Associations between kidney function and outcomes following cardiac rehabilitation in patients with heart failure

Abstract

Abstract Background Kidney dysfunction is considered one of the most prevalent comorbidities in patients with heart failure (HF). A combination of HF and kidney dysfunction is associated with peripheral muscle impairment, exercise intolerance, and poor prognosis. Conversely, cardiac rehabilitation (CR) for HF patients has been recognized to improve their clinical outcomes. However, the impact of kidney function on responses to CR in patients with HF is still unclear. Purpose This study aimed to investigate the associations between baseline kidney function and outcomes following CR including changes in physical function and prognosis in HF patients. Methods We reviewed a total of 3,727 patients who were admitted for HF treatment and underwent comprehensive CR during hospitalization. In addition to clinical characteristics, we assessed the kidney function using estimated glomerular filtration rate (eGFR) based on serum creatinine level at hospital discharge as baseline. The quadriceps strength (QS) and 6-minute walk distance (6MWD) were measured as muscle strength and functional capacity, respectively, at baseline. We also remeasured these parameter 5 months after hospital discharge in patients who participated in outpatient CR. The association between participation in outpatient CR and composite outcome of all-cause death and/or unplanned readmission were assessed using the multivariate Cox proportional hazard models in a subgroup of baseline eGFR. We also compared the changes in QS and 6MWD (ΔQS and Δ6MWD) between the eGFR stages. Results During the median follow-up period of 1.9 years, all-cause death/readmission occurred in 1604 (43.0%) patients, and their rate of incidence was 20.9/100 person-years. Out of studied patients, 1,585 (42.5%) patients participated in outpatient CR that was significantly associated with lower incidences of all-cause clinical events in patients with both eGFR ≥60 (adjusted hazard ratio [HR]: 0.73, 95% confidence interval [CI]: 0.60–0.89, P=0.002) and eGFR <60 (adjusted HR: 0.88, 95% CI: 0.78–0.99, P=0.045), but those with an eGFR <60 showed significant interaction between CR participation and adverse clinical events (interaction P<0.035, Figure 1). Among the outpatient CR participants, QS and 6MWD were significantly higher after 5-month CR than those at baseline (P<0.001, respectively), but the low baseline eGFR correlated with low ΔQS and Δ6MWD (trend P<0.001, respectively) even after adjustment for clinical confounding factors (Figure 2). Conclusions Although the outcomes following CR is affected by baseline kidney function, outpatient CR is significantly associated with the positive change in physical function and better prognosis in HF patients with low kidney function. Funding Acknowledgement Type of funding sources: None.