Late Breaking Abstract - Value of planar V/Q scan and V/Q SPECT in diagnosing chronic thromboembolic pulmonary hypertension: head to head comparison with pulmonary angiography

Aims: Ventilation/perfusion (V/Q) scan is recommended to exclude chronic thromboembolic pulmonary hypertension (CTEPH) in the diagnostic algorithm of PH. Difference in value of planar V/Q and V/Q SPECT for CTEPH for diagnosing CTEPH is not clear. We aimed to prospectively compare the diagnostic performance of planar V/Q and V/Q SPECT combined with lose-dose CT (LDCT) using pulmonary angiography as gold standard. Methods: Consecutive patients with suspected PH were referred to perform V/Q scan. PH due to left heart diseases or lung diseases were excluded. 285 patients underwent planar V/Q and V/Q SPECT combined with LDCT. Patients who failed to perform right heart catheterization or pulmonary angiography and those with mean pulmonary artery pressure (mPAP) < 25mmHg were excluded. The number of eligible patients was 209. Interpretation of V/Q images and diagnosis of pulmonary embolism was made according to 2009 EANM guidelines. Results: Sixty-three PH patients were confirmed with CTEPH by pulmonary angiography. There was no non-diagnostic decision during V/Q interpretation. Planar V/Q had a sensitivity of 92.1%, a specificity of 90.4%, a positive predictive value (PPV) of 80.6% and a negative predictive value (NPV) of 96.4%. V/Q SPECT had a sensitivity of 92.1%, a specificity of 88.4%, a PPV of 77.3% and an NPV of 96.3%. When LDCT was added, sensitivity was 93.7%, specificity was 88.4%, PPV was 77.6% and NPV was 97.0%. Sensitivity was 93.7%, specificity was 87.7%, PPV was 76.6% and NPV was 97.0% when perfusion SPECT with LDCT was applied. Conclusions: In the setting of PH, planar V/Q has comparable diagnostic performance compared to V/Q SPECT.