Commentary
ANAHEIM, CALIF. – When results from the EMPA-REG OUTCOME trial came out 2 years ago and showed a dramatic decrease in heart failure hospitalizations and deaths linked to treatment with the oral diabetes drug empagliflozin, some experts suggested that a completely hypothetical effect of empagliflozin on reducing fluid volume may have largely caused these unexpected clinical benefits.
New analyses of the trial results show this hypothesis may be at least partially correct.
Results from a post hoc analysis of data collected in Empagliflozin Cardiovascular Outcome Event Trial in Type 2 Diabetes Mellitus Patients (EMPA-REG OUTCOME) suggest that perhaps half the heart failure benefit was attributable to what appears to have been a roughly 7% drop in plasma volume in patients treated with empagliflozin (Jardiance), which began soon after treatment started and continued through the balance of the study, David Fitchett, MD, said at the American Heart Association scientific sessions.
Mitchel L. Zoler/Frontline Medical News
Dr. David Fitchett
“Markers of change in plasma volume were important mediators of the reduction in risk of hospitalization for heart failure or death from heart failure,” said Dr Fitchett, a cardiologist at St. Michael’s Hospital in Toronto and a coinvestigator of EMPA-REG OUTCOME (N Engl J Med. 2015 Nov 26;373[22]:2117-28).
The analysis also showed that a “modest” effect from a reduction in uric acid might explain about 20%-25% of the observed heart failure benefit, he reported. In contrast, none of the traditional cardiovascular disease risk factors examined in the analysis – including lipids, blood pressure, obesity, and hemoglobin A1c – appeared to have any relationship to the heart failure effects of empagliflozin.
Dr. Fitchett and his associates assessed the possible impact of a list of potential mediators with a statistical method that performed an unadjusted, univariate analysis of the time-dependent change in each of several variables relative to the observed changes in heart failure outcomes.
This analysis showed that on-treatment changes in two markers of plasma volume, hematocrit and hemoglobin, each showed changes that appeared to mediate about half of the heart failure effects. A third marker of plasma volume, albumin level, appeared to mediate about a quarter of the heart failure effects.
The changes in both hematocrit and hemoglobin first appeared within a few weeks of treatment onset, and soon reached a plateau that remained sustained through the balance of the study. For example, during the first 12 weeks of treatment, the average hematocrit level rose from about 41% at baseline to about 44%. This 3% net rise corresponds to about a 7% drop in plasma volume, Dr. Fitchett said.
In addition to reflecting a potentially beneficial decrease in fluid volume, this effect would also boost the oxygen-carrying capacity of a patient’s blood that could be beneficial for patients with ischemic heart disease and those with reduced left ventricular function, he noted.
The EMPA-REG OUTCOME trial was sponsored by Boehringer Ingelheim and Eli Lilly, which jointly market empagliflozin (Jardiance). Dr. Fitchett has received honoraria from those companies and also from Amgen, AstraZeneca, Merck, and Sanofi.
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