The featured report from the 6,000-patient EMPEROR-Preserved trial at the virtual annual congress of the European Society of Cardiology drew lots of attention for its headline finding: the first unequivocal demonstration that a medication, empagliflozin, can significantly reduce the rate of cardiovascular death and hospitalization for heart failure in patients with heart failure with preserved ejection fraction (HFpEF, a left ventricular ejection fraction of more than 40%), with the details simultaneously published online.
But at the same time, the EMPEROR-Preserved investigators released four additional reports with a lot more outcome analyses that also deserve some attention.
The puzzling neutral effect on renal events
Perhaps the most surprising and complicated set of findings among the main EMPEROR-Preserved outcomes involved renal outcomes.
The trial’s primary outcome was the combined rate of cardiovascular death or hospitalization for heart failure (HHF), and the results showed that treatment with empagliflozin (Jardiance) for a median of 26 months on top of standard treatment for patients with HFpEF led to a significant 21% relative risk reduction, compared with placebo-treated patients.
The trial had two prespecified secondary outcomes. One was the total number of HHF, which dropped by a significant 27%, compared with placebo. The second was the mean change in slope of estimated glomerular filtration rate (eGFR) on an annualized basis, and the empagliflozin regimen reduced the cumulative annual deficit, compared with placebo by an average of 1.36 mL/min per 1.73 m2, a significant difference.
This preservation of renal function was consistent with results from many prior studies of empagliflozin and all of the other U.S.-approved agents from the sodium-glucose cotransporter 2 inhibitor class. Preservation of renal function and a reduction in renal events has become a hallmark property of all agents in the SGLT2 inhibitor class both in patients with type 2 diabetes, as well as in those without diabetes but with heart failure with reduced ejection fraction (HFrEF) or with chronic kidney disease.
EMPEROR-Preserved threw a wrench into what had been an unbroken history of renal protection by SGLT2 inhibitors. That happened when a prespecified endpoint of the study – a composite renal outcome defined as time to first occurrence of chronic dialysis, renal transplantation, a sustained reduction of at least 40% in eGFR, or a sustained drop in eGFR of more than 10 or 15 mL/min per 1.73 m2 from baseline – yielded an unexpected neutral finding.
For this composite renal outcome, EMPEROR-Preserved showed a nonsignificant 5% reduction, compared with placebo, a result that both differed from what had been seen in essentially all the other SGLT2 inhibitor trials that had looked at this, but which also seemed at odds with the observed significant preservation of renal function that seemed substantial enough to produce a clinically meaningful benefit.
Renal effects blunted in HFpEF
The immediate upshot was a letter published by several EMPEROR-Preserved investigators that spelled out this discrepancy and came to the jolting conclusion that “eGFR slope analysis has limitations as a surrogate for predicting the effect of drugs on renal outcomes in patients with heart failure.”