A Review of Cardiovascular Outcomes Trials of Glucose-Lowering Therapies and Their Effects on Heart Failure Outcomes.

Type 2 diabetes mellitus has long been recognized as a major risk factor for adverse atherosclerotic cardiovascular disease events; however, recent data indicate that heart failure is now emerging as the most common and morbid cardiovascular complication of type 2 diabetes mellitus. When heart failure develops in patients with type 2 diabetes, prognosis is ominous, highlighting the need for glucose-lowering therapies that can prevent heart failure, improve outcomes, or both. Prior to 2008, there was a paucity of randomized controlled trials evaluating long-term cardiovascular outcomes with glucose-lowering therapies. This changed after guidance on the assessment of novel glucose-lowering agents was issued by both the US Food and Drug Administration and the European Medicines Agency. Since then, significant progress has been made as a result of large cardiovascular outcomes trials. Though randomized controlled trials on insulin, sulfonylureas, and metformin are still limited, cardiovascular outcomes trials on newer glucose-lowering agents have included hundreds of thousands of patients with multiple years of follow-up. The increased risk of thiazolidinediones on heart failure had been well theorized and is now established; however, the increase in heart failure hospitalization with certain dipeptidyl peptidase-4 inhibitors was unexpected. The reasons for discrepancies with regard to heart failure risk with different dipeptidyl peptidase-4 inhibitors remain unclear, and further mechanistic studies are ongoing. The role of glucagon-like peptide-1 receptor agonists among patients with heart failure also remains unclear, and their effects may differ in patients with and without established heart failure, particularly those with decompensated heart failure with reduced ejection fraction.