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)

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

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.

Inclusion Criteria:

• Patients ≥ 18 years,
• who experienced an objectively proven PE,
• who have been treated initially with anticoagulant therapy for 3 to 6 uninterrupted months (180 - 210 days) and for whom anticoagulation will not be prolonged.

Exclusion Criteria:

• Unwilling or unable to give written informed consent (protected adults, under tutorship or curatorship)

• Patients deprived of their liberty by a judicial or administrative decision, patients undergoing psychiatric care by virtue of Articles L. 3212-1 and L. 3213-1 who are not covered by the provisions of Article L. 1121-8 and patients admitted to a health or social establishment for purposes other than research

• No Social security affiliation

• Isolated DVT

• Pregnant women and parturients

• Other indication for anticoagulant therapy (e.g. atrial fibrillation, mechanic valve)

• Life expectancy < 6 months

• Any patients for whom there is a strong indication to treat longer than 6 months:

  • PE provoked by a major persistent factor (e.g. cancer)
  • Recurrent unprovoked PE

PE provoked by a major transient risk factor (e.g. surgery with general anesthesia for greater than 30 min, confined to bed in hospital for at least 3 days with an acute illness, cesarean section)

AND none of the following persistent factors :

• BMI ≥ 30
• Chronic respiratory disease
• Chronic inflammatory disease (e.g., ulcerative colitis, rheumatoid arthritis, etc.)
• Hepatocellular insufficiency
• Renal insufficiency with creatinine clearance < 60 mL/min
• Chronic or persistent immobilization