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Feasibility of diagnosing chronic myocarditis by endomyocardial biopsy
N Kubo1, S Morimoto, S Hiramitsu
1Department of Internal Medicine, Fujita Health University School of Medicine, Toyoake, Aichi, Japan.
Insights
Diagnosing chronic myocarditis via endomyocardial biopsy is challenging due to sampling errors. Lymphocyte clusters, key indicators, are often missed, potentially leading to missed diagnoses even with multiple tissue samples.
Area of Science:
- Cardiology
- Pathology
- Immunology
Background:
- Chronic myocarditis is characterized by lymphocyte clusters in myocardial tissue.
- Endomyocardial biopsy is a diagnostic tool, but specimen size is limited (2mm x 3mm).
- Autopsy studies reveal lymphocyte clusters in chronic myocarditis, unlike acute cases.
Purpose of the Study:
- To evaluate the diagnostic accuracy of endomyocardial biopsy for chronic myocarditis.
- To determine if lymphocyte clusters, indicative of chronic myocarditis, can be reliably detected in biopsy samples.
- To assess the impact of sampling errors on diagnosing chronic myocarditis via biopsy.
Main Methods:
- Analysis of H&E stained endomyocardial biopsy specimens from seven patients with confirmed chronic myocarditis.
- Random selection of five biopsy sites each from the right and left ventricles.
- Microscopic examination at 400-fold magnification to quantify lymphocytes and identify clusters (≥20 lymphocytes/field).
Main Results:
- A mean of 5 or more lymphocytes/field was observed in three right ventricular samples and one left ventricular sample.
- Lymphocyte clusters (≥20/field) were found in 42.8% of right ventricular samples and 14.3% of left ventricular samples.
- Degenerative changes and fibrosis were associated with lymphocyte clusters, supporting myocarditis diagnosis.
Conclusions:
- Endomyocardial biopsy may miss diagnoses of chronic myocarditis due to sampling errors.
- Even with multiple biopsy sites, approximately half of chronic myocarditis cases could be missed.
- The small size of biopsy specimens poses a significant limitation for detecting localized lymphocyte clusters.
Abstract:
In studies of all the layers of autopsied hearts from patients with chronic myocarditis, local clusters of lymphocytes are frequently noted, in contrast with hearts obtained from patients with acute myocarditis. Myocardial biopsy specimens, however are no larger than about 2mm x 3mm. With this in mind, the present study was undertaken to determine whether chronic myocarditis can be diagnosed by endomyocardial biopsy. Specimens were obtained from seven patients in whom chronic myocarditis was confirmed by the clinical course and by autopsy findings. In H&E stained specimens, sites corresponding to the biopsy sites in both ventricles (right ventricular free wall, right ventricular side of the ventricular septum, left ventricular lateral wall) were selected at random (five sites each from the right and left ventricles in each patient) and examined under a light microscope. A mean of 5 or more lymphocytes per visual field (by light microscopy at 400-fold magnification), a proposed quantitative diagnostic criterion of myocarditis, was noted in the right ventricle in three patients (5 lymphocytes in two patients and 6 in one patient) and in the left ventricle in one patient (5 lymphocytes). Also, when the presence of lymphocyte clusters, considered to be a characteristic feature of chronic myocarditis, was determined, clusters of 20 or more lymphocytes per visual field were found in the same patients as those mentioned above, namely, in three patients (42.8%) in the right ventricle, as mentioned above, and in one patient (14.3%) in the left ventricle. At the sites of these lymphocyte clusters. findings such as degenerative changes of the myocardial cells and interstitial fibrosis were also associated, making possible a diagnosis of myocarditis. Therefore, in chronic myocarditis, even if five specimens are obtained by right ventricular biopsy, in approximately one half of patients the diagnosis of chronic myocarditis will be missed because of sampling errors.