Impact of metformin on the all-cause mortality of diabetic patients hospitalized with acute heart failure: An observational study using acute heart failure registry data

Background Although the hypothesis that metformin is beneficial for patients with diabetes and heart failure (HF) has been steadily raised, there is limited data on metformin use in patients with acute HF. We investigated the impact of metformin on all-cause mortality in hospitalized patients with type 2 diabetes and acute HF. Methods The Korean Acute Heart Failure registry enrolled patients hospitalized for acute HF from 2011 to 2014. Among this cohort, we analyzed patients with diabetes with baseline estimated glomerular filtration rate (eGFR) of 30 ml/min/1.73m 2 or more. We retrospectively investigated the all-cause mortality at 1 year after discharge. Inverse probability treatment weighting method was used to adjust baseline differences on metformin treatment. Results The study analyzed data from 1,309 patients with diabetes (mean age 69 years, 56% male). Among them, 613 (47%) patients were on metformin. During the median follow-up period of 11 months, 132 (19%) and 74 (12%) patients not receiving and receiving metformin treatment died, respectively. The all-cause mortality rate was lower in metformin users than in non-users (hazard ratio 0.616 [0.464–0.819], P < 0.001). HF readmission rate was not significantly different. After adjustment, metformin was significantly associated with a lower risk for all-cause mortality (hazard ratio 0.677 [0.495–0.928], P -value = 0.015). In subgroup analyses, this association remains significant irrespective of baseline kidney function (eGFR < 60 or ≥ 60 ml/min/1.73m 2 , P -for-interaction = 0.176) or left ventricular ejection fraction (< 40%, 40–49%, or ≥ 50%, P -for-interaction = 0.224). Conclusions Metformin treatment at the time of admission was associated with a lower risk for 1-year all-cause mortality in patients with diabetes, hospitalized for acute HF.