Incident heart failure and related outcomes in survivors of acute myocardial infarction within the first year in Sweden across 25 years, between 1997 and 2022

Background and purpose: The widespread adoption of percutaneous coronary intervention (PCI) and guideline-directed medical therapy in acute myocardial infarction (AMI) has not prevented the persistent, common occurrence of subsequent chronic heart failure (HF). However, existing data regarding the incidence and timing of post-myocardial infarction (MI) HF have demonstrated inconsistencies. This study will thus characterize the incidence, timing, and associated outcomes of HF as a post-MI complication. Methods: This study, a nationwide, retrospective, observational register-based cohort study of patients experiencing a first MI, leverages a comprehensive Swedish registry spanning 2 decades (1997–2022) to provide robust, contemporary data. The only inclusion criterion was a first-position inpatient diagnosis of AMI from 1997 to 2022. We assessed the incidence of HF at 0–3 and 4–12 months post-MI, as well as all-cause mortality within 2 years post-MI, as primary endpoints. Results: This study included 384,145 participants with a mean age of 71.6 ± 12.7 years, of whom 62.1% were male. Within 1 year of MI, 22.4% of patients developed HF, 19.0% (72,978 individuals) experienced HF within the first 3 months, and an additional 3.4% (12,976 individuals) developed HF between 4 and 12 months post-MI. Over the past 2 decades, the incidence of HF within 3 months post-MI has remained relatively stable, ranging from 18.4% in 1997 (crude event rate: 102.6, 95% confidence interval [95% CI]: 99.0–106.2 per 100 person-years) to 20.1% in 2022 (crude event rate: 102.0, 95% CI: 97.8–106.4). Incidence within 3 months was lower in men than in women and was approximately three times higher in individuals aged ≥75 years compared to those under 65. The incidence of HF between 4 and 12 months post-MI was lower than during the initial 3-month period. Patients who developed HF after MI had a significantly higher risk of mortality within 2 years. The hazard ratio (HR) for mortality was 2.05 (95% CI: 2.02–2.08, P < 0.0001) for those who developed HF within 0–3 months and 4.00 (95% CI: 3.86–4.15, P < 0.0001) for those with HF onset between 4 and 12 months, compared to patients who did not develop HF post-MI. Mortality within two years post-MI was at least twice as high as in those without HF, with the greatest incidence observed in the first 3 months. Although the mortality rates declined over time, the reduction was less marked in women than in men especially in the group with HF 4–12 months. Alongside this overall decline in mortality, the influence of age on the mortality has increased. Conclusions: Our large-scale, 25-year population-based study of patients experiencing their first MI demonstrates that HF remains a prevalent and prognostically significant complication post-MI, particularly in the early post-infarction period and among female and elderly patients. These findings highlight the need for improved preventive strategies against post-MI HF and the implementation of tailored interventions targeting high-risk sub-groups.