Clinical outcomes associated with recurrent compared to first-time myocardial infarction.

Background

Patients with recurrent myocardial infarction (MI) are a heterogenous group with high comorbidity burden, risk of complex coronary disease, and at risk of poor outcomes. However, contemporary comparative data are lacking.

Methods

Consecutive patients with recurrent MI (defined as a new hospital admission for MI >28 days following a first-time MI) in Denmark between 2015 and 2022 were identified through the nationwide registries and matched 1:1 on age and sex to patients with first-time MI. The primary outcome was a composite of all-cause mortality, hospitalization for heart failure (HHF), and further recurrent MI. Standardized risks with 95% confidence intervals (CI) were estimated using cause-specific Cox regression models with first-time MI serving as the reference group.

Results

A total of 8,397 patients with recurrent MI and 8,397 with first-time MI were included (median age 73, 70.7% male). Patients with recurrent MI had more comorbidities. For the primary composite outcome, patients with recurrent MI had a standardized 1-year risk of 24.0% versus 17.2% among those with first MI (standardized risk ratio [sRR] 1.39 [95% CI: 1.34-1.44]). They also had higher risks of: all-cause mortality, 14.6% versus 11.3% (sRR 1.29 [1.24-1.35]); HHF, 6.6% versus 6.0% (sRR 1.11 [1.00-1.21]), and recurrent MI 6.7% versus 2.2% (sRR 3.01 [2.71-3.45]). Use of guideline-recommended treatments post-dicharge was high, albeit lower than for first-time MI: percutaneous coronary intervention (53.7% versus 64.3%, p<0.001), lipid-lowering treatment (78.1% versus 83.2%, p<0.001), and P2Y12 inhibitor (77.3% versus 82.6%, p<0.001).

Conclusion

Recurrent MI is associated with a higher risk of all-cause mortality, HHF, and further recurrent MI compared with first-time MI.