Introduction: Early identification of chronic thromboembolic pulmonary disease/pulmonary hypertension (CTED/CTEPH) is of clinical importance. VQ imaging is reliable for detection of chronic disease but poorly distinguishes CTEPH from CTED.

Aims: Utility of CPET in distinguishing CTED from CTEPH.

Methods: 57 patients with persisting symptoms after ?6 months of anticoagulation underwent CPET as part of investigations prior to referral to a tertiary PH centre. Retrospective analysis was undertaken to identify indices predictive of subsequent confirmatory CTEPH diagnosis. ROC analysis was used to assess CPET indices (identified by one way ANOVA and post hoc multiple comparisons) for discriminating CTEPH from CTED.

Results: ROCs for indices with AUC >0.8 are shown in the figure. VE/VCO₂ slope was the only parameter able to differentiate between CTEPH and CTED with an AUC 0.809 p=0.002. Sensitivity and specificity values of VE/VCO₂ slope for identification of CTEPH are shown in the table.

Conclusions: In this patient population, VE/VCO₂ slope identified ventilatory inefficiency arising from CTEPH.