Renal Dysfunction in Heart Failure With Preserved Ejection Fraction: Insights From the RELAX Trial.

BACKGROUND: Patients with heart failure with preserved ejection fraction (HFpEF) and chronic kidney disease (CKD) represent a high-risk phenotype. The Phosphodiesterase-5 Inhibition to Improve Clinical Status and Exercise Capacity in Heart Failure with Preserved Ejection Fraction (RELAX) trial enrolled a high proportion of CKD participants, allowing investigation into differences in HFpEF by CKD status. METHODS AND
RESULTS: Among 212 participants, we investigated the associations of CKD with biomarkers, cardiac structure, and exercise capacity, and identified predictors of change in estimated glomerular filtration rate (eGFR) over trial follow-up. CKD participants (eGFR ≤60 mL/min/1.73m2) were older, had more comorbidities, and had worse diastolic function. Lower eGFR was associated with higher levels of endothelin-1, N-terminal pro-B-type natriuretic peptide, aldosterone, uric acid, and biomarkers of fibrosis (P < .05 for all). Whereas lower eGFR was associated with worse peak oxygen consumption (VO2) after adjustment for demographics, clinical comorbidities, exercise modality, ejection fraction, and chronotropic index (β coefficient per 1 SD decrease in eGFR: -0.61, 95% CI: -1.01, -0.22, P = .002), this association was attenuated after further adjustment for hemoglobin (β coefficient: -0.26, 95% CI: -0.68, 0.16, P = .22). Hemoglobin mediated 35% of the association between eGFR and peak VO2. Sildenafil therapy was independently associated with worsening eGFR over the trial (β coefficient: -2.79, 95% CI: -5.34, -0.24, P = .03).
CONCLUSION: Renal dysfunction in HFpEF is characterized by echocardiographic and biomarker profiles indicative of more advanced disease, and reduced hemoglobin is a strong mediator of the association between renal dysfunction and low exercise capacity. Sildenafil therapy was associated with worsening of renal function in RELAX.