other health conditions. Try to:
    • Eat a balanced, nutritious diet.
    • Reduce your stress levels, when possible.
    • Get enough sleep each night.
    • Quit smoking, if you smoke.
  • Manage other health conditions. If you have health conditions, such as obesity or heart disease, that increase your risk of blood clots, make sure you’re taking steps to manage them.
  • Ask a doctor about preventive measures. If you’re at a higher risk of blood clots, talk with a doctor about preventive options like compression stockings or blood-thinning medications.

A submassive PE is an intermediate risk PE. People with this type of PE have stable blood pressure and heart rate but have RVD, high troponin levels, or both.

Any type of PE is a medical emergency, and outlook greatly improves with timely treatment. Seek care immediately if you have unexplained shortness of breath or chest pain that comes on suddenly.

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