Histopathology of the Cardiac Conduction System in the Investigation of Sudden Unexpected Death

Abstract

When a gross and microscopic autopsy, drug screen, and past medical history fail to yield a cause of death, the forensic pathologist may opt to study the cardiac conduction system. This paper describes the excision of the SA (sinoatrial) node and AV(atrioventricular) node-containing areas of the heart and the microscopic appearance of normal SA and AV nodes, His bundle and bundle branches. Conduction system findings that have been reported to be significant include fibromuscular hyperplasia (often mislabeled dysplasia) of the SA and AV nodes arteries, persistent fetal dispersion of the AV node and His bundle, accessory pathways, ganglionitis and neuritis near the SA node, fibrosis and fatty infiltration of the conducting tissue, AV node tumor, left-sided His bundle, and AV node fibrosis. In an otherwise normal autopsy, AV node tumors, severe fibromuscular hyperplasia of the AV node artery and AV node fibrosis are sufficient to cause death. Other findings, particularly Mahaim tracks, are competent causes of death if they correlate with premortem electrocardiographic findings. Conduction system examination, although a low-yield procedure, is a worthwhile endeavor. Care must be taken to not overestimate the significance of the findings.

Evaluation Of Cardiac Conduction System In Sudden Deaths

“…We think that it may be a result of the differences between the regional dietary habits as well as the higher average age in our study (2,(12)(13)(14)28 (12,13,18,29 (4,13,(30)(31)(32)(33)(34) (14,21,(42)(43)(44) (2,13,16,26,27,46 …”

Histologic Examination of the Heart in the Forensic Autopsy

“…Once thought to be mesothelial in origin, they are now considered to be endodermal rests and the term “mesothelioma” is no longer used. Histologically, these tumors consist of variable-sized cysts lined with cuboidal, transitional, or squamous cells in a background of dense fibrosis (Image 51) (31, 32).…”

“…It is typified by nonatherosclerotic luminal narrowing of this small artery by intimal and medial thickening (Image 54). Several studies have concluded that severe (>75%) narrowing of the AV nodal artery is significant enough to explain sudden cardiac death, with a proposed mechanism of AV nodal ischemia (32, 33).…”

Cartilaginous Metaplasia Involving the Atrioventricular Node and Bundle of His Contributing to Sudden Early Neonatal Death

“…After excision, serial sections perpendicular to the tricuspid annulus should be made. 12 Trichrome stain is highly recommended to better appreciate the cardiac conduction system.…”