Purpose: In patients with chronic thromboembolic pulmonary hypertension (CTEPH), partial pressure of carbon dioxide(PCO2) at rest and exercise correlated with severity of CTEPH and reflect the abnormality of ventilatory efficiency by increase in physiologic alveolar dead space (AVDSf). Aim was to determine the value of delta in PCO2 and AVDSf as prognostic marker after pulmonary endarterectomy (PEA). Methods: Between 2013 and 2020, 51 patients undergoing PEA with 2-year follow-up time were retrospectively analyzed including cardiopulmonary exercise testing and hemodynamic measurements before and 1 year after PEA. Results: PCO2 before PEA measured during induction are lower vs at the end of PEA (4.47 vs 5.66, p=0.000) and at postoperative day 1 (POD1) (4.47 vs 4.82;p=0.000). Delta PCO2 (1.183) and delta pCO2 between the end of surgery and POD 1 (0.354) correlates with postoperative NYHA and mPAP-decrease at 1-year (p=0.19;p=0.00;p=0.000;p=0,000, respectively). PEA resulted in increase of Vo2max (17.68 vs 13.47;p=0.000), oxygen uptake at aerobic threshold (12.92 vs 10.03;p=0.001), mPAP-decrease at 1-year (26.37vs 40.22;p=0.000), PVR (3.193 vs 6.13;p=0.000) and improvement of NYHA (p=0.000). AVDSf before PEA at induction (0.055) vs end of surgery (0.336) and at POD1 (mean 0.152, SD 0.15) correlated NYHA improvement and mPAP-decrease at 1-year (p=0.000;p=0.000;p=0.000 and p=0.000;p=0,000,p=0.000 respectively). Conclusion: In patients with CTEPH undergoing PEA, markers for AVDSf and ventilation/prefusion mismatch may predict outcome after surgery. If confirmed in a prospective way, these markers can support indicating start of additional treatment such as balloon angioplasty or medication.
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