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Study on Treatments for Intermediate High-Risk Pulmonary Embolism: Comparing Percutaneous Embolectomy, Ultrasound-Assisted Thrombolysis with Alteplase, and Heparin

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What is this trial about?

A plain-language summary of the goals, design and what participants do

This clinical trial is focused on studying the treatment of pulmonary embolism, a condition where one or more arteries in the lungs become blocked by a blood clot. The study is exploring three different treatment methods for patients with a specific type of this condition known as intermediate high-risk pulmonary embolism. The treatments being tested include a procedure called percutaneous embolectomy, which involves using a device to remove the clot, and a method called ultrasound-assisted low dose thrombolysis using a medication called alteplase. The third treatment option is the use of heparin, a medication that helps prevent blood clots, with the possibility of using a full dose of clot-busting drugs if needed.

The purpose of the study is to compare the effectiveness of these treatments in reducing the amount of clot in the lungs. Participants in the study will receive one of these treatments and will be monitored to see how well the treatment works in reducing the clot and improving their condition. The study will also look at other factors such as any bleeding complications, the length of hospital stay, and the overall quality of life after treatment.

Throughout the study, participants will undergo various assessments to track their progress, including tests to measure their ability to breathe and walk, as well as their overall heart function. The study aims to provide valuable information on the best treatment approach for patients with intermediate high-risk pulmonary embolism, helping to improve outcomes and quality of life for those affected by this condition.

The research process

The trial runs in 6 steps – from screening to follow-up. Each step says what happens and what the team monitors.

  1. Step 1

    Joining the trial

    Upon joining the trial, you will be assigned to one of three treatment groups. These groups are designed to test different methods for treating pulmonary embolism, a condition where blood clots block blood vessels in the lungs.

  2. Step 2

    Treatment assignment

    You may receive one of the following treatments: percutaneous embolectomy, which involves removing the clot using a special device; ultrasound-assisted low dose thrombolysis using a medication called alteplase; or heparin, a medication that helps prevent further clotting.

  3. Step 3

    Medication administration

    If assigned to the ultrasound-assisted thrombolysis group, you will receive alteplase through an infusion. This means the medication is delivered directly into your bloodstream over a period of time. The dosage and frequency will be determined by the medical team based on your specific needs.

  4. Step 4

    Monitoring and follow-up

    Throughout the trial, your health will be closely monitored. This includes regular check-ups and tests to assess the effectiveness of the treatment and to ensure your safety.

    You will be asked to report any side effects or changes in your condition. This information is crucial for evaluating the treatment's impact.

  5. Step 5

    Evaluation of outcomes

    The trial will measure several outcomes, such as the reduction of blood clots, any bleeding complications, and your overall quality of life.

    You will also undergo assessments like the six-minute walking distance test and quality of life surveys at specific intervals, such as after 3 months.

  6. Step 6

    Completion of the trial

    At the end of the trial, you will have a final evaluation to determine the overall effectiveness of the treatment you received.

    Your participation will contribute valuable information to help improve treatments for pulmonary embolism in the future.

Who can join the trial?

4 criteria

  • Must be 18 years or older.
  • Must have an intermediate high-risk pulmonary embolism as defined by the European Society of Cardiology (ESC) criteria. This means the condition is serious but not the most severe form.
  • A blood clot must be visible in the main, lobar, or segmental pulmonary arteries on a CT angiography. A CT angiography is a special scan that shows blood vessels.
  • Must have had symptoms for 14 days or less.

Who cannot join the trial?

5 criteria

  • Patients with a history of **pulmonary embolism** that is not considered acute or intermediate high-risk cannot participate. A pulmonary embolism is a blockage in one of the lung's arteries.
  • Patients who are not within the specified age range for the study are excluded. The study is open to certain age groups only.
  • Patients who are part of a vulnerable population, which means they might need special protection or care, are not eligible.
  • Patients who are not able to provide informed consent, meaning they cannot understand the study and agree to participate, are excluded.
  • Patients with medical conditions or treatments that could interfere with the study's procedures or outcomes are not allowed to join.
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Investigated drugs

The first therapy in the trial is called percutaneous embolectomy, which uses a device known as the Flow Triever® system from INARI Medical. This therapy involves a procedure where a doctor inserts a small tube into a blood vessel to physically remove blood clots from the lungs. This method is used to quickly clear the blockage and improve blood flow.

The second therapy is ultrasound-assisted thrombolysis, which uses the EKOS® system from Boston Scientific. This method combines ultrasound waves with a medication called alteplase to help dissolve blood clots in the lungs. The ultrasound waves help the medication reach the clot more effectively, making it easier to break down the clot and restore normal blood flow.

The third therapy involves the use of heparin, a medication that helps prevent new clots from forming and keeps existing clots from getting bigger. In some cases, doctors may also use a higher dose of a clot-dissolving medication to help break down the clots more quickly. This approach aims to manage the clot while reducing the risk of further complications.

What is already known about the treatment

  • Flow Triever® system

    The Flow Triever® system is a medical device used for percutaneous embolectomy, a procedure to remove blood clots from the lungs. It is currently being studied in clinical trials for its effectiveness in treating intermediate high-risk pulmonary embolism. This device is inserted through a small incision and guided to the clot, where it physically removes the blockage. It is classified as a mechanical thrombectomy device and offers a non-drug approach to treating blood clots in the lungs.

  • EKOS® system with low dose alteplase

    The EKOS® system is a catheter-based device that uses ultrasound waves to help deliver a low dose of the medication alteplase directly to blood clots in the lungs. It is being evaluated in clinical trials for its ability to treat intermediate high-risk pulmonary embolism. The ultrasound waves help the medication penetrate the clot more effectively, breaking it down to restore blood flow. This method combines mechanical and pharmacological approaches to clot removal.

  • Heparin

    Heparin is a medication administered through injection to prevent and treat blood clots. In the context of the clinical trial, it is used for patients with intermediate high-risk pulmonary embolism, with the option to switch to full-dose thrombolysis if needed. Heparin works by inhibiting certain factors in the blood that are necessary for clotting, thus preventing the formation or growth of clots. It is classified as an anticoagulant, commonly known as a blood thinner.

Investigated diseases

Pulmonary embolism – Pulmonary embolism is a condition where one or more arteries in the lungs become blocked by a blood clot. It often begins with a clot in the deep veins of the legs, known as deep vein thrombosis, which travels to the lungs. The blockage can cause difficulty breathing, chest pain, and a rapid heart rate. As the condition progresses, it can lead to decreased oxygen levels in the blood and damage to lung tissue. The severity of symptoms can vary depending on the size of the clot and the number of arteries affected. Over time, the body may dissolve the clot naturally, but in some cases, the blockage can lead to complications if not addressed.
Trial detailsLast updated 2 Oct 2026
Age18+ yearsPhasePhase IIITrial ID2024-515712-45-00Estimated enrolment210 patientsSponsorRigshospitalet

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On this site, “treatment” means an investigational medicine being studied in a clinical trial. Its safety and efficacy for the use being studied have not yet been confirmed, some participants may receive a placebo or a comparator medicine, and taking part does not guarantee any health benefit. The decision to take part is made by the doctor at the research site. This site is for information only and does not replace medical advice.

This service is not affiliated with the European Commission, the EMA, or the official CTIS system. Most information comes from publicly available international clinical-trial registries, supplemented by data from academic sites, national regulators and commercial sponsors. On this site, “treatment” and “therapy” mean a medicine being tested in a clinical trial. Its safety and effectiveness in the use being studied are not yet confirmed, some participants may receive a placebo or a comparator, and taking part does not guarantee a health benefit. The doctor at the research site decides who can take part. This site provides information, not medical advice. Certain content and visual elements on this website have been generated or enhanced using artificial intelligence (AI).