"Salvage the pacemaker" at autopsy

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.

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.

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

The theory that Sudden Infant Death Syndrome (SIDS) may be related to lethal cardiac arrhythmias or heart block due to structural abnormalities of the conduction system is attractive and still of particular interest. We analyze 69 autopsied cases of SIDS (46 males and 23 females, infants ranging in age from 3 to 365 days) and 24 age-matched cases of explained death (ED) as controls (16 males and 8 females), infants who died from extracardiac cause (cerebral and respiratory). SIDS and ED groups were divided into three subgroups according to the age: (A) from 3 to 60 days; (B) from 61 to 120 days; (C) from 121 to 365 days. Histological observations were focused on the cardiac conduction system (CCS) which was examined on serial sections with the technique devised by one of the present authors (L. Rossi). The following findings were observed: resorptive degeneration (97.10% of SIDS, 75% of ED), His bundle dispersion (33. 33% of SIDS, 16.66% of ED), Mahaim fibers (21.73% of SIDS, 8.3% of ED), cartilaginous meta-hyperplasia (5.79% of SIDS, 4.16% of ED), persistent fetal dispersion (24.63% of SIDS, 16.66% of ED), intramural right bundle (20.29% of SIDS, 25% of ED), left sided His bundle (20.29% of SIDS and 8.3% of ED), hemorrhage of the atrio-ventricular junction (15.94% of SIDS), septation of the bifurcation (13.04% of SIDS), atrio-ventricular node (AVN) dispersion (7.24% of SIDS), sino-atrial node hypoplasia (5.79% of SIDS), Zahn node (1.45% of SIDS), His bundle hypoplasia (1.45% of SIDS), intramural left bundle (1.45% of SIDS), AVN dualism (2.89% of SIDS), and His bundle dualism (2.89% of SIDS, 4.16% of ED). Only the presence of resorptive degeneration was significantly higher in SIDS than in ED cases (p = 0.004). Regarding the subgroups, the only significant difference was the higher presence of intramural right bundle in SIDS-A than in SIDS-B (p = 0.01). Despite the non-specificity of most of these findings, we believe that these changes, associated with particular conditions and/or neurovegetative stimuli, could cause potentially malignant arrhythmias. These data suggest the need for an accurate approach and examination of the cardiac conduction system in all cases of sudden death in infancy