title: Prognostic value of the oxygen uptake efficiency slope and other exercise variables in patients with coronary artery disease.
abstract: BACKGROUND
  Peak exercise capacity is an independent predictor for mortality in patients with coronary artery disease. However, sometimes cardiopulmonary exercise tests are stopped prematurely. Therefore, submaximal exercise measures such as the oxygen uptake efficiency slope have been introduced. The aim of this study was to assess the prognostic value of the oxygen uptake efficiency slope and other exercise parameters, in patients with coronary artery disease.
  
  
  METHODS
  Between 2000 and 2011, 1409 patients with coronary artery disease (age 60.7 ± 9.9 years; 1205 males) underwent cardiopulmonary exercise tests. A maximal effort was not reached in 161 (11.5%) patients. The oxygen uptake efficiency slope was calculated and information on mortality was obtained. Cox proportional hazards regression analyses were used to assess the relation of oxygen uptake efficiency slope and other gas exchange variables with all-cause and cardiovascular mortality. Receiver operating characteristic curve analyses was performed to define optimal cut-off values.
  
  
  RESULTS
  During an average follow-up of 7.45 ± 3.20 years (range 0.16-13.95 years), 158 patients died, among which 68 patients for cardiovascular reasons. The oxygen uptake efficiency slope was related to all-cause (hazard ratio: 0.568, p < 0.001) and cardiovascular (hazard ratio: 0.461, p < 0.001) mortality. When significant covariates were entered in the analysis, oxygen uptake efficiency slope remained related to mortality (p < 0.05). When other submaximal exercise parameters were added to the model, oxygen uptake efficiency slope and minute ventilation/carbon dioxide production slope also remained significantly related to mortality.
  
  
  CONCLUSIONS
  The oxygen uptake efficiency slope is an independent predictor for all-cause and cardiovascular mortality in patients with coronary artery disease, irrespective of a truly maximal effort during cardiopulmonary exercise tests. Furthermore, the oxygen uptake efficiency slope provides prognostic information, complementary to the minute ventilation/carbon dioxide production slope and peak exercise capacity.
authors: Department of Rehabilitation Sciences, KU Leuven and Department of Cardiovascular Diseases, University Hospitals of Leuven, Belgium.
authors: Ellen
authors: E
authors: Coeckelberghs
authors: Department of Rehabilitation Sciences, KU Leuven and Department of Cardiovascular Diseases, University Hospitals of Leuven, Belgium.
authors: Roselien
authors: R
authors: Buys
authors: Department of Rehabilitation Sciences, KU Leuven and Department of Cardiovascular Diseases, University Hospitals of Leuven, Belgium.
authors: Kaatje
authors: K
authors: Goetschalckx
authors: Department of Rehabilitation Sciences, KU Leuven and Department of Cardiovascular Diseases, University Hospitals of Leuven, Belgium.
authors: Véronique A
authors: VA
authors: Cornelissen
authors: Department of Rehabilitation Sciences, KU Leuven and Department of Cardiovascular Diseases, University Hospitals of Leuven, Belgium luc.vanhees@faber.kuleuven.be.
authors: Luc
authors: L
authors: Vanhees
mesh_terms: D000368:Aged; D019540:Area Under Curve; D002423:Cause of Death; D016009:Chi-Square Distribution; D003324:Coronary Artery Disease / Q000175:diagnosis* / Q000401:mortality / Q000503:physiopathology / Q000534:rehabilitation; D005080:Exercise Test; D017079:Exercise Tolerance; D005260:Female; D006801:Humans; D053208:Kaplan-Meier Estimate; D008297:Male; D008875:Middle Aged; D015999:Multivariate Analysis; D010101:Oxygen Consumption; D011237:Predictive Value of Tests; D011379:Prognosis; D016016:Proportional Hazards Models; D012372:ROC Curve; D018570:Risk Assessment; D012307:Risk Factors; D013997:Time Factors
keywords: Oxygen uptake efficiency slope; coronary artery disease; exercise capacity; prognosis