title: The lowest VE/VCO₂ ratio best identifies chronic thromboembolic pulmonary hypertension.
abstract: BACKGROUND
  The natural history of acute pulmonary embolism (PE) under treatment is about a gradual resolution of the thrombi, and uncommonly, the development of chronic thromboembolic pulmonary hypertension (CTEPH). We hypothesized that ventilatory efficiency parameters during cardiopulmonary exercise testing (CPET) may be able to monitor the process and predict CTEPH.
  
  
  METHODS
  15 patients rehabilitated from acute PE (total resolution of thrombi), 44 patients with chronic PE (with residual thrombi), 66 patients with CTEPH, and 36 sedentary healthy controls performed incremental CPET.
  
  
  RESULTS
  The lowest VE/VCO₂ was higher in CTEPH patients than that in chronic PE and rehabilitated patients (43.4 L/min vs 29.9 L/min vs 27.1 L/min, p<0.005). The VE/VCO₂ slope (48.4 L/min/L/min vs 29.9 L/min/L/min vs 28.0 L/min/L/min, p<0.005) and oxygen uptake efficiency plateau (OUEP) (37.1 L/min vs 27.0 L/min vs 25.2L/min, p<0.005) had the similar changes. In logistic regression analysis, the lowest VE/VCO₂ ≥ 34.35 L/min was the best predictor of CTEPH (OR 159.0, 95% CI 36.0-702.3, p<0.001). The lowest VE/VCO₂ was higher in chronic PE patients compared with the controls (29.9 L/min vs 26.5 L/min, p<0.05), but there was no difference between the rehabilitated patients and the controls. In multiple linear regression analysis, the percentage of vascular obstruction by ventilation-perfusion lung scanning (PVO) was the most significant independent predictor for indices of ventilatory efficiency in chronic PE and rehabilitated patients.
  
  
  CONCLUSIONS
  CTEPH is associated with weakened ventilatory efficiency. The lowest VE/VCO₂ ratio has the best capability to predict CTEPH. Ventilatory inefficiency improves along with recovery of acute PE.
authors.affiliation: State Key Laboratory of Cardiovascular Disease, Fuwai Hospital, National Center for Cardiovascular Diseases, Chinese Academy of Medical Sciences and Peking Union Medical College, China; Center for Pulmonary Vascular Diseases, State Key Laboratory of Cardiovascular Disease, Fuwai Hospital, National Center for Cardiovascular Diseases, Chinese Academy of Medical Sciences and Peking Union Medical College.
authors.forename: Qunying
authors.initials: Q
authors.lastname: Xi
authors.affiliation: Center for Pulmonary Vascular Diseases, State Key Laboratory of Cardiovascular Disease, Fuwai Hospital, National Center for Cardiovascular Diseases, Chinese Academy of Medical Sciences and Peking Union Medical College.
authors.forename: Zhihui
authors.initials: Z
authors.lastname: Zhao
authors.affiliation: Center for Pulmonary Vascular Diseases, State Key Laboratory of Cardiovascular Disease, Fuwai Hospital, National Center for Cardiovascular Diseases, Chinese Academy of Medical Sciences and Peking Union Medical College. Electronic address: fuwaipumc@163.com.
authors.forename: Zhihong
authors.initials: Z
authors.lastname: Liu
authors.affiliation: Center for Pulmonary Vascular Diseases, State Key Laboratory of Cardiovascular Disease, Fuwai Hospital, National Center for Cardiovascular Diseases, Chinese Academy of Medical Sciences and Peking Union Medical College.
authors.forename: Xiuping
authors.initials: X
authors.lastname: Ma
authors.affiliation: Center for Pulmonary Vascular Diseases, State Key Laboratory of Cardiovascular Disease, Fuwai Hospital, National Center for Cardiovascular Diseases, Chinese Academy of Medical Sciences and Peking Union Medical College.
authors.forename: Qin
authors.initials: Q
authors.lastname: Luo
authors.affiliation: State Key Laboratory of Cardiovascular Disease, Fuwai Hospital, National Center for Cardiovascular Diseases, Chinese Academy of Medical Sciences and Peking Union Medical College, China; Center for Pulmonary Vascular Diseases, State Key Laboratory of Cardiovascular Disease, Fuwai Hospital, National Center for Cardiovascular Diseases, Chinese Academy of Medical Sciences and Peking Union Medical College.
authors.forename: Weihua
authors.initials: W
authors.lastname: Liu
mesh_terms: D002908:Chronic Disease; D005080:Exercise Test / Q000379:methods*; D005260:Female; D006801:Humans; D006976:Hypertension, Pulmonary / Q000175:diagnosis* / Q000209:etiology* / Q000534:rehabilitation; D008297:Male; D008875:Middle Aged; D011655:Pulmonary Embolism / Q000150:complications* / Q000175:diagnosis* / Q000534:rehabilitation; D011659:Pulmonary Gas Exchange; D015203:Reproducibility of Results; D012680:Sensitivity and Specificity; D016896:Treatment Outcome
keywords: Cardiopulmonary exercise testing; Chronic thromboembolic pulmonary hypertension; Pulmonary embolism