title: Maximal cardiac output determines 6 minutes walking distance in pulmonary hypertension.
abstract: OBJECTIVE
  The 6 minutes walk test (6MWT) is often shown to be the best predictor of mortality in pulmonary hypertension (PH) probably because it challenges the failing heart to deliver adequate cardiac output. We hypothesised that the 6MWT elicits maximal cardiac output as measured during a maximal cardiopulmonary exercise testing (CPET).
  
  
  METHODS
  18 patients with chronic thromboembolic pulmonary hypertension (n = 12) or pulmonary arterial hypertension (n = 6) and 10 healthy subjects performed a 6MWT and CPET with measurements of cardiac output (non invasive rebreathing device) before and directly after exercise. Heart rate was measured during 6MWT with a cardiofrequence meter.
  
  
  RESULTS
  Cardiac output and heart rate measured at the end of the 6MWT were linearly related to 6MW distance (mean±SD: 490±87 m). Patients with a high NT-pro-BNP achieve a maximum cardiac output during the 6MWT, while in normal subjects and in patients with a low-normal NT-proBNP, cardiac output at the end of a 6MWT was lower than achieved at maximum exercise during a CPET. In both cases, heart rate is the major determinant of exercise-induced increase in cardiac output. However, stroke volume increased during CPET in healthy subjects, not in PH patients.
  
  
  CONCLUSIONS
  Maximal cardiac output is elicited by 6MWT in PH patients with failing right ventricle. Cardiac output increase is dependent on chronotropic response in patients with PH.
authors.affiliation: Erasmus University Hospital, Department of Cardiology, Université Libre de Bruxelles, Brussels, Belgium.
authors.forename: Gaël
authors.initials: G
authors.lastname: Deboeck
authors.affiliation: Pulmonary Vascular Disease Unit, Papworth Hospital, Papworth, Cambridge, United Kingdom.
authors.forename: Dolores
authors.initials: D
authors.lastname: Taboada
authors.affiliation: Pulmonary Vascular Disease Unit, Papworth Hospital, Papworth, Cambridge, United Kingdom.
authors.forename: Guy
authors.initials: G
authors.lastname: Hagan
authors.affiliation: Pulmonary Vascular Disease Unit, Papworth Hospital, Papworth, Cambridge, United Kingdom.
authors.forename: Carmen
authors.initials: C
authors.lastname: Treacy
authors.affiliation: Pulmonary Vascular Disease Unit, Papworth Hospital, Papworth, Cambridge, United Kingdom.
authors.forename: Kathy
authors.initials: K
authors.lastname: Page
authors.affiliation: Pulmonary Vascular Disease Unit, Papworth Hospital, Papworth, Cambridge, United Kingdom.
authors.forename: Karen
authors.initials: K
authors.lastname: Sheares
authors.affiliation: Department of Physiology, Faculty of Medicine, Université Libre de Bruxelles, Brussels, Belgium.
authors.forename: Robert
authors.initials: R
authors.lastname: Naeije
authors.affiliation: Pulmonary Vascular Disease Unit, Papworth Hospital, Papworth, Cambridge, United Kingdom.
authors.forename: Joanna
authors.initials: J
authors.lastname: Pepke-Zaba
mesh_terms: D000328:Adult; D002302:Cardiac Output / Q000502:physiology*; D005080:Exercise Test / Q000379:methods*; D005260:Female; D006801:Humans; D006976:Hypertension, Pulmonary / Q000401:mortality / Q000503:physiopathology*; D008297:Male; D008875:Middle Aged; D016138:Walking