Residual Pulmonary Vascular Obstruction Index Computed With Ventilation/Perfusion SPECT/CT Imaging to Predict the Risk of Venous Thromboembolism Recurrence in Patients With Pulmonary Embolism (PRONOSPECT)

Condition(s) studied

Investigational drug(s) / intervention(s)

Ventilation/Perfusion Single Photon Emission Computed Tomography (V/Q SPECT/CT): All patients will undergo a V/Q SPECT/CT scan at inclusion.

Study summary

Major risk after pulmonary embolism (PE) is recurrence, fatal in 10% of patients. Patients with PE can be stratified in 3 groups according to the risk of recurrence : very low risk, high risk or Intermediate risk. Little is known about this last group.

Anticoagulation is efficient to prevent recurrence but is currently not recommended for patient with an intermediate risk of recurrence.

Identifying risk factors of recurrent PE remains a major issue to identify sub-groups of patients who would require lifelong anticoagulation.

In 30-40% of cases, PE patients develop residual pulmonary vascular obstruction (RPVO), which has been found to be associated with an increased recurrence risk. This last observation was mostly reported in patients with unprovoked PE (patients with high risk of recurrence) and RPVO was measured using conventional planar lung scan.

In patients with an intermediate risk of recurrence, the impact of RPVO has been much less studied. In addition, the definition of RPVO was variable according to studies and correlation between RPVO burden and recurrence risk has not been clearly demonstrated. This might be explained by the inherent limitation of RPVO quantification using conventional planar imaging, which is only based on a visual estimation on 2-dimensional images.

Ventilation/Perfusion Single Photon Emission Computed Tomography (V/Q SPECT/CT) is a new method of scintigraphic image acquisition that offers the advantage of 3-dimensional imaging, enabling more accurate and reproducible quantification of RPVO.

The main hypothesis of this study is that in patients with PE at intermediate risk of recurrence, RPVO computed with V/Q SPECT/CT imaging may be an important predictor of recurrence.

Eligibility

Primary outcome measure(s)

• Symptomatic recurrent venous thromboembolism (VTE), including objectively confirmed nonfatal symptomatic PE or proximal deep vein thrombosis or fatal PE during a 24-month follow-up after inclusion in the study — From baseline to Month 24
  In case of a suspected VTE or death during follow-up, the study personnel will collect related clinical data on the electronic case report form, and prepare an adjudication file, including symptoms, clinical notes, hospital discharge summary, and results of all diagnostic tests. All suspicion of VTE recurrence will be adjudicated blindly by an independent central Clinical Events Committee. To assess the primary objective, RPVO will be defined by a perfusion mismatched defect of at least 5% of the whole lung, corresponding to a segmental defect. SPECT imaging should not be used at inclusion and should not result in proposing prolonged anticoagulation. SPECT images will be numerically stored and interpretation will be later performed independently by two nuclear medicine physicians who will be blinded to clinical history and the patient's outcome. Any difference in interpretation will be resolved by consensus.

Trial sites (13)

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