Histopathology of the cardiac conduction system in sudden intrauterine unexplained death

Sudden unexpected intrapartum death and left ventricular noncompaction involving the right ventricle

Left ventricular noncompaction (LVNC), involving mainly the right ventricle, is a rare form of congenital heart disorder characterized by a developmental arrest in myocardial compaction, resulting in a spongy appearance of the myocardium, mainly of the right ventricle, rarely detected in fetuses. We report the case of a female fetus with a gestational age of 41+4 weeks who came to our attention for intrapartum sudden unexpected death, resulting in stillbirth. The ventricular walls, particularly the right ventricular wall, appeared thick, hypertrabeculated and spongy, leading to the diagnosis of LVNC involving mainly the right ventricle. The atrioventricular node and His bundle presented areas of fetal dispersion and resorptive degeneration; islands of conduction tissue were detected in the central fibrous body. Arcuate nucleus of the brainstem showed bilateral severe hypoplasia. The right bundle branch was hypoplastic. The final cause of death was an electrical conduction disfunction in an LVNC involving mainly the right ventricle. To the best of our knowledge, the herein described case is the first reported observation of sudden intrapartum death from LVNC involving mainly the right ventricle well documented post-mortem with cardiac conduction and brainstem studies. Our findings confirm the need of an accurate post-mortem examination including the study of the cardiac conduction system on serial section in every case of sudden unexpected fetal death, although there are no universally recognized guidelines.

Autopsy for Medical Diagnostics: Finding the Cause of Sudden Unexpected Death through Investigation of the Cardiac Conduction System by Serial Sections

Sudden unexpected death (SUD) is a fatal event that occurs in an apparently healthy subject in a way that such an abrupt outcome could have not been predicted. SUD-including sudden intrauterine unexplained death (SIUD), sudden neonatal unexpected death (SNUD), sudden infant death syndrome (SIDS), sudden unexpected death of the young (SUDY), and sudden unexpected death in the adult (SUDA)-occurs as the first manifestation of an unknown underlying disease or within a few hours of the presentation of a disease. SUD is a major unsolved, shocking form of death that occurs frequently and can happen at any time without warning. For each case of SUD, a review of clinical history data and performance of a complete autopsy, particularly focused on the study of the cardiac conduction system, were carried out according to the necropsy protocol devised by the Lino Rossi Research Center, Università degli Studi di Milano, Italy. Research cases collected and selected for this study were represented by 75 SUD victims that were subdivided into 15 SIUD, 15 SNUD, 15 SUDY, and 15 SUDA victims. After a routine autopsy and clinical history analysis, death remained unexplained, and hence a diagnosis of SUD was assigned to 75 subjects, which included 45 females (60%) and 30 (40%) males ranging in age from 27 gestational weeks to 76 years. Serial sections of the cardiac conduction system disclosed frequent congenital alterations of the cardiac conduction system in fetuses and infants. An age-related significant difference in distribution among the five age-related groups was detected for the following anomalies of the conduction system: central fibrous body (CFB) islands of conduction tissue, fetal dispersion, resorptive degeneration, Mahaim fiber, CFB cartilaginous meta-hyperplasia, His bundle septation, sino-atrial node (SAN) artery fibromuscular thickening, atrio-ventricular junction hypoplasia, intramural right bundle branch, and SAN hypoplasia. The results are useful for understanding the cause of death for all SUD cases that were unexpected and would have otherwise remained unexplained, so as to motivate medical examiners and pathologists to perform more in-depth studies.

Sudden Unexpected Death Associated with Arrhythmogenic Cardiomyopathy: Study of the Cardiac Conduction System

A retrospective study was conducted on pathologically diagnosed arrhythmogenic cardiomyopathy (ACM) from consecutive cases over the past 34 years (n = 1109). The anatomo-pathological analyses were performed on 23 hearts diagnosed as ACM (2.07%) from a series of 1109 suspected cases, while histopathological data of cardiac conduction system (CCS) were available for 15 out of 23 cases. The CCS was removed in two blocks, containing the following structures: Sino-atrial node (SAN), atrio-ventricular junction (AVJ) including the atrio-ventricular node (AVN), the His bundle (HB), the bifurcation (BIF), the left bundle branch (LBB) and the right bundle branch (RBB). The ACM cases consisted of 20 (86.96%) sudden unexpected cardiac death (SUCD) and 3 (13.04%) native explanted hearts; 16 (69.56%) were males and 7 (30.44%) were females, ranging in age from 5 to 65 (mean age ± SD, 36.13 ± 16.06) years. The following anomalies of the CCS, displayed as percentages of the 15 ACM SUCD cases in which the CCS has been fully analyzed, have been detected: Hypoplasia of SAN (80%) and/or AVJ (86.67%) due to fatty-fibrous involvement, AVJ dispersion and/or septation (46.67%), central fibrous body (CFB) hypoplasia (33.33%), fibromuscular dysplasia of SAN (20%) and/or AVN (26.67%) arteries, hemorrhage and infarct-like lesions of CCS (13.33%), islands of conduction tissue in CFB (13.33%), Mahaim fibers (13.33%), LBB block by fibrosis (13.33%), AVN tongue (13.33%), HB duplicity (6.67%%), CFB cartilaginous meta-hyperplasia (6.67%), and right sided HB (6.67%). Arrhythmias are the hallmark of ACM, not only from the fatty-fibrous disruption of the ventricular myocardium that accounts for reentrant ventricular tachycardia, but also from the fatty-fibrous involvement of CCS itself. Future research should focus on application of these knowledge on CCS anomalies to be added to diagnostic criteria or at least to be useful to detect the patients with higher sudden death risks.

Unexpected fatal intramyocardial cartilaginous tumor: pathophysiology, mechanism of death and review of the literature

Intramyocardial cartilage has never been reported in the human heart before. In the literature, the only reported localizations of cartilage in the heart were in the central fibrous body and the valves. We report a case of an unusual presence of cartilage tissue within the myocardial wall of the left ventricle in a 10-year-old boy who died unexpectedly. This case presents an interesting, unusual and apparently asymptomatic sudden cardiac death related to a cartilaginous myocardial tumor. Conducting system disturbance secondary to the myocardial tumor is the probable cause of death. This case is relevant not only for its singularity and originality, but also for the diverse and controversial hypotheses related to the onset of cartilaginous tissue in the myocardial wall. Early detection of this tumor by modern thoracic imaging may have prevented a fatal unexpected outcome.

Dissecting the Cardiac Conduction System: Is It Worthwhile?

BACKGROUND

Pathologic examination of conduction system (CS) is not routinely performed, and histologic changes are mostly reported in forensic practice.

METHODS

We studied the value of dissecting the CS in a cohort of pediatric patients with unexplained sudden death or severe, inexplicable arrhythmias. Histopathologic changes present in CS components were recorded and correlated with findings noted in other cardiac structures.

RESULTS

Twenty-one subjects (11 unexplained sudden deaths and 10 life-threatening arrhythmias) were identified; 18 (86%) had CS pathologic abnormalities. In 13 patients (62%), the CS findings mirrored those found in other cardiac sections (inflammation, allograft vasculopathy, vascular fibromuscular dysplasia, cardiomyopathy-related changes, and tumor/tumor-like conditions). Five cases (24%) had abnormalities restricted to CS (bundle of His [BH] with fibrotic scar and patch material following ventricular septal defect repair, inflammation, BH with fibrosis and calcifications, and intimal fibroplasia of sinoatrial node artery).

CONCLUSIONS

Pathologic changes within the CS are present in a high number of pediatric patients presenting with unexplained sudden death or life-threatening arrhythmias. Frequently, the findings mirror those observed in other cardiac structures. However, in a significant number of cases (24%), the changes are restricted to CS and likely explain the patients' symptoms or cause of death, suggesting that systematic dissection of CS unveils valuable information.

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

Cartilaginous metaplasia involving the atrioventricular (AV) node is an uncommon entity that may cause sudden cardiac death secondary to dysrhythmias. We report 2 autopsy cases of full-term male newborns: 1 stillborn and 1 live-born, with antemortem bradycardia who died in the peripartum period. An examination of the cardiac conduction system in both cases demonstrated extensive cartilaginous metaplasia of the central fibrous body and involvement of the AV node and bundle of His. The cases highlight the recognition of cardiac conduction system anomalies as a cause of sudden perinatal death. In cases of perinatal death with preceding arrhythmia, postmortem sections of the cardiac conduction system are recommended to examine for cardiac conduction system anomaly.

Pathology of unexpected sudden cardiac death: Obstructive sleep apnea is part of the challenge

Unexpected sudden cardiac death (SCD), sudden infant death syndrome (SIDS) and sudden intrauterine unexplained death (SIUD) are major unsolved, devastating forms of death that occur frequently. Obstructive sleep apnea (OSA) has been associated with increased cardiovascular and cerebrovascular morbidity and mortality, including sudden cardiac death (SCD). This editorial will review the pathology of SCD, including sudden infant death syndrome (SIDS) and sudden intrauterine unexplained death (SIUD); OSA with its cardiovascular consequences; the possible link between SCD and OSA, discussing the potential mechanisms underlying these two frequent, but yet overlooked pathologies. Finally, the possible preventive benefits of treating OSA and identifying patients at common risk for OSA and SCD and SIDS-SIUD to prevent unexpected deaths will be discussed. Post-mortem examination is of great importance in every case of SCD sine materia, with examination of the brainstem and cardiac conduction system on serial sections, when general autopsy fails, but it should be stressed that also the investigations of patients suffering from OSA should focus on the possibility of pathological findings in common with cases of SCD.

The use of an osmotic dilator for induction of miscarriage in patients with the second trimester missed miscarriage

AIM

The aim of this study was to assess the outcomes of combined use of dilapan-S and pharmacological induction of miscarriage with mifepristone and misoprostol versus mifepristone and misoprostol only in patients with a second-trimester pregnancy loss.

MATERIALS AND METHODS

Our study included 74 patients with a second-trimester antenatal death who were randomized into two groups to receive pharmacological induction of miscarriage combined with intracervical insertion of dilapan-S (n = 37) or pharmacological induction of miscarriage only (n = 37). Efficacy endpoints included: blood loss volume, length of time between the procedure initiation and complete miscarriage, and the number of complications.

RESULTS

The use of dilapan-S together with mifepristone and misoprostol for induction of miscarriage in the second trimester in women with antenatal fetal death reduced the time from the start of the procedure to complete miscarriage by 1.98-fold. However, the use of dilapan-S did not significantly reduce the odds of such post-procedural complications as hematometra and retention of the products of conception in the uterus (p = .2501).

CONCLUSIONS

Combined management of antenatal pregnancy loss in the second trimester including intracervical insertion of dilapan-S and conventional induction with miscarriage may be considered a valuable clinical strategy. However, future studies should focus on ways to prevent postprocedural complications in this group of women.

Histological topography of the atrioventricular node and its extensions in relation to the cardiothoracic surgical landmarks in normal human hearts

BACKGROUND

Atrioventricular (AV) nodal injury which results in cardiac conduction disorders is one of the potential complications of heart valve surgeries and radiofrequency catheter ablations. Understanding the topography of the AV conduction system in relation to the tricuspid and mitral valves will help in reducing these complications.

METHODS

A tissue block of 3cmx4cm, which contain the AV node, bundle of His and the AV nodal extensions, was excised at the AV septal junction in 20 apparently normal human hearts. The block was divided into three equal segments through vertical incisions perpendicular to the insertion of the septal leaflet of the tricuspid valve. Each segment was processed and stained with H&E and Gomori to study the different parts of the AV conduction system.

RESULTS

The lower pole of the AV node was located vertically above the tricuspid septal leaflet (TSL) in 100% (20/20) of cases and at the level of the muscular interventricular septum in 65% (13/20) of cases. The upper pole of the compact AV node was located at the level of the mitral valve leaflet (MVL) in 50% (10/20) of cases. The penetrating bundle of His was seen at the level of the TSL, while the branching bundle of His was situated 1.9±1.5 mm inferior to the TSL. The right and left posterior extensions of the AV node spanned from the MVL to 2.9±1.3 mm above the TSL.

CONCLUSIONS

A rectangular area (2.5 mm × 12 mm) in the Koch's triangle was devoid of AV nodal tissue and could be labeled as a safe area with no risk of conduction defects during valve surgeries. Information on the separation of AV nodal extensions from the TSL, MVL and muscular interventricular septum may play a crucial role in guiding and improving the safety of radiofrequency ablations.

Update on congenital heart disease and sudden infant/perinatal death: from history to future trends

During the 20th century, expert pathologists contributed an in-depth characterisation of the anatomical pathology and associated pathophysiology of congenital heart disease (CHD). Starting in the 1970s, the reported CHD birth prevalence has been increasing, owing to advances in diagnostic methods. Over the years, surgical treatments have been associated with an enormous reduction of CHD mortality. Advances also have been made in understanding the developmental biology and molecular pathogenesis of CHD. In developed countries, sudden infant death syndrome (SIDS) is the most frequent form of death during the first year of life, with a death rate of 0.42 every 1000 births. Unexpected stillbirth has a six- to eightfold greater incidence than that of SIDS and remains unexplained in 40–80% of cases even after autopsy. Specific environmental risk factors, such as maternal smoking, air and water pollution, food contamination, pesticides, etc, can interact with the genetic constitution in complex ways, which may lead to polymorphisms and/or mutations of specific genes, such as polymorphisms in the serotonin transporter gene 5-HTT, the regulator of the synaptic serotonin concentration. Current directions of research in this area are reviewed.

Anatomopathological changes of the cardiac conduction system in sudden cardiac death, particularly in infants: advances over the last 25 years

Sudden cardiac death (SCD) is defined as the unexpected death without an obvious noncardiac cause that occurs within 1 h of witnessed symptom onset (established SCD) or within 24 h of unwitnessed symptom onset (probable SCD). In the United States, its incidence is 69/100,000 per year. Dysfunctions of the cardiac conduction and autonomic nervous systems are known to contribute to SCD pathogenesis, even if most clinicians and cardiovascular pathologists lack experience with detailed examination of the cardiac conduction system and fail to recognize lesions that are crucial to explain the SCD itself. In this review, we sought to describe the advances over the last 25 years in the study of the anatomopathological changes of the conducting tissue, in SCD, in mature hearts and particularly in sudden infant death syndrome (SIDS) and sudden intrauterine unexpected death syndrome (SIUDS), through the articles published in our journal Cardiovascular Pathology (CVP). We carried out an extensive Medline search to retrieve and review all articles published in CVP in which the sudden unexpected death of one or more subjects believed healthy was reported, especially if associated with lesions of the conducting tissue in settings that revealed no other explained causes of death, particularly in infants and fetuses. The cardiac conduction findings of resorptive degeneration, His bundle dispersion, Mahaim fibers, cartilaginous meta-hyperplasia, persistent fetal dispersion, left-sided His bundle, septation of the bifurcation, atrioventricular node dispersion, sinus node hypoplasia, Zahn node, His bundle hypoplasia, atrioventricular node, and His bundle dualism were similarly detected in SIDS and SIUDS victims.

Sudden fetal death due to dualism of the sino-atrial node

First, we report a sudden fetal death at 33(+3)weeks due to sino-atrial node dualism. The female stillborn was delivered by induced labor. The postmortem examination of the cardiac conduction system revealed a dualism of the sino-atrial node, associated with fragmentation of the atrio-ventricular node and His bundle. These abnormalities of the cardiac conduction system represent the morphological substrate for the development of malignant arrhythmias. In particular, the dualism of the sino-atrial node can cause the dissociation of the longitudinal nodal impulse into two distinct ways of different pulse generation, resulting in supraventricular tachyarrhythmias. This observation suggests new avenues of research on the pathogenesis of the sudden unexpected fetal death. Moreover, our findings confirm the need for an accurate postmortem examination, including serial sectioning of the cardiac conduction system, in every case of unexplained fetal death, following standardized autoptic protocols.

The First 5-Year-Long Survey on Intrauterine Unexplained Sudden Deaths from the Northeast Italy

PURPOSE

Sudden intrauterine unexplained death syndrome (SIUDS) represents one of the main open issues in the scientific and social setting of the modern medicine, and our efforts have aimed to understand its possible causes and risk factors.

METHODS

A 43-case series of consecutive unexplained fetal deaths coming from Northeast Italy, collected in a 5-year period (2011-2015), has been submitted to an in-depth investigation, based on neuropathological and cardiopathological examinations, immunohistochemistry for neuronal nuclear antigen (NeuN), genetic characterization for the serotonin transporter (5-HTT) gene polymorphisms, and toxicological environmental analyses.

RESULTS

The overall survey from the neuropathological findings highlights one or more congenital morphological abnormalities of the autonomic nervous system in 77% of cases of sudden fetal deaths.

CONCLUSIONS

From our results emerges the need to perform a complete autopsy of all SIUDS victims with an in-depth examination of the neuronal centers of the brainstem, which modulate the vital functions.

Congenital central hypoventilation syndrome and sudden infant death syndrome: disorders of autonomic regulation

Long considered a rare and unique disorder of respiratory control, congenital central hypoventilation syndrome has recently been further distinguished as a disorder of autonomic regulation. Similarly, more recent evidence suggests that sudden infant death syndrome is also a disorder of autonomic regulation. Congenital central hypoventilation syndrome typically presents in the newborn period with alveolar hypoventilation, symptoms of autonomic dysregulation and, in a subset of cases, Hirschsprung disease or tumors of neural crest origin or both. Genetic investigation identified PHOX2B, a crucial gene during early autonomic development, as disease defining for congenital central hypoventilation syndrome. Although sudden infant death syndrome is most likely defined by complex multifactorial genetic and environmental interactions, it is also thought to result from central deficits in the control of breathing and autonomic regulation. The purpose of this article is to review the current understanding of these autonomic disorders and discuss the influence of this information on clinical practice and future research directions.

Infant and perinatal pulmonary hypoplasia frequently associated with brainstem hypodevelopment

Recent anatomo-pathological studies have revealed a frequent associated hypoplasia of both arcuate nucleus and lungs in stillbirths. The purpose of this study is to analyze the lung and brainstem development in sudden unexplained perinatal death and sudden infant death syndrome (SIDS). A total of 51 cases were investigated. A complete autopsy was performed in each case. Anatomo-pathologic examination of the central autonomic nervous system included an in-depth study on histological serial sections of the brains where the main structures participating in control of the vital functions are located. The stage of lung development was evaluated by macroscopic and microscopic criteria. In 52.9% of cases, a pulmonary hypoplasia was detected. The pulmonary hypoplasia was significantly more frequent in the SIDS group compared to the sudden perinatal unexplained death groups (p < 0.05). In 72.5% of cases, histological examination of the brainstem on serial sections showed hypodevelopment of the brainstem nuclei, particularly hypoplasia, of the arcuate nucleus (60.8%). In 47.1% of cases, pulmonary hypoplasia was associated with brainstem hypodevelopment.