Myocardial T-Lymphocytes as a Prognostic Risk-Stratifying Marker of Dilated Cardiomyopathy - Results of the Multicenter Registry to Investigate Inflammatory Cell Infiltration in Dilated Cardiomyopathy in Tissues of Endomyocardial Biopsy (INDICATE Study)

Advancing Precision Medicine in Myocarditis: Current Status and Future Perspectives in Endomyocardial Biopsy-Based Diagnostics and Therapeutic Approaches

The diagnosis and specific and causal treatment of myocarditis and inflammatory cardiomyopathy remain a major clinical challenge. Despite the rapid development of new imaging techniques, endomyocardial biopsies remain the gold standard for accurate diagnosis of inflammatory myocardial disease. With the introduction and continued development of immunohistochemical inflammation diagnostics in combination with viral nucleic acid testing, myocarditis diagnostics have improved significantly since their introduction. Together with new technologies such as miRNA and gene expression profiling, quantification of specific immune cell markers, and determination of viral activity, diagnostic accuracy and patient prognosis will continue to improve in the future. In this review, we summarize the current knowledge on the pathogenesis and diagnosis of myocarditis and inflammatory cardiomyopathies and highlight future perspectives for more in-depth and specialized biopsy diagnostics and precision, personalized medicine approaches.

Diagnosing myocarditis in endomyocardial biopsies: survey of current practice

BACKGROUND

Dallas criteria (DC) and European Society of Cardiology criteria (ESCC) have provided valuable frameworks for the histologic diagnosis and classification of myocarditis in endomyocardial biopsy (EMB) specimens. However, the adaptation and the usage of these criteria are variable and depend on local practice settings and regions/countries. Moreover, several ancillary tests that are not included in the current criteria, such as immunohistochemistry (IHC) or viral polymerase chain reaction (PCR), have proven useful for the diagnosis of myocarditis.

METHOD

As a joint effort from the Association for European Cardiovascular Pathology (AECVP) and the Society for Cardiovascular Pathology (SCVP), we conducted an online survey to understand the current practice of diagnosing myocarditis.

RESULT

A total of 100 pathologists from 23 countries responded to the survey with the majority practicing in North America (45%) and Europe (45%). Most of the pathologists reported to examine less than 200 native heart biopsies per year (85%), and to routinely receive 3-5 fragments of tissue per case (90%). The number of hematoxylin-eosin-stained levels for each case varies from 1 to more than 9 levels, with 20% of pathologists routinely asking for more than 9 levels per case. Among the 100 pathologists, 52 reported to use the DC alone, 12 the ESCC alone, 28 both DC and ESCC and 8 reported to use neither the DC nor the ESCC. Overall, 80 pathologists reported to use the DC and 40 the ESCC. Use of DC alone is more common among North American pathologists compared to European ones (80% vs 32.6%) while use of ESCC alone is more common in Europe (20.9% vs 2.5%). IHC is utilized in either every case or selected cases by 79% of participants, and viral PCR is performed by 35% of participants. Variable terminologies are used in reporting, including both histological and clinical terms. The diagnosis of myocarditis is rendered even in the absence of myocyte injury (e.g., in cases of borderline or inactive/chronic myocarditis) by 46% respondents. The majority of the participants think it is time to update the current criteria (83%).

CONCLUSIONS

The survey data demonstrated that pathologists who render a myocarditis diagnosis practice with variable tissue preparation methods, use of ancillary studies, guideline usage, and reporting. This result highlights the clinically unmet need to update and standardize the current diagnostic criteria for myocarditis on EMB. Additional studies are warranted to establish standard of practice.