The prognostic relevance of oxygen uptake in inoperable chronic thromboembolic pulmonary hypertension

Patients with chronic thromboembolic pulmonary hypertension (CTEPH) present with a decreased oxygen uptake, however, the prognostic relevance of oxygen uptake (VO₂ ) in inoperable CTEPH is unknown.

Patients with inoperable CTEPH were retrospectively analyzed. All patients were assessed by means of right heart catheterisation and cardio pulmonary exercise testing in semisupine position with a 30 Watt increment step-protocol.

One-hundred and fifty-one patients (82 female (54.3%), mean age 61 ± 12.4 years) presented with a mean pulmonary arterial pressure of 40.2 ± 14.2 mmHg and pulmonary vascular resistance (PVR) of 641.9 ± 374.8 dyne∗s/cm⁵ . The peak VO₂ (mean 13.1 ± 4.5 mL∗kg^-1 ∗min^-1 ) was measured at initial referral. Over a follow-up of up to 10 years (mean 4.41 ± 2.57 years), 31 patients had died. Patients with a baseline peak VO₂  ≥ 10.7 mL∗kg^-1 ∗min^-1 [area under the receiver-operating characteristic curve (AUC) = 0.728, P = 0.001] had better survival than those with a peak VO₂  ≤ 10.7 mL∗kg^-1 ∗min^-1 using Kaplan-Meier analysis (88.8% vs 60.1%; log rank P = 0.001). Adjusting for age, gender and PVR, multivariate analysis identified peak VO₂ as a predictor of mortality [hazard ratio (HR): 2.78, 95% CI 1.01-7.63, P = 0.047]. In addition, peak VO₂ failed as an independent prognostic factor in a stepwise multivariate model including all variables significant in the univariate analysis.

In patients with inoperable CTEPH the peak VO₂ is a significant predictor of survival, when adjusting for age, gender and PVR. However, peak VO₂ failed as an independent prognostic factor when correcting for all significant baseline variables, which is limiting the clinical usability.