title: Associations of cardiovascular and all-cause mortality events with oxygen uptake at ventilatory threshold.
abstract: BACKGROUND
  Oxygen uptake (VO2) at ventilatory threshold (VT), is a cardiopulmonary exercise testing parameter which may be a proxy for peak VO2. We aimed to assess the associations of VO2at VT with sudden cardiac death (SCD), fatal coronary heart disease (CHD) and cardiovascular disease (CVD), and all-cause mortality.
  
  
  RESULTS
  VO2at VT was assessed during a submaximal exercise test using respiratory gas analyzers in the Kuopio Ischemic Heart Disease cohort of 1639 middle-aged men. Hazard ratios (HRs) (95% CIs) were assessed. During a median follow-up of 25.6years, 121 SCDs, 202 fatal CHDs, 312 fatal CVDs, and 703 all-cause mortality events occurred. VO2at VT was correlated with peak VO2(r=0.90) and linearly associated with each outcome. Comparing extreme quartiles of VO2at VT, the HRs (95% CIs) for SCD, fatal CHD, fatal CVD, and all-cause mortality on adjustment for established risk factors were 0.37 (0.18-0.78), 0.32 (0.18-0.57), 0.45 (0.30-0.69), and 0.50 (0.38-0.64) respectively. The HRs were 1.02 (0.36-2.91), 1.43 (0.63-3.25), 1.46 (0.79-2.71), and 1.02 (0.69-1.51) respectively on further adjustment for peak VO2. Addition of VO2at VT to a CVD mortality risk prediction model containing established risk factors significantly improved risk discrimination and reclassification at 25years.
  
  
  CONCLUSIONS
  There are linear and inverse associations of VO2 at VT with fatal cardiovascular and all-cause mortality events, which are dependent on peak VO2. Inclusion of VO2at VT in the standard established risk factors panel significantly improves the prediction and classification of long-term CVD mortality risk.
authors.affiliation: School of Clinical Sciences, University of Bristol, Learning & Research Building (Level 1), Southmead Hospital, Southmead Road, Bristol, UK. Electronic address: skk31@cantab.net.
authors.forename: Setor K
authors.initials: SK
authors.lastname: Kunutsor
authors.affiliation: Institute of Public Health and Clinical Nutrition, University of Eastern Finland, Kuopio, Finland. Electronic address: sudhir.kurl@uef.fi.
authors.forename: Sudhir
authors.initials: S
authors.lastname: Kurl
authors.affiliation: Emory University School of Medicine, Atlanta, GA, USA. Electronic address: drhasankhan@gmail.com.
authors.forename: Hassan
authors.initials: H
authors.lastname: Khan
authors.affiliation: Diabetes Research Centre, University of Leicester, Leicester, UK. Electronic address: frazac@fastwebnet.it.
authors.forename: Francesco
authors.initials: F
authors.lastname: Zaccardi
authors.affiliation: Institute of Public Health and Clinical Nutrition, University of Eastern Finland, Kuopio, Finland; Central Finland Central Hospital, Internal Medicine, Jyväskylä, Finland. Electronic address: jariantero.laukkanen@uef.fi.
authors.forename: Jari A
authors.initials: JA
authors.lastname: Laukkanen
mesh_terms: D000328:Adult; D015308:Anaerobic Threshold / Q000502:physiology*; D002318:Cardiovascular Diseases / Q000175:diagnosis / Q000401:mortality* / Q000503:physiopathology; D016757:Death, Sudden, Cardiac / Q000453:epidemiology*; D005080:Exercise Test / Q000401:mortality* / Q000639:trends; D005387:Finland / Q000453:epidemiology; D006801:Humans; D008297:Male; D008875:Middle Aged; D010101:Oxygen Consumption / Q000502:physiology*; D011446:Prospective Studies; D012123:Pulmonary Ventilation / Q000502:physiology*
keywords: All-cause mortality; Cardiopulmonary exercise testing; Fatal cardiovascular disease; Oxygen uptake at ventilatory threshold; Peak oxygen uptake; Risk prediction