Histopathology of the cardiac conduction system in sudden intrauterine unexplained death

Sudden intrauterine unexplained death (SIUD) is one of the most heartbreaking tragedies that any parent can experience. It remains poorly understood and incompletely examined both morphologically and functionally. The aim of this work is to examine the likely role of cardiac conduction system in relation to sudden and unexplained fetal death.

We analyzed and compared the autopsy results in 15 cases of SIUD (6 males and 9 females, ranging in age from 35 to 40 weeks) and 11 cases of intrauterine explained death (IED). A complete autopsy was performed, focusing on the examination of the cardiac conduction system on serial sections.

The following findings were observed: resorptive degeneration (33% of SIUD, 36% of IED), dispersion or septation of the atrioventricular (AV) junction (60% of SIUD, 64% of IED), islands of the conduction system in the central fibrous body (80% of SIUD, 73% of IED), Mahaim fibers (20% of SIUD), cartilaginous metahyperplasia (20% of SIUD, 18% of IED), an AV node (AVN) tongue (13% of SIUD), hemorrhage of the cardiac conduction system (7% of SIUD, 9% of IED), left-sided bifurcation (7% of SIUD), an intramural right bundle (7% of SIUD), central fibrous body hypoplasia (7% of SIUD), and thickening of the conduction system arteries (13% of SIUD).

Most of the abnormal cardiac conduction findings were detected only in SIUD and were absent in controls, i.e., Mahaim fibers, AVN tongue, left-sided bifurcation, intramural right bundle, and central fibrous body hypoplasia. We are convinced that these cardiac conduction abnormalities, in association with altered neurovegetative stimuli, could underlie potentially malignant arrhythmias.