Is There a Benefit of Metformin after Heart Transplantation?

Abstract

Purpose Approximately 30% of patients undergoing heart transplantation (HTx) may have diabetes mellitus type 2 (DM2). More importantly, DM2 may become more prevalent after HTx because of high corticosteroid use. Metformin - an oral anti-hypoglycemic drug for DM2- has also been demonstrated to have immunomodulatory effects. It has been reported that metformin may decrease acute and chronic rejection as well as the development of cardiac allograft vasculopathy (CAV). Therefore, we reviewed our HTx patients placed on metformin pre-HTx and post-HTx to assess potential outcomes and benefits. Methods Between 2010 and 2017, we assessed 229 heart transplant patients with DM2. We divided these diabetic patients in those on metformin post-HTx (n=32) and those not on metformin (n=176). Metformin was continued for at least one-year post-transplant. Endpoints included 1-year survival, 1-year freedom from CAV (as defined by >30% stenosis via angiography), 1-year freedom from non-fatal major adverse cardiac events (NF-MACE: myocardial infarction, new congestive heart failure, percutaneous coronary intervention, implantable cardioverter defibrillator/pacemaker implant, stroke), and 1-year freedom from any-treated rejection (ATR), acute cellular rejection (ACR), and antibody-mediated rejection (AMR). Results There was no significant difference in 1-year survival in DM2 patients on metformin and DM2 patients not on metformin. There was no significant difference in 1-year freedom from CAV, NF-MACE or rejection between the groups (see table). Conclusion The use of metformin does not appear to demonstrate an immunomodulatory benefit. A larger cohort of patients are needed to confirm these findings.