Long-Term Prognosis and Early Clinical Predictors in Acute Myocarditis: Insights from a 10-year, Unselected Hospital Cohort

Background

Acute myocarditis (AM) is an inflammatory cardiac condition with variable prognosis, ranging from complete recovery to progressive heart failure (HF) or death. While advances in diagnostics, such as high-sensitivity troponins and cardiac magnetic resonance imaging (CMR), have facilitated detection of milder cases, prognostic insights across unselected, real-world populations remain limited.

Methods

In this retrospective cohort study, we analyzed 471 consecutive patients hospitalized with a discharge diagnosis of AM between 2009 and 2019. Inclusion was based on clinical diagnosis. Baseline clinical features, laboratory data, and imaging results were extracted and systematically reviewed. The primary composite outcome comprised all-cause mortality, heart transplantation, use of mechanical circulatory support, new-onset HF, ventricular arrhythmias, and cardiac device implantation.

Results

The median age was 34 years, 32% were female. Chest pain was the predominant presenting symptom (87%), while ST-segment elevation was observed in 48% of cases. At admission, 24.2% of patients had hypokinesia on echocardiography, and 11.6% had a left ventricular ejection fraction (LVEF) <50%. Within the first year of follow-up, 41 patients (8.7%) experienced the composite outcome. Older age, dyspnea at presentation, and elevated biomarkers were associated with adverse events in the first year. Over a median follow-up of 8.2 years, multivariable analysis revealed age (HR 1.05 per year, 95% CI: 1.03–1.07, p<0.001), signs of HF (HR 3.27, 95% CI: 1.25–8.52, p=0.015), and hypokinesia on echocardiography (HR 19.77, 95% CI: 4.10–95.36, p<0.001) as independent predictors of poor outcomes. No sex-based difference in the primary outcome was observed (HR 0.78, 95% CI: 0.31-1.96, p=0.592) despite different clinical presentation.

Conclusions

In this real-world, decade-long cohort, the majority of patients had favorable outcomes. However, a small subset experienced poor outcomes in both the short and long term, highlighting the need for early risk stratification and targeted management of high-risk individuals.

What is new?

• This is one of the largest real-world cohorts (n = 471) of patients hospitalized with acute myocarditis (AM) diagnosed through clinical judgment, CMR, or EMB over a 10-year period.

• Unlike prior studies, inclusion was not limited to CMR-or biopsy-confirmed cases, offering a more representative clinical picture.

• Most patients (87.9%) had favorable long-term outcomes; early adverse events were significantly associated with: older age; heart failure signs at admission and regional hypokinesia.

What are the clinical implications?

• Bedside clinical features, particularly heart failure symptoms and echocardiographic hypokinesia are powerful early predictors of poor prognosis and can guide triage and monitoring decisions.

• Patients without chest pain, or presenting with dyspnea, elevated NT-proBNP, and regional wall motion abnormalities, are at higher risk and may require closer follow-up.

• This study offers a more inclusive and practical understanding of AM prognosis and supports risk-adapted strategies in real-world cardiology.