VE/VCO₂ Slope in Older Heart Failure Patients With Normal Versus Reduced Ejection Fraction Compared With Age-Matched Healthy Controls

Background

Oxygen consumption (VO₂) has previously been used for prognosis and risk stratification in patients with heart failure. More recent research has introduced VE/VCO₂ slope as a prognostic measure. Risk of mortality is thought to increase when VE/VCO₂ slope values are greater than 34. Therefore, the purpose of this study was to cross-sectionally examine VE/VCO₂ slope in systolic heart failure (SHF) and diastolic heart failure (DHF) as well as age-matched healthy controls.

Methods and Results

Maximal graded exercise tests were conducted on 147 patients (59 DHF, 60 SHF, and 28 controls) using a bicycle ergometer. Breath-by-breath expired gas analysis was performed using a commercially available system with on-line computer calculations. VE/VCO₂ slope was calculated from a regression line of minute ventilation and carbon dioxide production. One-way analysis of covariance with a Benferroni post hoc test and Pearson correlations were used for statistical analysis. VE/VCO₂ slope was significantly higher in SHF when compared to both DHF (37 ± 8 vs. 34 ± 7, P = .03) and controls (37 ± 8 vs. 32 ± 5, P = .002). No significant difference was observed between DHF and healthy controls (34 ± 7 vs. 32 ± 5, P = .52). Additional analysis resulted in significant correlations between VO₂ and VE/VCO₂ slope in systolic heart failure patients (r = −0.40, P = .002); however, there was no significant relationships in diastolic heart failure patients (r = −0.09, P = .49) or in controls (r = 0.13, P = .50).

Conclusions

VE/VCO₂ slope is significantly higher in patients with SHF compared with DHF and healthy controls.

Key Words: Heart failure, VE/VCO₂ slope