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Taking peoplePhase 4

Watchful waiting versus blood thinners for small lung blood clots

Compares rivaroxaban with a placebo in low-risk adults with small pulmonary embolism.

Key facts

Who runs it
Drahomir Aujesky
Where
Belgium, Canada, France, Netherlands, and Switzerland40 sites in 5 countriesChoose a country to see its sites
Registry title
Clinical Surveillance vs. Anticoagulation for Low-risk Patients With Isolated Subsegmental Pulmonary Embolism
Status
Recruiting
Phase
Phase 4
People taking part
276 people, planned
Started
15 May 2020
Expected to end
May 2028
Type of study
Interventional, 2 groupsOne group gets an existing treatment, for comparison.
Treatments tested
  • Rivaroxaban
  • Placebo
Record updated
22 May 2026

Who can take part

AI summary

From the trial's eligibility criteria. Machine-read from the registry text on this page, so it can be wrong. The registry text below and the trial team decide who can take part.

The trial is looking for adults with a small blood clot only in the smallest lung arteries (isolated subsegmental pulmonary embolism) and a low risk. It compares close check-ups without blood thinners to treatment with rivaroxaban.

Age
18 years or older
Sex
All sexes
Disease stage
Isolated subsegmental pulmonary embolism, with or without symptoms, confirmed by an objective test. Patients must be stable.
Earlier treatment
People who have had full-dose blood thinner treatment for more than 72 hours at screening cannot join.

Main reasons for not taking part

  • A deep vein clot in the leg or upper arm (subclavian vein or above)
  • Active cancer treated in the last 6 months
  • Unstable condition: systolic blood pressure <100 mm Hg or oxygen saturation <92% at room air
  • Active bleeding or high bleeding risk, severe kidney failure (creatinine clearance <30ml/min) or severe liver disease (Child-Pugh B or C)
  • Pregnancy, breastfeeding, or needing blood thinners for another reason

The registry criteria, word for word

Show all 19 criteriaShow less

Who can take part

  • Informed Consent as documented by signature
  • Age ≥18 years
  • Objective diagnosis of symptomatic or asymptomatic isolated SSPE

Who cannot take part

  • Active cancer, defined as cancer treated with surgery, chemotherapy, radiotherapy, or palliative care during the last 6 months
  • ≥1 prior episode of unprovoked VTE (absence of a transient or permanent risk factor)
  • Concomitant use of strong CYP3A4 inhibitors or strong CYP3A4 inducers
  • Hospitalized for >72 hours prior to the diagnosis of isolated SSP (hospital-acquired VTE)
  • Prior enrolment in this trial
  • Presence of leg deep vein thrombosis (DVT) or upper extremity DVT (subclavian vein or above)
  • Active bleeding or at high risk of bleeding
  • Severe liver insufficiency (Child-Pugh B or C)
  • Known hypersensitivity to rivaroxaban
  • Severe renal failure (creatinine clearance <30ml/min)
  • Clinical instability (systolic blood pressure <100 mm Hg or arterial Oxygen saturation <92% at ambient air) at the time of presentation
  • Need for therapeutic anticoagulation for another reason
  • Therapeutic anticoagulation for >72 hours for any reason at the time of screening
  • Known pregnancy or breast feeding (pregnancy test to be performed for women of childbearing potential)
  • Lack of safe contraception in women of childbearing potential
  • Refusal or inability to provide informed consent

This trial has no sites in United States.

It has sites in 5 countries. Choose a country to see its sites.

About the trial

What the trial wants to find out

The clinical significance of pulmonary embolism (PE) limited to the subsegmental pulmonary arteries, so called isolated subsegmental pulmonary embolism (SSPE), remains controversial. Whether isolated SSPE represents "true" PE, a clinically more benign form of PE, a physiologic lung clearing process, or a false positive result (artifact) is currently unclear and hence, whether patients with isolated SSPE benefit from anticoagulant treatment is uncertain. Despite growing evidence from observational studies that withholding anticoagulation may be a safe option in selected patients with isolated SSPE (i.e., those without concomitant deep vein thrombosis, cancer, etc.), most patients with isolated SSPE receive anticoagulant treatment, which is associated with an increased risk of bleeding. The overall objective of the randomized controlled SAFE-SSPE trial is to evaluate the efficacy and safety of clinical surveillance without anticoagulation compared to anticoagulation treatment in low-risk patients with isolated SSPE.

The 2 groups in the trial

  • AnticoagulationExisting treatment, for comparison

    Patients in the anticoagulation group will receive rivaroxaban 15 mg twice daily for the first 21 days, followed by 20 mg once daily for an overall treatment duration of 90 days.

    Treatment: Rivaroxaban

  • No anticoagulationPlacebo, for comparison

    Patients in the group without anticoagulation will receive placebo twice daily for the first 21 days, followed by one tablet daily for an overall treatment duration of 90 days.

    Treatment: Placebo

Questions to ask the study team

  1. How often do I need to come in, and for how long each time?
  2. Are travel costs paid?
  3. Can I keep my own doctor?
  4. What happens if I want to stop?

Contact the study team: see the registry record → Contacts and Locations

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Data and sources

Registry record
Listed on ClinicalTrials.gov and on the EU's official list of trials (CTIS).
Official title
Clinical Surveillance vs. Anticoagulation for Low-risk Patients With Isolated Subsegmental Pulmonary Embolism: a Multicenter Randomized Placebo-controlled Non-inferiority Trial
Plain-language title
Watchful waiting versus blood thinners for small lung blood clotsGenerated from the registry record. The registry title is the official one.
AI summary
From the trial's eligibility criteria. Read by machine on 15 November 2026.
Record updated
22 May 2026