Landmark clinical trials shaping contemporary guideline-directed medical therapy for heart failure.

Heart failure (HF) management has evolved substantially over recent decades, transitioning from predominantly symptomatic treatment to a strategy grounded in disease-modifying therapies that improve survival and reduce hospitalizations. This review provides a structured and clinically oriented synthesis of landmark randomized controlled trials (RCTs) that have shaped contemporary guideline-directed medical therapy across the spectrum of left ventricular ejection fraction (LVEF). Evidence from pivotal large-scale RCTs is presented according to pharmacological classes, encompassing both foundational and selected adjunctive therapies. In HF with reduced LVEF, multiple drug classes consistently reduce mortality and HF hospitalizations, forming the basis of contemporary quadruple therapy. In contrast, evidence in HF with mildly reduced or preserved LVEF remains more heterogeneous, with sodium-glucose co-transporter-2 inhibitors emerging as the only class with consistent benefit across the full LVEF spectrum. Additional therapies, including digoxin, vericiguat, intravenous iron, and emerging incretin-based agents, provide incremental benefits in selected clinical contexts. Differences in trial populations, design, and background therapy limit direct comparisons but highlight the progressive refinement of HF treatment strategies. Despite the strength of the evidence base, a persistent gap remains between guideline recommendations and real-world implementation. Bridging this gap, improving representation of under-represented populations in clinical trials, and advancing precision medicine approaches remain key priorities for future research.