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.