What is the recommended treatment for patients with intermediate Ventilation-Perfusion (VQ) scan results?

Treatment for Patients with Intermediate Ventilation-Perfusion (VQ) Scan Results

Patients with intermediate probability VQ scan results should receive therapeutic anticoagulation, as these results are considered indeterminate and require treatment in the setting of high clinical suspicion for pulmonary embolism (PE). 1

Understanding Intermediate VQ Scan Results

• Intermediate probability VQ scan results lack diagnostic utility and should be considered indeterminate 1
• Patients older than 70 years are more likely to have intermediate-probability VQ scan results 1
• In studies, approximately 30-40% of patients with intermediate probability VQ scans have pulmonary embolism 2

Initial Management Approach

• In patients with intermediate clinical suspicion of acute venous thromboembolism (VTE), treatment with parenteral anticoagulants is suggested if diagnostic test results are delayed for more than 4 hours 3
• Initial treatment options include:
  • Low-molecular-weight heparin (LMWH)
  • Fondaparinux
  • Intravenous unfractionated heparin (UFH)
  • Subcutaneous unfractionated heparin 3

Further Diagnostic Evaluation

• Additional imaging is recommended to confirm diagnosis:
  • Venous Doppler ultrasound to detect deep vein thrombosis (DVT)
  • CT pulmonary angiography (CTPA) to confirm PE 2
• Studies show that approximately 72% of intermediate probability VQ scans undergo further evaluation with venous Doppler ultrasound and/or CTPA 2
• About 39% of patients who undergo additional imaging show evidence of thromboembolic disease 2

Anticoagulation Strategy

• If PE is confirmed or clinical suspicion remains high:
  • For most patients, a direct oral anticoagulant (DOAC) is preferred over vitamin K antagonist (VKA) therapy 4, 5
  • If using VKA therapy, start it early and continue parenteral anticoagulation for at least 5 days and until the INR is ≥2.0 3
  • For cancer patients, LMWH is suggested over VKA or DOACs 6

Duration of Anticoagulation

• For first PE secondary to a major transient/reversible risk factor: discontinue anticoagulation after 3 months 4
• For unprovoked PE or PE with persistent risk factors: consider extended anticoagulation 4
• For recurrent VTE not related to a major transient risk factor: continue oral anticoagulant treatment indefinitely 4
• For patients with antiphospholipid antibody syndrome: continue oral anticoagulant treatment with a VKA indefinitely 4

Follow-up Care

• Routine re-evaluation 3-6 months after acute PE 4
• For patients on extended anticoagulation, regularly reassess:
  • Drug tolerance and adherence
  • Hepatic and renal function
  • Bleeding risk 4
• Refer symptomatic patients with mismatched perfusion defects on V/Q scan beyond 3 months to a pulmonary hypertension/CTEPH expert center 4

Important Considerations and Pitfalls

• Do not routinely use inferior vena cava filters 4
• Do not use NOACs in patients with severe renal impairment or antiphospholipid antibody syndrome 4
• In one study, no mortality or PE was found on follow-up of untreated patients with intermediate probability VQ scans who had negative additional imaging or low clinical suspicion 2
• Be aware that silent PE can occur in high-risk populations (e.g., 17% of adult Fontan patients had clinically silent PE in one study) 7