Design and rationale of the myocardial infarction and new treatment with metformin study (MIMET) - Study protocol for a registry-based randomised clinical trial.

Aims: To investigate if addition of metformin to standard care (life-style advice) reduces the occurrence of cardiovascular events and death after myocardial infarction (MI) in patients with newly detected prediabetes.

Methods: The Myocardial Infarction and new treatment with Metformin study (MIMET) is a large multicentre registry-based randomised clinical trial (R-RCT) within the SWEDEHEART registry platform expected to include 5160 patients with MI and newly detected prediabetes (identified with fasting blood glucose, HbA1c or 2-h glucose on oral glucose tolerance test) at ∼20 study sites in Sweden. Patients 18-80 years, without known diabetes and naïve to glucose lowering therapy, will be randomised 1:1 to open-label metformin therapy plus standard care or standard care alone.

Outcomes: Patients will be followed for 2 years for the primary outcome new cardiovascular event (first of death, non-fatal MI, hospitalisation for heart failure or non-fatal stroke). Secondary endpoints include individual components of the primary endpoint, diabetes diagnosis, initiation of any glucose lowering therapy, cancer, and treatment safety. Events will be collected from national healthcare registries.

Conclusions: The MIMET study will investigate if metformin is superior to standard care after myocardial infarction in preventing cardiovascular events in patients with prediabetes (Clinicaltrials.gov identifier: NCT05182970; EudraCT No: 2019-001487-30).