Prognostic Value of QRS Duration in Acute Myocarditis: Insights from a Multicenter Cohort Study

AIMS: Prolonged QRS duration is a known prognostic marker in cardiovascular disease, yet its role in acute myocarditis remains uncertain. We examined its association with outcomes in a multicentre myocarditis cohort. METHODS AND RESULTS: We analysed data from 925 patients diagnosed with acute myocarditis between 2001 and 2023 at eight tertiary centres in South Korea. Patients were stratified into three groups based on the maximum QRS duration during hospitalization: <100, 100-120, and >120 ms. The primary outcome was a composite of all-cause mortality, ventricular assist device implantation, and heart transplantation during the follow-up period. Of 925 patients, 250 (27.0%) had QRS >120 ms, 212 (22.9%) 100-120 ms, and 463 (50.1%) < 100 ms. Median follow-up was 37.2 months, QRS duration was significantly associated with the composite outcome on restricted cubic spline analysis (hazard ratio [HR] per 10 ms increase = 1.101, 95% confidence interval [CI] 1.049-1.156, P < 0.001). The QRS duration >120 ms group demonstrated a significantly higher incidence of the primary outcome compared to both the QRS 100-120 and <100 ms groups (P < 0.001). In multivariable Cox regression, prolonged QRS duration, older age, chronic kidney disease, diabetes mellitus, reduced left ventricular ejection fraction (<35%), and higher peak creatine kinase-MB were independent predictors of the primary outcome. CONCLUSION: Prolonged QRS duration, a readily available electrocardiogram (ECG) marker, was independently associated with adverse outcomes in acute myocarditis. Serial ECG monitoring may provide a simple and practical tool for early risk stratification and management, including patients with fulminant myocarditis. CLINICAL TRIAL REGISTRATION: Multicenter Retrospective Observational Study of Acute Myocarditis in Korea, NCT05933902.