Exercise ventilation inefficiency and cardiovascular mortality in heart failure: the critical independent prognostic value of the arterial CO2 partial pressure.
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.
Guazzi
Marco
M
Cardiopulmonary Laboratory, Cardiology Division, University of Milano, San Paolo Hospital, Via A. di Rudinì, 8, 20142, Milano, Italy. marco.guazzi@unimi.it
Reina
Giuseppe
G
Tumminello
Gabriele
G
Guazzi
Maurizio D
MD
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
D002245:Carbon Dioxide