Series: Landmark Trials in Endocrinology & Metabolism | Study #6
Category: SGLT2 Inhibitors · Heart Failure | Design: Multicentre, double-blind, placebo-controlled RCT | n: 3,730 | Follow-up: 16 months (median)
📋 Summary
Authors: Packer M et al., for the EMPEROR-Reduced Trial Investigators
Journal: N Engl J Med 2020;383:1413–1424 | DOI: 10.1056/NEJMoa2022190
EMPEROR-Reduced enrolled 3,730 patients with symptomatic heart failure and a left ventricular ejection fraction of 40% or less (NYHA class II, III, or IV), of whom 49.8% had type 2 diabetes. Patients were randomly assigned to empagliflozin 10 mg once daily or placebo on a background of optimised medical therapy. The primary composite outcome was cardiovascular death or hospitalisation for heart failure. Over a median follow-up of 16 months, the primary outcome occurred in 19.4% of patients in the empagliflozin group and 24.7% in the placebo group (HR 0.75; 95% CI 0.65 to 0.86; p<0.001), representing a 25% relative risk reduction. Hospitalisation for heart failure was substantially reduced (HR 0.69; 95% CI 0.59 to 0.81), while cardiovascular death was not individually statistically significant (HR 0.92; 95% CI 0.75 to 1.12). Empagliflozin also markedly attenuated the rate of decline in estimated glomerular filtration rate over the course of the trial (−0.55 vs −2.28 ml/min/1.73 m² per year), and a prespecified renal composite outcome including a sustained reduction in eGFR, end-stage kidney disease, or renal death was reduced by 50% (HR 0.50; 95% CI 0.32 to 0.77). The benefit was consistent across the subgroups with and without type 2 diabetes.
📊 Key Findings
| Outcome | Empagliflozin | Placebo | Effect Size |
|---|---|---|---|
| Primary composite (CV death or HF hospitalisation) | 19.4% | 24.7% | HR 0.75 (0.65–0.86) · p<0.001 · 25% RRR |
| HF hospitalisation | — | — | HR 0.69 (0.59–0.81) |
| Cardiovascular death | — | — | HR 0.92 (0.75–1.12) · NS |
| Renal composite (eGFR decline, ESKD, renal death) | — | — | HR 0.50 (0.32–0.77) · 50% RRR |
| eGFR slope | −0.55 ml/min/1.73m²/yr | −2.28 ml/min/1.73m²/yr | Difference +1.73 ml/min/1.73m²/yr |
| Benefit in T2DM subgroup | Consistent with overall | HR 0.72 (0.60–0.87) | |
| Benefit in non-T2DM subgroup | Consistent with overall | HR 0.78 (0.64–0.97) | |
| Absolute risk reduction (primary composite) | ~5.3% over 16 months | NNT approximately 19 | |
💬 Expert Commentary
EMPEROR-Reduced and DAPA-HF were conducted in parallel and reported within months of each other, and the two trials together constitute the evidence base for the universal inclusion of SGLT2 inhibitors in HFrEF management across all major cardiology guidelines. The numerical similarity of their primary outcomes, HR 0.75 in EMPEROR-Reduced versus HR 0.74 in DAPA-HF, is unlikely to be coincidental and reflects a consistent pharmacological effect shared across the SGLT2 inhibitor class in patients with systolic heart failure. EMPEROR-Reduced enrolled patients with a somewhat lower mean ejection fraction and a higher proportion of patients with more severe disease, including those with NYHA class III or IV symptoms and very low ejection fractions, and the benefit was maintained across this spectrum. The 50% reduction in the renal composite, the most dramatic cardiorenal finding reported in either HFrEF trial, is particularly notable. The rate of eGFR decline was more than four times faster in the placebo group than in the empagliflozin group, an observation that has significant implications for the long-term trajectory of renal function in patients with heart failure who are at high risk of concomitant CKD.
One important distinction from DAPA-HF lies in the cardiovascular death component. In DAPA-HF, cardiovascular death reached nominal significance at HR 0.82 (0.69–0.98); in EMPEROR-Reduced, it did not (HR 0.92; 0.75–1.12). The meta-analysis of both trials, conducted by the EMPEROR collaboration, found a consistent overall CV death reduction, suggesting that the individual trial results reflect statistical variability within trials of modest size rather than a true pharmacological difference between dapagliflozin and empagliflozin in this population. Both drugs are now standard of care in HFrEF regardless of diabetes status, and EMPEROR-Reduced provided critical confirmatory evidence that this class effect is robust and reproducible across manufacturers and trial designs.
Limitations: Cardiovascular death was not individually reduced at statistical significance. The median follow-up of 16 months limits assessment of long-term outcomes. Patients with severely impaired renal function (eGFR below 20 ml/min/1.73 m²) were excluded. The study was industry-sponsored by Boehringer Ingelheim and Eli Lilly.
🔑 BOTTOM LINE
EMPEROR-Reduced confirmed the findings of DAPA-HF, demonstrating that empagliflozin reduces cardiovascular death or heart failure hospitalisation by 25% in patients with HFrEF independent of diabetes status, and added the striking observation of a 50% reduction in a renal composite outcome, reinforcing the concurrent cardiorenal protection profile of SGLT2 inhibition in this population.
⭐ Clinical Impact Rating: ●●●●● Practice-defining
Next in the series: Study #7 DAPA-CKD: Dapagliflozin and Renal Outcomes in Chronic Kidney Disease
