Renal insufficiency leads to the exercise intolerance especially after anaerobic thresholds in heart failure patients

Abstract

Background and purpose: The maximal exercise capacity is generally reduced in heart failure (HF) patients. In addition, renal insufficiency was reported to be prevalent in patients with HF. However, the influence of renal dysfunction on exercise capacity, such as peak oxygen consumption (VO2), has not fully established. Therefore, the aim of this study was to investigate the relationship between cardiopulmonary exercise testing (CPX) parameters and renal function in HF patients. Methods: Four hundred and thirty patients with HF underwent echocardiography, laboratory measurements, and CPX. They were divided into two groups according to estimated glomerular filtration rate (eGFR) <60 [mL/min/1.73m2] (n=141) or eGFR ≥60 (n=289). Each patient performed a progressively increasing work rate CPX to maximum tolerance on a cycle ergometer, and respiratory gas exchange variables were acquired continuously throughout exercise, breath by breath. (VO2(peak)-VO2(AT))/VO2(peak) and (VO2(RC)-VO2(AT))/VO2(RC) were calculated as exercise capacity after anaerobic thresholds (AT) [RC: respiratory compensation point]. Results: One hundred and eighty nine ischemic cardiomyopathy, 132 dilated cardiomyopathy and 59 hypertrophic cardiomyopathy patients were included in this study. The average of left ventricular ejection fraction (LVEF), eGFR, hemoglobin level, and peak VO2 were 50.1 [%], 68.6 [mL/min/1.73m2], 13.6 [g/dL], and 19.4 [mL/kg/min]. In the eGFR<60 group, peak VO2 was lower than in the eGFR≥60 group (17.5 vs 20.3, p<0.001). (VO2(peak)-VO2(AT))/VO2(peak) was significantly lower in the eGFR<60 group (0.30 vs 0.35, p<0.001). Furthermore, (VO2(RC)-VO2(AT))/VO2(RC) was significantly lower in the eGFR<60 group (0.22 vs 0.25, p=0.002). Multivariate analysis revealed that eGFR(p=0.04), hemoglobin level (p=0.04), LVEF (p=0.004), and age (p<0.001) were significant determinants of (VO2(peak)-VO2(AT))/VO2(peak). As to (VO2(RC)-VO2(AT))/VO2(RC), hemoglobin level was a significant determinant (p=0.048), but eGFR was not (p=0.09). Conclusions: Renal dysfunction might be associated with reduced exercise capacity in HF patients. The exercise intolerance after AT may contribute to impaired overall exercise capacity and hemoglobin level may be an important factor for respiratory compensation after AT in HF patients with renal insufficiency.