Is ventilatory efficiency (VE/VCO 2 slope) associated with right ventricular oxidative metabolism in patients with congestive heart failure ?

Background: The relationship between minute ventilation and the rate of CO 2 elimination (VE/VCO 2 slope) is associated with mortality in patients with congestive heart failure (CHF). The VE/VCO 2 slope ≥ 34 denotes a poor prognosis and has been proposed to reflect abnormalities in pulmonary perfusion. Aims: To study whether increased VE/VCO 2 slope is associated with elevated right ventricular (RV) oxidative metabolism relative to the left ventricle (LV). Methods: 21 patients with stable NYHA II–III CHF underwent symptom limited cardiopulmonary exercise testing. Dynamic [ 11 C]acetate positron emission tomography (PET) was used to measure oxidative metabolism ( k mono ) of the LV and RV. Corrected RV oxidative metabolism (RVOx) was calculated as RV/LV k mono ratio. Results: Peak VO 2 was 16.2±4.1 ml/min/kg and the VE/VCO 2 slope was 33.4±6.1. LV and RV k mono were 0.046±0.009 and 0.037±0.007 min −1 , respectively, with a RVOx of 0.83±0.17. There was a good correlation between RVOx and the VE/VCO 2 slope ( r =0.61, p =0.0034). RVOx was 0.77±0.16 in patients with a VE/VCO 2 slope <34 and 0.93±0.16 in patients with VE/VCO 2 slope ≥34 ( p =0.047). Conclusion: RVOx correlates with VE/VCO 2 slope in CHF patients. This supports the hypothesis that pulmonary vascular resistance is a determinant of the VE/VCO 2 slope.