Supplementary Material for: Cardiopulmonary Exercise Testing to Detect Chronic Thromboembolic Pulmonary Hypertension in Patients with Normal Echocardiography

Background: Chronic thromboembolic pulmonary hypertension (CTEPH) is a serious complication of pulmonary embolism (PE). Taking into account the reported incidence of CTEPH after acute PE, the number of patients with undiagnosed CTEPH may be high. Objectives: We aimed to determine if cardiopulmonary exercise testing (CPET) could serve as complementary tool in the diagnosis of CTEPH and can detect CTEPH in patients with normal echocardiography. Methods: At diagnosis, we analyzed the data of CPET parameters in 42 patients with proven CTEPH and 51 controls, and evaluated the performance of two scores. Results: VE/VCO₂ slope, EQO₂, EQCO₂, P(A-a)O₂, end-tidal partial pressure of CO₂ at anaerobic threshold (PETCO₂) and capillary to end-tidal carbon dioxide gradient [P(c-ET)CO₂] were significantly different between patients with CTEPH and controls (p < 0.001). P(c-ET)CO₂ was the single parameter with the highest sensitivity (85.7%) and specificity (88.2%). A score combining VE/VCO₂ slope, P(A-a)O₂, P(c-ET)CO₂, PETCO₂ [4-parameter-CPET (4-P-CPET) score] reached a sensitivity of 83.3% and a specificity of 92.2% after cross-validation. In 42 patients with CTEPH, echocardiography identified PH in 29 patients (69%), but it was normal in 13 patients (31%). All patients with normal or unmeasurable right ventricular systolic pressure had a pathological CPET. Twelve of the 13 patients (92%) were detected by both CPET scores. Conclusion: CPET is a useful noninvasive diagnostic tool for the detection of CTEPH in patients with suspected PH but normal echocardiography. The 4-P-CPET score provides a high sensitivity with the highest specificity.