The influence of metformin and the presence of type 2 diabetes mellitus on mortality and hospitalisation in patients with heart failure

Background: Metformin is one of the antihyperglycaemic drugs, reducing the risk of major cardiovascular events, including fatal ones. Although it is formally contraindicated in moderate and severe functional stages of heart failure (HF), it is commonly used in patients with concomitant type 2 diabetes mellitus (T2DM).Aim: We sought to evaluate the effect of metformin and T2DM on total mortality and hospitalisation rates in patients with HF.Methods: This retrospective analysis included 1030 adult patients (> 18 years) with HF from the Polish section of the HF Long-Term Registry (enrolled between 2011 and 2014). Patients with T2DM (n = 350) were identified and divided into two groups: those receiving metformin and those not. Both groups were subjected to one-year follow-up.Results: Mean patient age was 65.3 ± 13.5 years, with the predominance of male sex (n = 726) and obesity (mean bodymass index 30.3 ± 5.5 kg/m2) and mean left ventricular ejection fraction was 34.3% ± 14.1%. Among patients with T2DM (n = 350) only 135 (38.6%) were treated with metformin. During one-year follow-up, 128 patients with HF died, of whom 53 had T2DM (15.1% vs. 10.9%, hazard ratio [HR] 0.89, 95% confidence interval [CI] 0.87–0.91, p = 0.045). Metformin was associated with a lower mortality rate compared to other antihyperglycaemic agents (9.6% vs. 18.6%, HR 0.85; 95% CI 0.81–0.89, p = 0.023). There were no significant differences in the hospitalisation rate, including that due to HF decompensation, among patients treated with metformin and the remainder (53.5% vs. 40.0%, respectively HR 0.93, 95% CI 0.82–1.04, p = 0.433).Conclusions: Metformin treatment in patients with different degrees of HF and T2DM is associated with a reduction in mortality and does not affect the hospitalisation rate