BACKGROUND : Cardiopulmonary exercise testing (CPET) is the gold standard for the integrated assessment of cardiovascular, respiratory, and metabolic responses during exercise. In patients with heart failure (HF), peak oxygen uptake (pVO₂) and the VE/VCO₂ slope are well-established prognostic markers. Beyond these, dynamic parameters such as the variation of heart rate (ΔHR) and the increase in stroke volume (ΔSV) that reflect chronotropic and contractile reserve, respectively, may be more sensitive than left ventricular ejection fraction (LVEF) in predicting functional capacity and outcomes. METHODS : We prospectively analyzed 174 HF patients who underwent CPET with non-invasive cardiac output monitoring (Physioflow) and rest echocardiography between Nov 2024 and Feb 2025 at Centro Cardiologico Monzino, Milan. Continuous variables are expressed as mean ± standard deviation. Correlations between parameters assessed using Pearson’s coefficient; ΔSV and ΔHR were stratified into tertiles and compared using one-way ANOVA. RESULTS : A total of 174 patients were analyzed (mean age 66 years, LVEF 40%). During exercise, both HR and SV increased, with a mean Δ of 46 bpm and 25 ml, respectively. ΔHR showed a strong correlation with pVO₂ (r = 0.53) as well as ΔSV (r = 0.38). Differently, LVEF showed only modest associations with pVO 2 (r= 0.22). pVO₂ correlated strongly with oxygen pulse (r = 0.78) and inversely with VE/VCO₂ slope (r = –0.56). Tertile analysis identified functional cut-offs for ΔHR (≤35, 35–56, >56 bpm) and ΔSV (≤20, 20–29, >29 ml), which stratified aerobic capacity (p < 0.001). CONCLUSION : Exercise performance in HF patients depends primarily on the dynamic increase in HR and SV, rather than resting LVEF. ΔHR and ΔSV emerge as key predictors of aerobic capacity and potential prognostic markers. CPET remains an indispensable tool for functional evaluation and risk stratification, providing insights not accessible through echocardiography alone.
Associazione Nazionale Medici Cardiologi Ospedalieri
