Left ventricular ejection fraction (LVEF) remains the principal parameter through which heart failure (HF) is classified, investigated, and treated. Yet, in heart failure with mildly reduced ejection fraction (HFmrEF), an LVEF between 41% and 49% provides only a partial characterization of the disease. HFmrEF encompasses diverse aetiologies, comorbidity profiles, and clinical trajectories [1]. More broadly, contemporary HF classification remains imperfect because of the biological complexity and dynamic nature of the syndrome [2].
