Metformin use at first myocardial infarction increased risk of cardiovascular disease

Takeaway

• In patient with type 2 diabetes mellitus (T2DM), metformin use at the time of first acute myocardial infarction (AMI) was associated with an increased risk for cardiovascular disease (CVD) and death.
• However, metformin use post-AMI might be beneficial in patients with T2DM.

Why this matters

• Findings warrant further randomised controlled trials, especially in view of emerging evidence of cardioprotection from sodium-glucose co-transporter-2 inhibitors.

Study design

• Study included 4030 patients with T2DM and incident AMI who were prescribed metformin (n=2576) or another oral hypoglycaemic drug (n=1454).
• Primary outcome: MACEs (AMI requiring hospitalisation, stroke and CV mortality).
• Secondary outcome: heart failure (HF) hospitalisation and all-cause mortality.
• Funding: UK Medical Research Council and others.

Key results

• Metformin use at the time of AMI:
  • After adjustment for confounders, the risk for MACEs was higher in metformin users compared with non-users (HR, 1.09; 95% CI, 1.01-1.19; P=.034).
  • No significant association was observed between metformin use and risk for:
    • CV mortality (HR, 1.06; 95% CI, 0.96-1.17; P=.275),
    • AMI (HR, 1.06; 95% CI, 0.94-1.20; P=.363) and
    • Stroke (HR, 0.99; 95% CI, 0.82-1.19; P=.904).
  • Metformin use was associated with an increased risk for HF hospitalisation (HR, 1.13; 95% CI, 0.98-1.30; P=.098) but not all-cause mortality (HR, 0.97; 95% CI, 0.89-1.04; P=.395).
• Metformin use post-AMI:
  • Metformin use after AMI was linked to reduced risk for all-cause mortality (HR, 0.75; 95% CI, 0.62-0.93; P=.009).
  • No significant association was observed between metformin use and risk for:
    • MACEs (HR, 0.96; 95% CI, 0.78-1.19; P=.732),
    • HF hospitalisation (HR, 0.67; 95% CI, 0.47-1.01; P=.056) and
    • CV mortality (HR, 0.88; 95% CI, 0.67-1.15; P=.345).

Limitations

• Risk of potential bias.