Abstract 4373227: Thyroid Dysfunction in Acute Myocarditis Is Common; Hypothyroidism Is Associated with Increased Risk of Ventricular Arrhythmias

Introduction: Thyroid dysfunction is frequently observed in patients with acute myocarditis and has been described across multiple studies. Although both conditions may share common pathogenic mechanisms, the prognostic implications of their coexistence remain unclear. Hypothesis: We hypothesize that thyroid dysfunction, is associated with a more severe clinical course and adverse in-hospital outcomes in patients with acute myocarditis. Methods: We conducted a retrospective cohort study of 119 patients diagnosed with acute myocarditis by cardiac magnetic resonance imaging (CMR) at a tertiary care center in Bogotá, Colombia, from January 2022 to December 2024. Sociodemographic data, clinical presentation, laboratory findings, treatment, and in-hospital outcomes were extracted from medical records. Patients were categorized into three groups: euthyroid, hyperthyroid, and hypothyroid. Statistical comparisons were performed using chi-square and ANOVA tests. A p-value <0.05 was considered statistically significant. Results: The mean age was 42.3 years, and 30.2% were female. Thyroid dysfunction was present in 36 patients (30.2%): 17 (14.2%) with hyperthyroidism and 19 (15.9%) with hypothyroidism. There were no significant differences between groups in terms of age, sex, prodromal symptoms, or biventricular function by CMR. However, patients with hypothyroidism had a trend toward longer hospital stays and demonstrated a significantly higher incidence of ventricular arrhythmias during hospitalization (OR: 8.8, 95% CI: 1.80–43.6), despite arrhythmias being an overall infrequent complication. In-hospital mortality was rare across all groups. Conclusions: Thyroid dysfunction, particularly hypothyroidism, is common among patients with acute myocarditis and may be associated with a higher risk of ventricular arrhythmias. These findings highlight the potential prognostic relevance of thyroid function assessment in myocarditis and suggest that concurrent management of thyroid dysfunction could influence clinical outcomes.