Limited predictive value of cardiopulmonary exercise indices in patients with moderate chronic heart failure treated with carvedilol

Abstract 

Background

Peak oxygen consumption (VO2) is traditionally used for risk stratification in chronic heart failure (CHF); however, its predictive value is unknown with carvedilol treatment. Therefore, we sought to investigate the prognostic role of gas-exchange parameters obtained from symptom-limited cardiopulmonary exercise testing (CPX) in patients with CHF that is treated with carvedilol.

Methods

A total of 508 consecutive patients (443 men, mean age [± SD] 59 ± 9 years) with a mean left ventricular ejection fraction (LVEF) of 25% ± 7% underwent CPX. The peak VO2 was 13.9 ± 3 mL/kg/min; the rate of increase of minute ventilation per unit of increase of carbon dioxide production (VE/VCO2 slope) was 32 ± 2. Outcomes (cardiovascular death or urgent heart transplantation) were determined when all patients who survived had been observed for a minimum of 6 months.

Results

Patients were divided into groups according to treatment (carvedilol and non-carvedilol); 236 patients were treated with carvedilol (46%), at a mean dose of 25 ±13 mg. The VE/CO2 slope, LVEF, peak VO2, and carvedilol treatment were revealed by means of multivariate analysis to be independent and additional predictors in the total population; VE/VCO2 slope, LVEF, and peak VO2 were revealed to be independent and additional predictors in the patients in the noncarvedilol group (all P <.001); and only peak VO2 was revealed to be an independent and additional predictor in the patients in the carvedilol group (P <.01). In the carvedilol group, mortality rates were 26%, 11%, 10%, and 4% (P <.05) in patients with peak VO2 ≤10 mL/kg/min, >10 to ≤14 mL/kg/min, >14 to18 mL/kg/min, and ≥18 mL/kg/min, respectively. No difference in mortality rates according to peak VO2 or additional outcome indices were identified in the 212 patients with peak VO2 >10 mL/kg/min.

Conclusions

Peak VO2 provides limited predictive information in patients with CHF that is treated with carvedilol, and no additional gas exchange parameter yields supplementary advice.