Abstract 9407: Long-Term Outcomes of Hospitalized Acute Myocarditis: A Korean Nationwide Data in the Pre-COVID-19 Era

Abstract

Introduction: Acute myocarditis is extremely heterogenous in causal agents, clinical courses, and geographic regions. There is little long-term outcomes data for acute myocarditis prior to the COVID-19 pandemic. Hypothesis: The clinical profile of acute myocarditis would differ according to age at presentation. Methods: A retrospective nationwide cohort study was performed. All patients aged 20-79 who were hospitalized for acute myocarditis without underlying cardiac diseases from 2006 to 2018 in Korea. Complicated phenotype was defined as requiring hemodynamic or major organ support. Over 10 years, all-cause mortality and acute myocarditis-driven excess mortality were evaluated according to young-adult (20-39 years), mid-life (40-59 years), and older-adult (60-79 years) age groups. Results: Among 2988 patients (mean age 51.0 years), 362 (12.1%) were of complicated phenotype. All-cause death at 30 days occurred in 40 (4.7%), 52 (4.8%), and 105 (10.0%) patients in the young-adult, mid-life, and older adult groups, respectively (Figure A). Most short-term deaths occurred within 37 days of admission, primarily in the complicated phenotype. However, higher excess mortality compared to the age- and sex-matched general population remained over the 10-year follow-up even in younger patients with non-complicated phenotypes (Figure B). Conclusions: In patients with de novo acute hospitalized myocarditis, short-term mortality is high both in young and older adults, particularly those with advanced age, non-cardiac comorbidities, and severe clinical presentation. Furthermore, long-term excess mortality remains high over 10 years after index hospitalization. A cardiac monitoring strategy should be discussed for post-myocarditis patients against the long-term risk.