Study on existence of inflammation in the myocardium in unequivocal acute traumatic deaths

Novel Immunohistochemical and Morphological Approaches in a Retrospective Study of Post-Mortem Myocarditis

Background and Objectives: This study presents a retrospective analysis of 26 autopsy cases from a single centre, primarily focusing on forensic cases, with a majority of male individuals. Materials and Methods: We systematically analysed autopsy reports and cardiac tissue slides using haematoxylin-eosin stain and immunohistochemistry for CD3, CD163, and IL-6. The histological assessment evaluated key variables such as inflammation severity, necrosis, and background changes using a standardised grading system. Quantitative analysis of immunohistochemical markers was performed, calculating the percentage of positively stained cells within the inflammatory infiltrate. Results: The average age was 51.6 years, slightly skewed towards older males. The fatalities varied widely, with sudden death and drug abuse being the most common conditions linked to myocarditis findings on histological examination. A strong correlation was found between the severity of inflammation (measured by size within a myocardium section) and the scoring system based on the number of inflammatory foci per section (p ≤ 0.001). Most cases showed mild to minimal fibrosis, with some exhibiting moderate to severe fibrosis, arteriosclerosis, and myocyte hypertrophy. The presence of protein CD3 in the inflammatory infiltrate revealed a moderate inverse correlation between the CD3 values and the severity of inflammation and necrosis, and a strong inverse correlation with neutrophil levels. CD3 levels were higher in sudden death cases and lower in cases with numerous inflammatory foci, highlighting the discreet nature of lymphocytic myocarditis. Macrophage presence, assessed using CD163, showed a moderate inverse correlation with neutrophil levels and significant differences between sudden death and non-sudden death cases. Macrophage-rich inflammation was observed in cases with pneumonia/bronchopneumonia-associated lesions. IL-6 expression showed a moderate direct correlation with inflammation severity (p = 0.028), severity of necrosis (p = 0.005), and the number of inflammatory foci per section (p = 0.047). A moderate inverse correlation was found between CD3 and IL-6 expression (p = 0.005). Conclusions: These findings highlight the need for a unique immunohistochemical approach in forensic cases of myocarditis, differing from guidelines for endomyocardial biopsies due to diverse inflammatory cells. The study suggests exploring inflammatory chemokines within myocarditis foci for their significance in clinical scenarios. Specifically, IL-6, a crucial pro-inflammatory interleukin, correlated significantly with the severity of inflammation and necrosis (p < 0.05). This study provides novel and valuable insights into the histopathological and immunological markers of myocarditis in autopsy cases.

Myocarditis in the forensic setting

Diagnosis of myocarditis as the cause of death in the forensic setting at post-mortem is currently determined by a forensic pathologist. There is no systematic method for diagnosis and thus the determination is subject to inter-observer variability and is often non-reproducible. The primary aim of this study was to investigate the differences in the amount of inflammation between cases where myocarditis was deemed the cause of death, compared to cases where myocardial inflammation was incidentally present at autopsy, but not determined to be the cause of death. Participants were sourced from the Victorian Institute of Forensic Medicine (VIFM) database, from full autopsies conducted on reportable death in Victoria, Australia between the years 2011 and 2021. Cases of fatal myocarditis were significantly more likely to experience infection-like symptoms prior to death, and to be in hospital at the time of death. Histopathological examination revealed fatal cases had a significantly higher inflammatory index compared to the incidental group. Lethal cases were also significantly more likely to have myocyte necrosis, and a diffuse pattern of inflammation. There are significant differences between cases where myocardial inflammation has been determined to be the cause of death and cases where inflammation in the myocardium was an incidental finding. These results could be used in the forensic autopsy to help pathologists determine if inflammation should be considered fatal or incidental.

Myocarditis in the forensic setting - a review of the literature

Diagnosis of myocarditis as the cause of death at post-mortem is currently determined by a forensic pathologist. There is no systematic method for diagnosis and thus the determination is subject to inter-observer variability and is non-reproducible. Postmortem studies often rely on the clinical method of diagnosis, which is inaccurate. Furthermore, there is no current standardized method of distinguishing between myocarditis as cause of death, and myocardial inflammation as an incidental finding post-mortem. Only a few studies have investigated a method of quantifying this difference using variables such as number of inflammatory cells and presence of myocyte necrosis, however, there are several limitations hindering the reproducibility of this research. This review investigates the current practices and limitations associated with the diagnosis of myocarditis as cause of death in the autopsy setting.