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 VO2) 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 VO2 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 in m(2). Patient characteristics and CPET parameters including Delta PETO2 (rest anaerobic threshold) were compared between the groups. The relationship between Delta PETO9 and peak VO2 was also investigated for each group. Results: In total, 201 patients were analyzed. Delta PETO2 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 (LVLF) and hemoglobin (Hb) were significantly associated with peak VO2 beta = 0.518,p < 0.001 and beta = 0.567, p < 0.001, respectively), whereas APETO(1) was not. In the eGFR 45-59 group, age, Hb, and APETO(2) showed a significant association with peak VO2 beta = -0.354, beta - 0.006; - 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 APETO(2) to peak VO2 (R-2 = 0.247, p < 0.001). Conclusions: The determinants of peak VO2 in heart disease patients depended on the stage of renal function. The determinants of peak VO2 in patients with eGFR <45 were INEF and Hb, while APET09 was the strongest predictor of peak VO2 in patients with eGFR 45-59.