Early observations and pilot data that first suggested a new direction
SGLT2 inhibitors were developed as glucose-lowering agents for type 2 diabetes. In 2015, the EMPA-REG OUTCOME trial unexpectedly demonstrated that empagliflozin reduced cardiovascular death by 38% and heart failure hospitalisations by 35% in patients with type 2 diabetes and established cardiovascular disease. This signal was entirely unanticipated — the trial was designed to prove cardiovascular safety, not superiority. The magnitude of the heart failure benefit, appearing within weeks of randomisation, suggested a mechanism independent of glucose lowering.
Landmark RCTs and pivotal trials that established the evidence base
The cardiovascular signal demanded dedicated heart failure trials. DAPA-HF (2019) was the first to test dapagliflozin specifically in patients with heart failure with reduced ejection fraction (HFrEF), regardless of diabetes status. The result was unequivocal: a 26% reduction in the composite of worsening heart failure or cardiovascular death. EMPEROR-Reduced confirmed the class effect with empagliflozin, showing a 25% reduction in the same endpoint. Crucially, both trials demonstrated benefit in patients without diabetes, establishing that the heart failure effect was independent of glucose lowering.
Follow-up studies, subgroup analyses, and real-world validation
With HFrEF firmly established, the question turned to heart failure with preserved ejection fraction (HFpEF) — a condition with no previously proven therapy. EMPEROR-Preserved (2021) showed empagliflozin reduced the composite endpoint by 21% in HFpEF. DELIVER (2022) confirmed with dapagliflozin, demonstrating an 18% reduction. SOLOIST-WHF tested sotagliflozin in patients hospitalised for worsening heart failure, showing a 33% reduction in events. Together, these trials established SGLT2 inhibitors as the first drug class effective across the entire heart failure spectrum.
Integration into clinical practice guidelines and recommendations
The 2021 ESC Heart Failure Guidelines incorporated SGLT2 inhibitors as a Class I, Level A recommendation for HFrEF — the highest possible endorsement. The 2023 ESC Focused Update extended the Class I recommendation to all heart failure phenotypes regardless of ejection fraction. The AHA/ACC/HFSA 2022 guidelines similarly gave a Class 1 recommendation. SGLT2 inhibitors became the fourth pillar of foundational HFrEF therapy alongside ACEi/ARNi, beta-blockers, and mineralocorticoid receptor antagonists.
ESC 2021 Heart Failure Guidelines
Class I, Level A for SGLT2i in HFrEF
ESC 2023 Focused Update
Class I for SGLT2i in all HF regardless of EF
AHA/ACC/HFSA 2022 HF Guideline
Class 1 for SGLT2i in HFrEF and HFpEF
Now
Current standard of care and ongoing research directions
SGLT2 inhibitors are now considered foundational therapy for heart failure across the ejection fraction spectrum. They are one of the few drug classes to show consistent benefit in HFrEF, HFmrEF, and HFpEF. Current research focuses on optimal timing of initiation (including in-hospital starts during acute decompensation), combination with other novel agents, and understanding the precise mechanisms underlying their pleiotropic cardiovascular and renal benefits.
How did SGLT2 inhibitors go from diabetes drugs to heart failure treatment?+
The EMPA-REG OUTCOME trial in 2015 was designed to prove cardiovascular safety of empagliflozin in diabetes. It unexpectedly showed a 38% reduction in cardiovascular death and 35% reduction in heart failure hospitalisations. This led to dedicated heart failure trials (DAPA-HF, EMPEROR-Reduced) that confirmed the benefit even in patients without diabetes.
Do SGLT2 inhibitors work in heart failure with preserved ejection fraction?+
Yes. The EMPEROR-Preserved (2021) and DELIVER (2022) trials demonstrated that SGLT2 inhibitors reduce the composite of cardiovascular death or heart failure hospitalisation in HFpEF. This was groundbreaking because HFpEF had no previously proven pharmacotherapy.
What are the landmark trials for SGLT2 inhibitors in heart failure?+
The key trials are EMPA-REG OUTCOME (2015, the original signal), DAPA-HF (2019, first dedicated HFrEF trial), EMPEROR-Reduced (2020, confirmed class effect), EMPEROR-Preserved (2021, first HFpEF evidence), and DELIVER (2022, confirmed HFpEF benefit).
Are SGLT2 inhibitors now guideline-recommended for heart failure?+
Yes. The 2021 ESC guidelines gave a Class I, Level A recommendation for HFrEF. The 2023 ESC Focused Update extended this to all heart failure regardless of ejection fraction. The AHA/ACC 2022 guidelines similarly endorse SGLT2 inhibitors as foundational HF therapy.
