Cardiopulmonary exercise testing for prognosis in chronic heart failure: continuous and independent prognostic value from VE/VCO2slope and peak VO2

Abstract

Background Chronic heart failure carries a poor prognosis. Cardiopulmonary exercise testing is useful in predicting survival. We set out to establish the prognostic value of peak VO₂and VE/VCO₂slope across a range of threshold values. Method and Results Three hundred and three consecutive patients with stable chronic heart failure underwent cardiopulmonary exercise testing between 1992 and 1996. Their age was 59±11 years (mean±SD), peak VO₂17·8± 6·6ml.kg⁻¹min⁻¹, VE/VCO₂slope 37±12. At the end of follow-up in January 1999, 91 patients had died (after a median of 7 months, interquartile range 3–16 months). The median follow-up for the survivors was 47 months (interquartile range 37–57 months). The areas under the receiver-operating characteristic curves for predicting mortality at 2 years were 0·77 for both peak VO₂and VE/VCO₂slope. With peak VO₂and VE/VCO₂slope viewed as continuous variables in the Cox proportional-hazards model, they were both highly significant prognostic indicators, both in univariate analysis and bivariate analysis (P2slope, P2). Conclusions Lower peak VO₂implies poorer prognosis across a range of values from 10 to 20ml.kg⁻¹min⁻¹, without a unique threshold. Gradations of elevation of the VE/VCO₂slope also carry prognostic information over a wide range (30–55). The two parameters are comparable in terms of prognostic power, and contribute complementary prognostic information.