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Is ventilatory efficiency (VE/VCO(2) slope) associated with right ventricular oxidative metabolism in patients with
Heikki Ukkonen1, Ian G Burwash, William Dafoe
1Department of Medicine, Turku University Hospital, Turku, Finland. heikki.ukkonen@tyks.fi
Background:
The relationship between minute ventilation and the rate of CO2 elimination (VE/VCO2 slope) is associated with mortality in patients with congestive heart failure (CHF). The VE/VCO2 slope > or =34 denotes a poor prognosis and has been proposed to reflect abnormalities in pulmonary perfusion.
Aims:
To study whether increased VE/VCO2 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 VO2 was 16.2+/-4.1 ml/min/kg and the VE/VCO2 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/VCO2 slope (r=0.61, p=0.0034). RVOx was 0.77+/-0.16 in patients with a VE/VCO2 slope <34 and 0.93+/-0.16 in patients with VE/VCO2 slope > or =34 (p=0.047).
Conclusion:
RVOx correlates with VE/VCO2 slope in CHF patients. This supports the hypothesis that pulmonary vascular resistance is a determinant of the VE/VCO2 slope.
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