Myocardial Inflammation, Cellular Death, and Viral Detection in Sudden Infant Death Caused by SIDS, Suffocation, or Myocarditis

Abstract

ABSTRACT:The significance of minor myocardial inflammatory infiltrates and viral detection in SIDS is controversial. We retrospectively compared the demographic profiles, myocardial inflammation, cardiomyocyte necrosis, and myocardial virus detection in infants who died of SIDS in a safe sleep environment, accidental suffocation, or myocarditis. Formalin-fixed, paraffin-embedded myocardial sections were semiquantitatively assessed for CD3 lymphocytes and CD68 macrophages using immunohistochemistry and for cardiomyocyte cell death in H&E-stained sections. Enteroviruses and adenoviruses were searched for using PCR technology. The means of lymphocytes, macrophages, and necrotic cardiomyocytes were not statistically different in SIDS and suffocation cases. Enterovirus, not otherwise specified, was detected in one suffocation case and was the only virus detected in the three groups. Very mild myocardial lymphocyte and macrophage infiltration and scattered necrotic cardiomyocytes in SIDS are not pathologic, but may occur after the developing heart is exposed to environmental pathogens, including viruses. (Pediatr Res 66: 17-21, 2009)

Review of immunological and virological aspects as contributory factors in Sudden Unexpected Death in Infancy (SUDI)

“…Krous et al [14] acknowledged that histological evidence of severe myocardial inflammation is easily attributed to myocarditis, but when very mild myocardial inflammation is detected, the significance remains questionable and could even possibly be normal findings when infants are exposed to environmental pathogens. To observe inflammatory infiltrations the appropriate chemo-attractant signals are required to facilitate migration of these cells to sites of infection.…”

“…The presence of viral pathogens in lung tissue from SIDS cases is not always indicative of cause of death, for example dormant CMV has been found in numerous infants and babies without any pathological manifestation [11]. Fodha et al [13] found that high nasopharyngeal RSV viral loads were shown to be a strong predictor of disease severity in infants, but a specific 6 viral load that is required for respiratory infections to be deemed a significant contributing factor in causing death is still undefined [14]. Weber & Sebire [15] suggested investigating the systemic responses to pathogens isolated instead of relying only on detection.…”

Myocarditis in Childhood: An Update on Etiology, Diagnosis and Management

“…Previous studies have implicated the myocarditis as the cause of sudden death (Friedman et al, 1998, Bowles et al, 2003. In the retrospective study of Krous et al, they evaluated the infants who died of sudden death infant syndrome in a safe sleep environment, accidental suffocation or myocarditis were assessed, and they have noticed the manifestation of scattered inflammatory cells and necrotic myocyte were noticed (Krous et al, 2009). From this observation, they suggested that few scattered inflammation and necrotic myocyte were normal finding in the developing heart exposed to new environmental pathogens.…”

Letter to Editor

“…They used MAb to CD45RO to identify T lymphocytes in the myocardium in their study (1); however, this antibody may identify macrophages and Langerhans cells (2); other studies have also shown a lack of specificity for T lymphocytes (3). CD45RO lymphocytes, the memory T lymphocytes, are a subset of the total T-lymphocyte population that includes CD45RA (or naïve) T lymphocytes.…”

“…To the Editor: In the article titled "Myocardial inflammation, cellular death, and viral detection in sudden infant death caused by SIDS, suffocation, or myocarditis," Krous et al (1) presented results concerning cases of suspected SIDS (n ϭ 24), suffocation (n ϭ 25), and myocarditis (n ϭ 4). Their data indeed did not confirm the findings of our study published in this journal (2), possibly due to technical and analytical differences between the two studies.…”