Determinants of Peak Oxygen Uptake at Each Stage of Renal Dysfunction in Patients with Heart Disease

Background: Identifying the causes of low peak oxygen uptake (peak V̇O ${}_{2}$ ) in heart disease patients with renal dysfunction is necessary for prognostic improvement strategies. The purpose of this study was to verify the determinants of peak V̇O ${}_{2}$ for each stage of renal function in heart disease patients, focusing on end-tidal oxygen partial pressure (PETO ${}_{2}$ ). Methods: Two hundred fifty heart disease patients who underwent cardiopulmonary exercise testing (CPET) in our institution were consecutively enrolled. Patients were divided into three groups by their estimated glomerular filtration rate (eGFR): $<$ 45, 45–59 and $\geq$ 60 mL/min/1.73 m ${}^{2}$ . Patient characteristics and CPET parameters including $\Delta{}$ PETO ${}_{2}$ (rest—anaerobic threshold) were compared between the groups. The relationship between $\Delta{}$ PETO ${}_{2}$ and peak V̇O ${}_{2}$ was also investigated for each group. Results: In total, 201 patients were analyzed. $\Delta{}$ PETO ${}_{2}$ decreased with the deterioration of renal function (eGFR $<$ 45, 0.1 mmHg vs. eGFR 45–59, 2.4 mmHg vs. eGFR $\geq$ 60, 5.2 mmHg, p $<$ 0.001). In the eGFR $<$ 45 group, left ventricular ejection fraction (LVEF) and hemoglobin (Hb) were significantly associated with peak V̇O ${}_{2}$ $\beta{}$ = 0.518, p $<$ 0.001 and $\beta{}$ = 0.567, p $<$ 0.001, respectively), whereas $\Delta{}$ PETO ${}_{2}$ was not. In the eGFR 45–59 group, age, Hb, and $\Delta{}$ PETO ${}_{2}$ showed a significant association with peak V̇O ${}_{2}$ ( $\beta{}$ = –0.354, p = 0.006; $\beta{}$ = 0.258, p = 0.007; $\beta{}$ = 0.501, p $<$ 0.001; respectively). In the univariate analysis, eGFR 45–59 group showed the highest coefficient of determination of $\Delta{}$ PETO ${}_{2}$ to peak V̇O ${}_{2}$ (R ${}^{2}$ = 0.247, p $<$ 0.001). Conclusions: The determinants of peak V̇O ${}_{2}$ in heart disease patients depended on the stage of renal function. The determinants of peak V̇O ${}_{2}$ in patients with eGFR $<$ 45 were LVEF and Hb, while $\Delta{}$ PETO ${}_{2}$ was the strongest predictor of peak V̇O ${}_{2}$ in patients with eGFR 45–59.

Keywords

peak oxygen uptake

heart disease

renal dysfunction

end-tidal oxygen partial pressure

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Fig. 1.

Comparison of the change in end-tidal oxygen partial pressure ( $\Delta{}$ PETO ${}_{2}$ ) at different values of estimated glomerular filtration rate (eGFR).

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Rev. Cardiovasc. Med. Print ISSN 1530-6550 Electronic ISSN 2153-8174