Endomyocardial Biopsy in Myocarditis: Assessing Safety and Prognostic Implications

In 1986, the Dallas Criteria were introduced and provided a standardized histopathological framework for diagnosing myocarditis [1]. Since then, endomyocardial biopsy (EMB) has long been recognized as the definitive diagnostic tool for myocarditis [2]. Despite its critical role in defining myocardial pathology, the utilization of EMB is often debated due to concerns about procedural risks, limited accessibility, and low sensitivity in patients with patchy involvement [3, 4]. Advances in cardiac imaging modalities, such as cardiac magnetic resonance imaging, have led to EMB being increasingly reserved for cases where non-invasive methods fail to provide a conclusive diagnosis. A scientific statement from the American Heart Association, the American College of Cardiology, and the European Society of Cardiology recommended EMB in select cases [5], particularly in patients presenting with unexplained cardiomyopathy or when EMB results may be helpful in estimating prognosis or guiding the treatment.In this issue, Li et al. [6] present a retrospective cohort analysis of 294 patients with suspected myocarditis, of whom 151 underwent EMB. The authors assessed both the short-term and long-term outcomes of EMB and identified risk factors associated with procedural complications. The results demonstrate that EMB was associated with a 2.0% rate of major complications and a 9.3% rate of minor complications. EMB did not adversely affect short-term cardiac function or prolong hospital stays. The long-term follow-up data suggested that EMB may contribute to improved prognostic outcomes, with a lower incidence of major adverse cardiovascular events and left ventricular dilation compared to patients who did not undergo EMB. Their findings provide valuable insight into the safety and prognostic implications of EMB; however, important methodological concerns warrant further scrutiny when interpreting the results.First, the retrospective, single-center design introduces potential biases in patient selection, data collection, and follow-up assessments. The study mentions that the decision to perform EMB was made based on patient preference and clinical condition, but it does not provide further details. Without a standardized selection process, there is a risk of selection bias affecting the study’s conclusions. Moreover, the exclusion of patients with severe left ventricular dysfunction (left ventricular ejection fraction [LVEF] <30%) may have led to an underestimation of EMB-related risks in higher-risk populations. Another key limitation is the handling of long-term echocardiographic follow-up data. The definition and measurement intervals of left ventricular dilation and LVEF remain vague. The study reports that a decrease in LVEF was more frequent in the non-EMB group compared to the EMB group (25% vs 13%), but it fails to specify the magnitude of decline considered significant or the timeframe over which EF was measured.The long-term follow-up of the study by Li et al. [6] suggests that EMB may contribute to improved prognostic outcomes, potentially due to a more accurate diagnosis that enables targeted treatment modifications, including tailored immunosuppressive or heart failure therapies. However, the study does not explicitly clarify whether the improved outcomes were due to optimized treatment strategies following a confirmed diagnosis. If EMB can alter the long-term prognosis of myocarditis, it may justify its use and the associated risks.In conclusion, the study by Li et al. [6] contributes to the ongoing discussion regarding the role of EMB in myocarditis, reinforcing its diagnostic and prognostic value. However, future research should aim to validate these findings through prospective, multicenter studies with standardized protocols with focusing on refining patient selection criteria, optimizing procedural safety, complication monitoring, and long-term follow-up. Until then, the decision to perform EMB might still remain individualized, weighing its benefits against potential risks on a case-by-case basis.The author has no conflicts of interest to declare.The author did not receive any financial support.M.C. is the sole author and was responsible for conceptualization, writing of original draft, critical revision, and final approval of the manuscript.

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