Pathobiology of sudden death: coronary causes

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 death of a child from myocardial infarction due to arteritis of the left coronary trunk

An eight-year-old Japanese boy developed abdominal pain, followed by convulsion and loss of consciousness. He was taken to an emergency room but could not be resuscitated. At autopsy, the left main coronary trunk (LMT) demonstrated an increase in caliber with severe luminal narrowing, and the left anterior descending branch (LAD) subsequent to the LMT showed severe stenosis. Microscopically, the intima of the LMT demonstrated severe fibrosis and infiltration of lymphocytes and histiocytes suggesting vasculitis, and the small lumen was occupied by a fresh thrombus. The LAD showed significant intimal thickening with strong lymphocytic inflammation at the edge of the thickening. The left ventricle showed widespread myocardial infarction in the recovery stage. There were no findings of atherosclerosis, vasculitis or fibrocellular changes in the ascending aorta or intravisceral arteries other than the LMT and the LAD under investigation. The increase in the caliber of the LMT and the limitation of arteritis to the LMT and the subsequent branch suggested Kawasaki disease (KD), but it was atypical that the patient had no clinical history consistent with KD. The present case showed no findings suggesting classical polyarteritis nodosa (cPAN) at the acute or scar stage in the other vessels being investigated, and cPAN in childhood is rare compared to KD. A nonspecific inflammatory reaction (single organ vasculitis, SOV) was also considered as a possible cause, but it is difficult to determine whether the cause of the coronary stenosis in the present case was SOV because the sampling of arteries was insufficient. If forensic pathologists make unusual findings suggesting vasculitis at autopsy, the collection of a sufficient number of vessels of various sizes is warranted.

[Sudden death caused by atheromatous coronary disease in the young]

INTRODUCTION AND OBJECTIVES

Atheromatous coronary disease (ACD) is the most frequent cause of sudden death (SD) in adults. Few studies have focused in SD due to ACD in those patients under 35 years old. The aim of this study is to analyze the incidence, and clinical and pathological characteristics of ACD as a cause of death in young people.

MATERIAL AND METHODS

We reviewed all SD cases in people from 1-35 years old which occurred in Bizkaia and in which there was a legal-medical autopsy from 1991 to 1998. A complete autopsy was performed in each case. SD due to ACD were analyzed, including pathological antecedents.

RESULTS

19 out of 107 SD (18%) occurred by ACD. All of them were males from 27 to 35 years of age. According to the male population from 30 to 35 years, the incidence was 3.7/100,000/year. In two patients ACD was diagnosed before death. Coronary risk factors were obtained in 10 cases and prodromal symptoms were described in 5 (chest pain in 4). In 79% death occurred during routine activity. None of the 19 patients arrived alive to hospital. In 6 cases multiple coronary disease was observed; coronary thrombosis in 8; recent acute ischemic myocardial necrosis in 4 and old ischemic damage in 7. 18 cases showed cardiac hypertrophy.

CONCLUSIONS

ACD is an important cause of SD in young males, frequently being the first manifestation of the disease. As identification of groups at risk is so difficult and death occurs so quickly, primary prevention of ACD, rapid intervention of emergency services and educational programs in cardiopulmonar resuscitation for normal population are fundamental in reducing the mortality.

Atrioventricular node fetal dispersion and His bundle fragmentation of the cardiac conduction system in sudden cardiac death

OBJECTIVES

This study sought to examine the frequency of persistent fetal dispersion of the atrioventricular (AV) node and fragmentation of the atrioventricular bundle (His) bundle in the cardiac conduction system of sudden cardiac death cases and control subjects to establish their importance as the cause of death.

BACKGROUND

These are two of the most frequent lesions reported in published reports in the cardiac conduction system in unexplained sudden deaths.

METHODS

We have studied the conduction system of 347 hearts: 249 hearts from sudden cardiac death cases and 98 control hearts. The sudden cardiac death cases were divided, according to the pathology found, in three groups: group I: ischemic heart disease, 137 cases; group II: nonischemic heart disease, 48 cases, and group III: unexplained sudden cardiac deaths, 64 cases. The control group (group IV) consisted of patients with unnatural deaths and extracardiac natural deaths.

RESULTS

Persistent fetal dispersion of the AV node was observed in 70 cases (20.17%) of all groups with a frequency (40.81%) statistically higher in the control group. Fragmentation of the His bundle was observed in 95 cases (31.77%), and the frequency was statistically higher in the control group, too (47.67%).

CONCLUSIONS

Persistent fetal dispersion of the AV node and fragmentation of the His bundle can be a normal variation present during many years in life and must not be considered the anatomic substrate for arrhythmias and sudden death without electrocardiographic abnormalities.

Mast cell distribution, activation, and phenotype in atherosclerotic lesions of human carotid arteries

Immunohistochemical staining for mast cell tryptase and chymase was used to examine the distribution, activation, and tryptase/chymase phenotype of mast cells (MCs) in 250 samples of atherosclerotic lesions (type I to VI) of human carotid arteries. Dual immunolocalization and histochemical techniques were used to identify the associations of MCs with macrophages, smooth muscle cells, and extracellular matrix components. Whereas normal carotid arteries contained very few MCs within the intima, atherosclerotic lesions showed increased MC numbers with variable focal accumulations. MCs were identifiable from the earliest stages of atherosclerosis, and especially at the shoulder regions of the fully formed atheroma. They were observed in close association with macrophages (HAM56 positive) and extracellular lipid, as well as at sites of foam cell formation. MCs and diffuse tryptase staining were also evident within sites of new calcification and around small calcified deposits. Extensive MC activation/degranulation, as judged by diffuse extracellular tryptase staining, was a common feature of the advanced atherosclerotic plaques complicated by fissure, haemorrhage, and thrombus formation. Moreover, such sites of extracellular MC tryptase were often associated with localized oedema and disruption of the stromal matrix. MCs which contained both tryptase and chymase (the MCTC phenotype) represented approximately 80-95 per cent of all MCs. These studies are the first to demonstrate significant numbers and focal accumulations of MCs in all developmental stages of atherosclerotic carotid arteries. Since MCs contain or express a variety of potent mediators, their release could profoundly influence the development and pathological complications of atherosclerotic plaques.

Biochemical markers of myocardial damage

OBJECTIVE

To assess various biochemical markers of myocardial damage.

METHODS AND RESULTS

Before routinely using any test as a biochemical marker of myocardial damage, the published evidence for its diagnostic utility must be critically assessed. Such assessment includes receiver operator curve (ROC) curve analyses, confidence interval estimates of claimed sensitivity and specificity values, and the effects of testing in serial and parallel modes. It is also necessary to establish the test's rule-in (high specificity) and rule-out (high sensitivity) decision thresholds that may vary with time after the onset of symptoms. The spectrum of ischemic heart disease includes acute (sudden death, non-Q- and Q-wave infarctions) and chronic (stable, unstable, and variant angina) conditions. Biochemical markers of myocardial damage are of most value in the diagnosis of acute ischemic heart disease, although increasingly some of these markers are being found to possess a prognostic value in chronic ischemic heart disease. The markers of enzymatic activity include aspartate aminotransferase, creatine kinase (together with isoenzymes and isoforms), and lactate dehydrogenase and isoenzymes. Creatine kinase isoenzyme-2 may also be measured immunologically, and this type of assay is in increasing use both because of its speed and because its blood levels rise earlier than the corresponding activities. The commercially available nonenzymatic markers are myoglobin and troponin T; troponin I is expected to become available in late 1995. While myoglobin is a nonspecific indicator of myocardial damage, its diagnostic value is due to its early appearance in blood. Troponin T is more cardiac specific, but the published data appears to suggest that the cardiac specificity of troponin I is superior. Troponin levels become abnormal at about the same time after the onset of symptoms as mass assays of creatine kinase isoenzyme-2; therefore, they are not useful as early markers of myocardial damage.

CONCLUSION

The availability of these nonenzymatic markers of myocardial damage must force a reassessment of the continued use of the enzymatic markers. Are they necessary, and if so, which ones should be retained?