Sudden Infant Death Syndrome (SIDS): a study of cardiac conduction system

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 infant death syndrome: Melatonin, serotonin, and CD34 factor as possible diagnostic markers and prophylactic targets

Sudden infant death syndrome (SIDS) is one of the primary causes of death of infants in the first year of life. According to the WHO's data, the global infant mortality rate is 0.64-2 per 1,000 live-born children. Molecular and cellular aspects of SIDS development have not been identified so far. The purpose of this paper is to verify and analyze the expression of melatonin 1 and 2 receptors, serotonin (as a melatonin precursor), and CD34 molecules (as hematopoietic and endothelial markers of cardiovascular damage) in the medulla, heart, and aorta in infants who died from SIDS. An immunohistochemical method was used to investigate samples of medulla, heart, and aorta tissues of infants 3 to 9 months of age who died from SIDS. The control group included children who died from accidents. It has been shown that the expression of melatonin receptors as well as serotonin and CD34 angiogenesis markers in tissues of the medulla, heart, and aorta of infants who died from SIDS is statistically lower as compared with their expression in the same tissues in children who died from accidents. The obtained data help to clarify in detail the role of melatonin and such signaling molecules as serotonin and CD34 in SIDS pathogenesis, which can open new prospects for devising novel methods for predictive diagnosis of development and targeted prophylaxis of SIDS.

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.

Comprehensive Analysis of Genes Associated With Sudden Infant Death Syndrome

Background: Sudden infant death syndrome (SIDS) is a tragic incident which remains a mystery even after post-mortem investigation and thorough researches. Methods: This comprehensive review is based on the genes reported in the molecular autopsy studies conducted on SIDS so far. A total of 20 original studies and 7 case reports were identified and included in this analysis. The genes identified in children or adults were not included. Most of the genes reported in these studies belonged to cardiac channel and cardiomyopathy. Cardiac channel genes in SIDS were scrutinized for further analysis. Results: After screening and removing the duplicates, 42 unique genes were extracted. When the location of these genes was assessed, it was observed that most of these belonged to Chromosomes 11, 1 and 3 in sequential manner. The pathway analysis shows that these genes are involved in the regulation of heart rate, action potential, cardiac muscle cell contraction and heart contraction. The protein-protein interaction network was also very big and highly interactive. SCN5A, CAV3, ALG10B, AKAP9 and many more were mainly found in these cases and were regulated by many transcription factors such as MYOG C2C1 and CBX3 HCT11. Micro RNA, "hsa-miR-133a-3p" was found to be prevalent in the targeted genes. Conclusions: Molecular and computational approaches are a step forward toward exploration of these sad demises. It is so far a new arena but seems promising to dig out the genetic cause of SIDS in the years to come.

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.

Chondroid and Osseous Metaplasia of the Central Fibrous Body in Adolescent Hearts with Mutations in TNNI3 and TNNT2 genes

The histological spectrum of the central fibrous body (CFB) of the heart, particularly in humans, is not fully characterized. Herein, we describe the presence of cartilage and bone within the CFB of 2 explanted heart specimens from patients with known mutation-driven cardiomyopathy involving the TNNI3 and TNNT2 genes, review the existing literature on the identified variants particularly TNNI3 (p.Asn185Thrfs*14) and TNNT2 (p.Arg141Trp), and provide insights into the plausible nature of such histopathological observation based on animal studies and the few reported cases in humans.

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.

The autopsy at the time of SARS-CoV-2: Protocol and lessons

A new viral disease named COVID-19 has recently turned into a pandemic. Compared to a common viral pneumonia it may evolve in an atypical way, causing the rapid death of the patient. For over two centuries, autopsy has been recognized as a fundamental diagnostic technique, particularly for new or little-known diseases. To date, it is often considered obsolete giving the inadequacy to provide samples of a quality appropriate to the sophisticated diagnostic techniques available today. This is probably one of the reasons why during this pandemic autopsies were often requested only in few cases, late and discouraged, if not prohibited, by more than one nation. This is in contrast with our firm conviction: to understand the unknown we must look at it directly and with our own eyes. This has led us to implement an autopsy procedure that allows the beginning of the autopsy shortly after death (within 1–2 h) and its rapid execution, also including sampling for ultrastructural and molecular investigations. In our experience, the tissue sample collected for diagnosis and research were of quality similar to biopsy or surgical resections. This procedure was performed ensuring staff and environmental safety. We want to propose our experience, our main qualitative results and a few general considerations, hoping that they can be an incentive to use autopsy with a new procedure adjusted to match the diagnostic challenges of the third millennium.

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Early performed autopsy (within 1-2 hour from death) provides tissue samples for diagnosis and research of quality similar to biopsy or surgical resections.

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Early samples collection reduces post-mortem artifacts, thus preventing the wrong interpretation of the morphological pictures observed.

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Precise autopsy planning prevents risks for the staff.

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.

Right Ventricular Involution: Big Changes in Small Hearts

BACKGROUND

Before birth, the fetal right ventricle (RV) is the pump for the systemic circulation and is about as thick as the left ventricle (LV). After birth, the RV becomes the pump for the lower pressure pulmonary circulation, and the RV chamber elongates without change in its wall thickness. We hypothesize that the fetal RV may be a model of compensated RV hypertrophy, and understanding this process may aid in discovering therapeutic strategies for RV failure.

METHODS

We performed a literature review and identified pertinent articles from 1980 to present.

RESULTS

The following topics were identified to be most pertinent in right ventricular involution: morphologic and histologic changes of the RV, cellular proliferation and terminal differentiation, the effect of stress on RV development, excitation contraction coupling and inotropic response change over time, and the amount of apoptosis through RV development.

CONCLUSIONS

The RV changes on multiple levels after its transition from systemic to pulmonary circulation. Although published literature has variable results due partly from differences between animal models, the literature shows a clear need for more research in the field.

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 Unexplained Nocturnal Death Syndrome in Central China (Hubei): A 16-Year Retrospective Study of Autopsy Cases

A retrospective study was conducted at Tongji Forensic Medical Center in Hubei (TFMCH) from 1999 to 2014. Forty-nine cases of sudden unexplained nocturnal death syndrome (SUNDS) were collected. The SUNDS rate was 1.0% in the total number of cases, in which an incidence was fluctuating over the years. Interestingly, April and January, and 3:00 to 6:00 AM were the peak months and times of death. Among the decedents, farmers and migrant workers accounted for 67.3%. The syndrome predominantly attacked males in their 30s. One victim had sinus tachycardia. Thirteen victims (26.5%) were witnessed and had abnormal symptoms near death. Macroscopically, compared to sudden noncardiac deaths, the weights of brain, heart, and lungs had no statistical difference in SUNDS. Microscopically, the incidence of lung edema (45 cases, 91.8%) was significantly higher in SUNDS group than in the control group (27 cases, 55.1%). 82.9% of 35 SUNDS cases examined displayed minor histological anomalies of the cardiac conduction system (CCS), including mild or moderate fatty, fibrous or fibrofatty tissue replacement, insignificant stenosis of node artery, and punctate hemorrhage in the node area. These findings suggested that minor CCS abnormalities might be the substrates for some SUNDS deaths. Therefore, SUNDS victims might suffer ventricular fibrillation and acute cardiopulmonary failure before death. Further in-depth studies are needed to unveil the underlying mechanisms of SUNDS.

Effect of birth asphyxia on p wave dispersion

OBJECTIVES

To evaluate the cardiac conduction system using P wave dispersion on electrocardiogram and its relationship with the short term mortality and development of arrhythmia in asphyxiated neonates.

METHODS

Thirty term babies with evidence of asphyxia and without any congenital abnormalities were consecutively evaluated as cases. They were compared with thirty healthy term babies without asphyxia. Twelve-lead surface electrocardiography was obtained from all the patients and the controls, and P wave dispersion was calculated according to its definition as the difference between P maximum duration and P minimum duration in 12-lead electrocardiogram.

RESULTS

A statically significant difference of P wave dispersion was observed between the patients and the control group (0.027 ± 0.011 mm/s and 0.016 ± 0.006 mm/s, respectively; P value = 0.0001). The P wave dispersion had a statistically significant correlation with the grade of asphyxia (P = 0.004, r = 0.62), the P wave dispersion had no statistically significant correlation with Apgar scores, short term arrhythmia, and troponin I level in asphyxiated neonates (P < 0.05).

CONCLUSIONS

The P wave dispersion increased in asphyxiated neonates and correlated with grade of asphyxia; however, the increased P wave dispersion was not correlated with the short term mortality, arrhythmia and troponin I level of the asphyxiated neonates.

Intact numbers of cerebellar purkinje and granule cells in sudden infant death syndrome: a stereologic analysis and critical review of neuropathologic evidence

Despite much research during recent decades, the etiology and pathogenesis of sudden infant death syndrome (SIDS) remain unknown. Because of the role of the cerebellum in respiratory and cardiovascular control, it has been proposed that it plays an important role in the pathogenesis of SIDS. To date, 5 postmortem studies on the cerebellum of SIDS cases have yielded conflicting results. Using a rigorous design-based stereologic approach, we investigated postmortem cerebella from 9 SIDS patients who died between 2 and 10 months of age and from 9 age- and sex-matched control children. Neither the volumes of the cerebellar external granule cell layer, molecular layer, internal granule cell layer (including the Purkinje cell layer), and white matter nor the total numbers of Purkinje cells, granule cells in the internal granule cell layer, and the number of granule cells per Purkinje cell showed statistically significant differences between the SIDS cases and the controls. Based on these observations, we conclude that structural alterations in cerebellar development are not involved in the etiology and pathogenesis of SIDS.

Hypoxia at the heart of sudden infant death syndrome?

Sudden infant death syndrome (SIDS) is a significant clinical problem without an accepted pathological mechanism, but with multiple conflicting models. Mutations in a growing number of genes have been found postmortem in SIDS cases, notably genes encoding ion channels. This can only account for a minority of cases, however. Our recent work on a novel mouse model of SIDS suggests a potentially more widespread role for cardiac arrhythmia in SIDS without needing to invoke the inheritance of abnormal ion-channel genes. We propose a model for SIDS pathogenesis whereby postnatal hypoxia leads to delayed maturation of the cardiac conduction system and an increased risk of cardiac arrhythmia. Our model may integrate several epidemiological findings related to risks factors for SIDS, and agrees with previous work suggesting a common final pathological pathway in SIDS.

Sudden death of an infant with cardiac, nervous system and genetic involvement--a case report

Abstract

We present a case of sudden death of a 1-month-old male infant with heart, brainstem and genetic polymorphism involvement. Previously considered quite healthy, the child died suddenly and unexpectedly during sleep. The autopsy protocol included an in-depth anatomopathological examination of both the autonomic nervous system and the cardiac conduction system, and molecular analysis of the serotonin transporter gene promoter region, in which a specific genetic condition seems to be associated with sudden infant death. Histological examination revealed the presence of congenital cardiac alterations (hypertrophic cardiomyopathy and an accessory Mahaim fiber in the cardiac conduction system), severe hypodevelopment of all the raphe nuclei and a heterozygous genotype L/S related to the serotonin transporter gene. The sudden death of this infant was the unavoidable outcome of a complex series of congenital anomalies, each predisposing to SIDS.

Virtual slides

The virtual slide(s) for this article can be found here: http://www.diagnosticpathology.diagnomx.eu/vs/3480540091031788

Primary Cardiac Fibroma and Cardiac Conduction System Alterations in a Case of Sudden Death of a 4-month-old Infant

A 4-month-old female infant considered to be in good health died suddenly and unexpectedly. Post- mortem examination was requested, with clinical diagnosis of sudden infant death syndrome. At autopsy the infant was described in good health. Histo- logical examination of the heart found a cardiac fibroma compressing the atrio-ventricular node and the examination of the cardiac conduction system showed an accessory fiber of Mahaim (nodo-ventricular) and cartilaginous metaplasia of the cardiac fibrous body. Probably the concomitant presence of cardiac conduction system abnormalities and a septal fibroma, compressing the atrio-ventricular node, could have an important role in causing the sudden death.

Fetal and offspring arrhythmia following exposure to nicotine during pregnancy

Although recent studies have demonstrated prenatal nicotine can increase cardiovascular risk in the offspring, it is unknown whether exposure to nicotine during pregnancy also may be a risk for development of arrhythmia in the offspring. In addition, in previous studies of fetal arrhythmia affected by smoking, only two patterns, bradycardia and tachycardia, were observed. The present study examined acute effects of maternal nicotine on the fetal arrhythmia in utero, and chronic influence on offspring arrhythmia at adult stage following prenatal exposure to nicotine. Nicotine was administered to pregnant ewes and rats. In the fetal sheep, intravenous nicotine not only induced changes of fetal heart rate, but also caused cardiac cycle irregularity, single and multiple dropped cardiac cycles. Although maternal nicotine had no influence on fetal blood pH, lactic acid, hemocrit, Na(+), K(+) levels and plasma osmolality, fetal blood PO(2) levels were significantly decreased following maternal nicotine in ewes. In offspring rats at 4-5 months after birth, prenatal exposure to nicotine significantly increased heart rate and premature ventricular contraction in restraint stress. In addition, arrhythmias induced by injection of nicotine were higher in the offspring prenatal exposure to nicotine in utero. The results provide new evidence that exposure to nicotine in pregnancy can cause fetal arrhythmia in various patterns besides tachycardia and bradycardia, the possible mechanisms for nicotine-induced fetal arrhythmia included in utero hypoxia. Importantly, following exposure to nicotine significantly increased risk of arrhythmia in the adult offspring. The finding offers new insight for development of cardiac rhythm problems in fetal origins.

Neuropathology of the intermediolateral nucleus of the spinal cord in sudden unexplained perinatal and infant death

Experimental studies have demonstrated that breathing activity in rats is generated early in embryonic stages in rostral spinal cord, precisely in the intermediolateral nucleus, then establishing a spinal cord-brainstem network. In this study we aimed to individuate and to define the developmental steps of the intermediolateral nucleus, still inadequately known in humans, in the thoracic spinal cord of a large series of perinatal and infant death victims, aged from 17 gestational weeks to 10 months of life. Besides we investigated a possible link between alterations of this nucleus and sudden unexplained perinatal and infant death. The normal developmental pattern of the human intermediolateral nucleus consists of a progressive maturation of its neurons, that change from a round to a polygonal shape with long axons and significantly decrease in number. Various degrees of intermediolateral nucleus hypodevelopment (neuronal immaturity in a normal structure/hypoplasia/agenesis) were found almost exclusively in unexplained fetal and infant death victims. Besides, a significant correlation was found between maternal smoking in pregnancy and the neuropathological results. In conclusion this work underlines the negative effects of prenatal nicotine exposure on the development of autonomic nervous centers checking the vital functions, already in early gestational stages, when the integrity of the intermediolateral nucleus is indispensable for the first breathing bursts.

Sudden infant death syndrome "gray zone" disclosed only by a study of the brain stem on serial sections

Sudden infant death syndrome (SIDS) "gray zone" or borderline cases are defined as those cases in which it is difficult to establish whether the pathological findings are sufficiently severe to have caused the death. Examination of the brainstem in 103 cases of SIDS disclosed five SIDS "gray zone" cases in which only further investigations of serial sections successfully identified anatomico-pathological findings that likely represent the morphological substrates for a sudden reflexogenic death. A complete autopsy was performed, including close examination of the brainstem and cardiac conduction system, according to our guidelines. Our five cases are consistent with the triple-risk model of SIDS, a hypothesis postulating an underlying biological vulnerability to exogenous stressors or triggering factors in a critical developmental period. Inflammatory infiltrates (cases 1 and 2), necrotic focus of the solitary tract (case 3), hemangioendothelioma (case 4) and mild pneumonia (case 5) alone might or might not have accounted for the sudden deaths, if it had not been for the location and/or concomitant presence of brainstem abnormalities that could have had a triggering role in causing the sudden death of these babies.

Early atherosclerotic lesions of the cardiac conduction system arteries in infants

INTRODUCTION

Although several studies have described initial atherosclerotic lesions of the coronary arteries, already detectable in infancy and even during the intrauterine life, little, if any, attention has been given to the possible involvement of the cardiac conduction system arteries. In particular, to the best of our knowledge, none has considered the lesions of the cardiac conduction arteries as an initial stage of atherosclerosis.

METHODS

The cardiac conduction system of 70 infants dying suddenly and unexpectedly was removed in two blocks for paraffin embedding and serially cut.

RESULTS

The histological study of the cardiac conduction arteries of the 70 cases examined showed a normal structure in 55 cases (78.57%). In 15 cases (21.43%), there was a thickening of the sinoatrial node and/or atrioventricular artery associated with a thickening of varying severity in coronary artery walls. The lesions were marked by thickening and deposits of amorphous material and mainly lipids in the intima, as well as fragmentation of the elastic fiber system. A significant correlation was evident between early atherosclerotic lesions and both formula feeding and parental cigarette smoking (P<.05, chi(2) test).

CONCLUSIONS

The combination of both the considered risk factors seems to increase the early atherogenic effect of each noxa because the coronary lesions were more diffused in formula-fed infants whose parents both smoked.

Study of the brainstem, particularly the arcuate nucleus, in sudden infant death syndrome (SIDS) and sudden intrauterine unexplained death (SIUD)

Complete examination of the brainstem involves transverse serial 5-microm sections made throughout the entire brainstem. The number of serial sections varies from 360 in sudden intrauterine unexplained death (SIUD) to 600 in term fetuses to over 1400 sections in sudden infant death syndrome (SIDS) victims. The procedure is not applicable in all histopathological laboratories, owing to the need for additional technical personnel. The simplified procedure allows a remarkable reduction of the number of sections. The brainstem is divided into 3 blocks. The first, cranial block, extends from the border between the medulla oblongata and pons up to the upper pole of the olivary nucleus. The second, intermediate block, corresponding to the submedian area of the inferior olivary nucleus, has as reference point the obex and extends 2 to 3 mm above and below the obex itself. The third, caudal block, includes the lower pole of the inferior olivary nucleus and the lower adjacent area of the medulla oblongata. Examinations of the brainstems from 106 SIDS victims, 30 controls, and 51 stillborns underlined a remarkable variability, particularly of the arcuate nucleus. The simplified examination of the brainstem makes it possible to evaluate the structures, examining 3 specific levels, defined by morphologic reference points.

Crib death: further support for the concept of fatal cardiac electrical instability as the final common pathway

This work intends to be a review of the current status of knowledge on the cardiac conduction system in the crib death as well as remaining challenges, including reflections upon authors' personal works as well as many studies by others. The cardiac conduction system findings of resorptive degeneration, His bundle dispersion, Mahaim fibers, cartilaginous meta-hyperplasia, persistent fetal dispersion, left sided His bundle, hemorrhage of the atrio-ventricular junction, septation of the bifurcation, atrio-ventricular node dispersion, sinus node hypoplasia, Zahn node, His bundle hypoplasia, atrio-ventricular node and His bundle dualism are hereby discussed by the authors. The cardiac hypotheses postulating that crib death could be due to lethal cardiac arrhythmias or heart block were considered of great interest in the 1970s. After a general abandon of the conduction studies in crib death, the cardiac concept of crib death is gathering a renewed interest, as well as the occurrence of infantile junctional tachycardia. Both the morphological and functional derangement underlying crib death remain poorly understood, assuring that it remains to be a major medical and social problem. Despite the non-specificity of most of the cardiac conduction findings in crib death, we believe that they, in association with altered neurovegetative stimuli, could underlie potentially malignant arrhythmias, providing a morphologic support for the cardiac concept of crib death.

Sudden death due to lymphomatous infiltration of the cardiac conduction system

We present the case of a 62-year-old white female with a history of previously treated angioimmunoblastic T-cell lymphoma, who died suddenly 1 day after presentation for presumed tumor recurrence. Postmortem gross examination revealed a 4-cm cardiac mass that was adherent to the free wall of the right atrium. Histologic examination showed extensive infiltration of the cardiac conduction system by lymphoma, which likely lead to fatal arrhythmia. Histological examination revealed systemic dissemination by an Epstein-Barr virus (EBV)-positive large B-cell lymphoma. Careful examination of the cardiac conduction system on serial sections was crucial in documenting the cause of death due to lymphomatous infiltration. As in this patient, lymphomatous infiltration of the heart may produce sudden cardiac death without obvious premortem signs of cardiac compromise. This case illustrates the utility of examination of the cardiac conduction system in necroscopy studies of sudden death.

Cardiac pathology in sudden unexpected infant death

OBJECTIVES

To determine the spectrum of cardiac pathology and circumstances of death in infants with sudden unexpected death and to define the impact of sudden cardiac deaths to overall sudden infant death.

STUDY DESIGN

Retrospective analysis of all autopsies of infants with sudden death 7 days to 2 years of age between January 1987 and December 1999 in the province of Québec (Canada).

RESULTS

Eighty-two cases of sudden death with cardiac pathology were found, representing 10% of the total number of sudden infant deaths. A structural malformation was present in the majority of cases (54%); however, cardiac pathology in anatomically normal hearts was also common (46%). Most (64%) anatomic malformations were detected before death compared with 13% of nonstructural heart disease. Although a major proportion of children were found dead during sleep, a significant number were described as being awake at time of death (32%).

CONCLUSIONS

Heart disease is present in a significant percentage of autopsies of infants with sudden death. Structural heart malformations predominate, although nonstructural pathologic features of the heart are common and usually unrecognized before an autopsy is performed. Cardiac pathologic features are frequent when the child is witnessed to be awake at the time of sudden death.

A serotonin malfunction hypothesis by finding clear mutual relationships between several risk factors and symptoms associated with sudden infant death syndrome

In our recent study allele variants in the promoter of serotonin transporter (5-HTT) gene have been shown as a novel risk factor for sudden infant death syndrome (SIDS). L and XL alleles were more frequent and S allele was less frequent in SIDS victims compared to age-matched controls. Serotonin (5-HT) is suggested as a major agent that is closely involved in the etiology of SIDS. Although many risk factors of SIDS looked mutually unrelated each other, we found in literature many of them other than prone position to change 5-HT levels in the brain. Along with the genetic factors, environmental and temporal factors appear additively to lower the excitatory function of 5-HT to the respiratory center, and finally SIDS might occur. Now the pathophysiological mechanisms and symptoms of SIDS are explained by decreased levels of 5-HT.