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

Abstract

Background: Identifying the causes of low peak oxygen uptake (peak V̇O2) 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 V̇O2 for each stage of renal function in heart disease patients, focusing on end-tidal oxygen partial pressure (PETO2). 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 ≥60 mL/min/1.73 m2. Patient characteristics and CPET parameters including ΔPETO2 (rest—anaerobic threshold) were compared between the groups. The relationship between ΔPETO2 and peak V̇O2 was also investigated for each group. Results: In total, 201 patients were analyzed. ΔPETO2 decreased with the deterioration of renal function (eGFR <45, 0.1 mmHg vs. eGFR 45–59, 2.4 mmHg vs. eGFR ≥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 V̇O2β = 0.518, p < 0.001 and β = 0.567, p < 0.001, respectively), whereas ΔPETO2 was not. In the eGFR 45–59 group, age, Hb, and ΔPETO2 showed a significant association with peak V̇O2 (β = –0.354, p = 0.006; β = 0.258, p = 0.007; β = 0.501, p < 0.001; respectively). In the univariate analysis, eGFR 45–59 group showed the highest coefficient of determination of ΔPETO2 to peak V̇O2 (R2 = 0.247, p < 0.001). Conclusions: The determinants of peak V̇O2 in heart disease patients depended on the stage of renal function. The determinants of peak V̇O2 in patients with eGFR <45 were LVEF and Hb, while ΔPETO2 was the strongest predictor of peak V̇O2 in patients with eGFR 45–59.

Keywords

• peak oxygen uptake
• heart disease
• renal dysfunction
• end-tidal oxygen partial pressure