title: Exercise ventilation inefficiency and cardiovascular mortality in heart failure: the critical independent prognostic value of the arterial CO2 partial pressure.
abstract: OBJECTIVE
  In chronic heart failure (CHF) patients, the ventilation (Ve) needed to eliminate metabolically produced CO(2) during exercise (i.e. the Ve/Vco(2) slope) is a strong prognosticator. Ve/Vco(2) slope determinants are the dead space-tidal volume (Vd/Vt) ratio and the arterial CO(2) partial pressure (Paco(2)). We aimed at defining the respective prognostic role of these two variables.
  
  
  RESULTS
  One hundred and twenty-eight stable CHF patients (average left ventricular ejection fraction 34+/-10%) underwent cardiopulmonary exercise testing and blood gas analysis. The prognostic relevance of the Ve/Vco(2) slope, Vd/Vt, and Paco(2) at peak exercise was evaluated by the Kaplan-Meier approach with log-rank testing and by multivariate Cox regression analysis. During a mean period of 31.3+/-20 months, 24 patients died from cardiac causes. In univariate analysis, predictors of death included the use of anti-aldosterone drugs, low peak Vo(2), peak Ve/Vo(2), peak Paco(2) and high Ve/Vco(2) slope, and peak Vd/Vt. Multivariate analysis identified a low peak Paco(2) (<35 mmHg) as the strongest independent prognostic indicator [hazard ratio 4.65, 95% confidence interval (CI) (1.695-12.751), P=0.003] that primarily accounts for the Ve/Vco(2) slope prognostic power.
  
  
  CONCLUSIONS
  These findings imply that regulatory mechanisms involved in the tight control of ventilatory command and blood gas tension, rather than lung function abnormalities, play a critical pathophysiological role in the exercise ventilation inefficiency of CHF patients.
authors.affiliation: Cardiopulmonary Laboratory, Cardiology Division, University of Milano, San Paolo Hospital, Via A. di Rudinì, 8, 20142, Milano, Italy. marco.guazzi@unimi.it
authors.forename: Marco
authors.initials: M
authors.lastname: Guazzi
authors.forename: Giuseppe
authors.initials: G
authors.lastname: Reina
authors.forename: Gabriele
authors.initials: G
authors.lastname: Tumminello
authors.forename: Maurizio D
authors.initials: MD
authors.lastname: Guazzi
mesh_terms: D001784:Blood Gas Analysis; D002245:Carbon Dioxide / Q000097:blood*; D004452:Echocardiography; D015444:Exercise / Q000502:physiology*; D005080:Exercise Test / Q000379:methods; D005260:Female; D005541:Forced Expiratory Volume / Q000502:physiology; D006333:Heart Failure / Q000097:blood / Q000401:mortality / Q000503:physiopathology*; D006801:Humans; D008297:Male; D008875:Middle Aged; D015999:Multivariate Analysis; D010101:Oxygen Consumption / Q000502:physiology; D010313:Partial Pressure; D011379:Prognosis; D012126:Respiratory Dead Space / Q000502:physiology*; D012131:Respiratory Insufficiency / Q000097:blood / Q000401:mortality / Q000503:physiopathology*; D016019:Survival Analysis; D014797:Vital Capacity / Q000502:physiology
chemical_list: D002245:Carbon Dioxide