September 10, 2026Circulation Journal0 citationsOpen Access
Endomyocardial Biopsy and Clinical Outcomes in Acute Myocarditis ― Multicenter Cohort Study ―
Key Result
Endomyocardial biopsy was associated with a significantly lower risk of in-hospital death (HR 0.44) compared to no biopsy in patients with acute myocarditis.
Key Points
- To evaluate the prognostic impact of endomyocardial biopsy on in-hospital and long-term clinical outcomes in patients with acute myocarditis, with a particular focus on fulminant presentations.
- Multicenter cohort study across 7 hospitals evaluating 841 patients with acute myocarditis who either underwent endomyocardial biopsy (n=268) or did not (n=573).
- Assessed primary endpoint of in-hospital death and a secondary composite endpoint (all-cause death, cardiac transplantation, or left ventricular assist device implantation) over a median follow-up of 447 days.
- In-hospital mortality was significantly lower in the biopsy group compared to the non-biopsy group overall (6.3% vs. 11.5%; P=0.019) and among patients with fulminant myocarditis (11.3% vs. 23.7%; P=0.002).
- Multivariable analysis confirmed endomyocardial biopsy was independently associated with lower in-hospital mortality in both the overall cohort and the fulminant myocarditis subgroup.
- Over long-term follow-up, the secondary composite outcome was significantly lower in the biopsy group among patients with fulminant myocarditis (P=0.031).
Study Design
Type
Cohort (n=841)
Multicenter
Yes
Structured PICO
Does endomyocardial biopsy improve clinical outcomes in patients with acute myocarditis?
P
Population
841 patients with acute myocarditis, including those with fulminant presentation, across 7 tertiary hospitals in Korea, followed for a median of 447 days.
E
Exposure
Endomyocardial biopsy (n=268)
C
Comparator
No endomyocardial biopsy (n=573)
O
Outcome
In-hospital deathhard clinical
Performing an endomyocardial biopsy in patients with acute myocarditis is associated with lower in-hospital mortality and improved long-term outcomes, particularly in those with fulminant myocarditis.
Main Result
Hazard Ratio: 0.44 (95% CI 0.26–0.75)
Absolute Event Rate: 6.3% vs 11.5%
p-value: p=0.003
Limitations
- Retrospective observational design introduces potential residual confounding and selection bias.
- A substantial proportion of patients were included without histopathologic confirmation or CMR-compatible findings (classified as possible myocarditis).
- Potential immortal time bias, as patients must survive long enough to undergo the procedure.
- Procedure-related complications of EMB were not systematically captured.
- Myocardial viral genome status was not assessed.
- Small number of patients with eosinophilic and giant cell myocarditis limited robust subtype-specific analyses.
Abstract
Background: Endomyocardial biopsy (EMB) remains the gold standard for diagnosing acute myocarditis (AM); however, its prognostic value has not been fully established. We investigated the prognostic impact of EMB, with a focus on fulminant myocarditis (FM). Methods and Results: We included 841 AM patients across 7 hospitals who were categorized having undergone EMB (n=268) or not (n=573). The primary outcome was in-hospital death; the secondary outcome was a composite of all-cause death, cardiac transplantation, or left ventricular assist device implantation. In-hospital mortality was lower in the EMB group (6.3% vs. 11.5%; P=0.019), with a similar reduction in the EMB group among patients with FM (11.3% vs. 23.7%; P=0.002), despite a higher rate of extracorporeal membrane oxygenation. During a median follow-up of 447 days, the composite outcome was also lower in the EMB group among patients with FM (P=0.031). In multivariable analyses, EMB was independently associated with lower in-hospital mortality in both the overall cohort and the FM subgroup. Outcomes did not differ substantially across histopathologic subtypes, although patients with giant cell myocarditis had a worse prognosis. Conclusions: In patients with AM, EMB was associated with lower in-hospital mortality and improved long-term outcomes, particularly among those with FM. Further well-designed prospective studies are warranted to evaluate the clinical impact of EMB and its potential role in improving outcomes.
Cite This Study
Hyun et al. (2026) conducted a cohort in Acute myocarditis (n=841). Endomyocardial biopsy vs. No endomyocardial biopsy was evaluated on In-hospital death (HR 0.44, 95% CI 0.26-0.75, p=0.003). Endomyocardial biopsy was associated with a significantly lower risk of in-hospital death (HR 0.44) compared to no biopsy in patients with acute myocarditis.