FINE-FUNCTION HF: FINErenone and FUNCTIONal capacity in heart failure after switching from spironolactone to finerenone

Background While finerenone has demonstrated cardiovascular benefit in HFpEF and HFmrEF, its early effects on objective functional capacity have been poorly characterized. In particular, short-term changes in functional performance and patient-reported health status following therapeutic optimization remain underreported, despite their relevance for patient-centered care and therapeutic decision-making. Methods This prospective, single-centre study included consecutive patients with HFpEF/HFmrEF who underwent a therapeutic switch from spironolactone to finerenone as part of routine clinical care. Functional capacity was evaluated using the 6-minute walk test (6MWT), while health status was assessed with the Kansas City Cardiomyopathy Questionnaire (KCCQ), including total and domain-specific scores. All assessments were performed at baseline and repeated after 30 days. Safety was evaluated through changes in renal function and serum potassium levels. Paired comparisons were conducted using appropriate parametric or non-parametric tests, effect sizes were calculated, and correlations between changes in functional capacity and patient-reported outcomes were explored. The study was approved by the local ethics committee in accordance with the Declaration of Helsinki and all participants provided written informed consent. Results Fifty-three patients were included (mean age 71.8 ± 1.3 years; 45.3% male; mean LVEF 57.8 ± 1.3%). At 30 days, a clinically meaningful improvement in functional capacity was observed, with 6MWT distance increasing from 263.6 ± 12.9 m to 302.0 ± 11.4 m (Δ +38.4 m; 95% CI 15.9–41.4; p<0.001; Cohen’s d = 0.64). This magnitude of improvement exceeds commonly accepted thresholds for clinical relevance in functional capacity. KCCQ total score improved from 48.5 ± 3.5 to 67.1 ± 3.5 (Δ +18.7; p<0.001), with consistent gains across overall score, physical limitation, and symptom domains (all p<0.001; large effect sizes). Changes in 6MWT and KCCQ were not correlated, indicating that objective functional performance and patient-reported health status captured distinct and complementary aspects of treatment response, while lower baseline KCCQ scores were associated with greater clinical improvement (ρ = −0.437; p = 0.002). No significant changes were observed in creatinine, microalbuminuria, urea, or potassium levels. No cases of clinically relevant hyperkalaemia or treatment discontinuation due to adverse events were observed. Conclusions In patients with HFpEF/HFmrEF, finerenone initiation was associated with early, clinically meaningful improvements in objective functional capacity and patient-reported health status within 30 days, without compromising short-term safety. These findings support the concept that mineralocorticoid receptor modulation may confer measurable early functional benefit, expanding its clinical relevance beyond long-term outcome modification in HFpEF/HFmrEF.Picture 1Picture 2