Recurrent compared to first-time myocardial infarction is associated with worse long-term outcomes

Background Outcomes of first-time myocardial infarction (MI) have improved substantially in recent decades. However, comparative data on long-term outcomes of recurrent MI are lacking. Purpose To compare outcomes of recurrent versus first-time MI in a contemporary nationwide patient cohort. Methods In this nationwide registry-based cohort study, all consecutive patients with a hospitalization for MI in Denmark from 2016 to 2022 were identified. MIs were categorized as first-time or recurrent. Outcomes of interest were all-cause death, heart failure (HF) hospitalization, and (subsequent) recurrent MI. Outcomes were compared for first-time versus recurrent MI. Absolute risk of death was calculated using the Kaplan-Meier estimator and risk of HF hospitalization and recurrent MI were calculated using the Aalen-Johansen method with death as a competing risk. Cox proportional hazards regression was used to calculate hazard ratios (HR) adjusted for age, sex, and comorbidities. Logistic regression adjusted for age and sex was used to calculate odds ratios (OR) for invasive procedures during MI hospitalization and redemption of prescriptions for lipid-lowering and antithrombotic treatment within 30 days of discharge. Results In total, 43,571 patients with first-time MI and 5,028 patients with recurrent MI were included. Patients with recurrent MI were older, more often male, more often on cardiovascular pharmacotherapy at baseline, more likely to have had previous revascularization, and had a substantially higher burden of comorbidities (Table). The 5-year absolute risk of death was 37.9% for recurrent MI versus 24.5% for first-time MI (adjusted HR: 1.07 [1.02-1.13], Figure). The 5-year risk of HF hospitalization was 11.9% for recurrent MI versus 6.5% for first-time MI (adjusted HR: 1.20 [1.09-1.31]). For subsequent recurrent MI, the 5-year absolute risk was 17.0% for recurrent MI versus 9.5% for first-time MI (adjusted HR: 1.59 [1.47-1.71]). Patients with recurrent MI compared to first-time MI were less likely to receive invasive procedures during hospitalization: coronary angiogram, 79.2% versus 85.6%, p<0.001, OR 0.75 (0.69-0.81) and percutaneous coronary intervention, 56.3% versus 64.7%, p<0.001, OR 0.74 (0.70-0.79). Likewise, patients with recurrent MI were less likely to redeem prescriptions for lipid-lowering (OR 0.49 [0.46-0.52]) and antithrombotic (OR 0.74 [0.68-0.79]) treatment within 30 days of discharge from hospital. Conclusion Patients with recurrent MI had a substantially higher risk of adverse long-term outcomes compared to patients with first-time MI. However, the increased risk of death and HF associated with recurrent MI diminised substantially when accounting for differences in age, sex, and comorbidity. The remaining gap may be partially explained by differences in the use of guideline-directed treatment and management.