Heart block due to epithelial heterotopia

Cystic tumour of the atrioventricular node: case report and literature review

Cystic tumour of the atrioventricular node is the smallest tumour that can cause sudden cardiac death. This lesion arises from foregut endodermal rests which become enfolded into the heart during embryogenesis. Typically causing heart block, the tumour can cause sudden death despite pacemaker placement. Sudden death in such cases can be caused by arrhythmogenic ectopic foci arising from impaired electrical impulse propagation through the abnormal atrioventricular junction conducting tissue.

Epithelial cyst of the cardiac papillary muscle: case report and review of the literature

BACKGROUND

Reports of endodermal heterotopia (previously known as inclusion cysts) in cardiac atria are rare and there is only a single previous case report of endodermal heterotopia in a cardiac papillary muscle.

AIM AND METHODS

A cyst in a cardiac papillary muscle was identified during the autopsy of an 87-year-old man who had died from an unrelated myocardial infarction. The cyst was examined histologically and mucin staining and immunostaining were carried out.

RESULTS

We report a unilocular cyst in a cardiac papillary muscle, which is lined by low cuboidal, pseudostratified and occasionally ciliated respiratory-type epithelium, surrounded by a layer of smooth muscle. The immunohistochemical features (MNF116+, cytokeratin (CK)7+, CK8+, CK18+, CK19+, epithelial membrane antigen positive, scattered cells positive for neuroendocrine markers) suggest that this is an endodermal heterotopia. Immunostaining of positive thyroid transcription factor-1 provides evidence for bronchogenic differentiation.

DISCUSSION

The differential diagnoses of cystic structures in cardiac papillary muscle and the origin and importance of endodermal heterotopias are discussed.

Mesothelioma of the AV node: potential utility of pacing

Mesothelioma of the atrioventricular node are rare benign tumors with well-described potential for resulting in sudden death. The presentations have varied: the majority of patients have been predominantly female aged 15 to 40, dying suddenly; however, other patients have had documented heart block for many decades and a noncardiac cause of death. A 19-year-old female expired after presenting with ventricular fibrillation and was subsequently discovered to have a mesothelioma involving the AV node. Although high degree heart block is present in many patients, most episodes of sudden death probably are secondary to ventricular tachyarrhythmias. Either form of dysrhythmia may potentially benefit from ventricular pacing.

Mesothelioma of the atrioventricular node

A patient with Mobitz type 2 heart block caused by a mesothelioma of the atrioventricular node died of a subarachnoid haemorrhage at the age of 33 two years after implantation of a permanent pacemaker. Mesothelioma of the atrioventricular node is rare, and reported cases have all been diagnosed post mortem. Mesothelioma of the atrioventricular node should be considered in the differential diagnosis of heart block in children or young adults. This is the first case to be reported in Japan.

Mesothelioma of the AV node

A 21-month-old boy died suddenly six months after presenting with heart murmur and second-degree atrioventricular (AV) block. Autopsy revealed a mesothelioma completely replacing the AV node and extending into the central fibrous body. The bundle of His and bundle branches were not involved. Mesothelioma of the AV node is a rare cause of supra-His (AV) block, arrhythmias, and sudden death.

Congenital polycystic tumor of the atrioventricular node: possible familial occurrence and critical review of reported cases with special emphasis on histogenesis

Congenital polycystic tumor of the atrioventricular node is a rare tumor of disputed histogenesis. It constant location in the atrioventricular node separates it from other cardiac cysts and tumors of indisputable endodermal origin. New studies of the embryogenesis of conduction tissues provide a reasonable explanation for the site of the lesion. Morphologic and histochemical features of the tumor fail to conclusively favor either a mesothelial or an endodermal genesis. A recently studied case provides some new morphologic observations (complex desmosomes, granule-containing epithelial cells) and suggests the possibility of of familial occurrence.

Atrioventricular block in childhood caused by mesothelioma

The case of a girl who was first seen at 3.5 years of age with longstanding asymptomatic heart block is reported. Electrophysiological study disclosed a block proximal to the His bundle. She grew up normally until the age of 11.5 years, when a syncopal attack occurred. Before a pacemaker could be inserted, she suffered a second fatal attack. Necropsy revealed a tumor of the atrioventricular node diagnosed as mesothelioma. Our findings are compared to the 38 cases already described in the literature.

Sudden unexpected cardiac death--a practical approach to the forensic problem

Sudden cardiac death can usually be resolved by the pathologist into ischaemic heart disease, non-vascular cardiac disease such as aortic stenosis or hypertrophic obstructive cardiomyopathy and infrequently a morphologically normal heart on naked eye examination. When ischaemic heart disease is present one third of cases have a recent occlusive coronary artery thrombosis. Two thirds of patients have coronary stenosis only; the minimum degree of disease reasonably associated with sudden death is one area of 85% stenosis. The majority of patients, however, have multiple areas of stenosis. The predominant causes of non-ischaemic sudden death are severe LV hypertrophy, hypertrophic obstructive cardiomyopathy and the prolapsing mitral valve syndrome. Where the heart and coronary arteries are morphologically normal, review of any previous ECG's, a family history and histological examination of the myocardium and conduction system may reveal a cause or at least allow a reasonable assumption of cardiac arrhythmia to be made. Sudden unexpected death where the circumstances strongly suggest a cardiac cause may pose problems for the pathologist. Ischaemic heart disease (coronary atherosclerosis) is undoubtedly the most frequent cause but even when this is so the detailed pathology is controversial. It is when coronary artery disease is conspicuously absent, often in young individuals previously in good health, that a problem exists. Sudden death in infancy (cot death) is a different entity with its own problems and is not here discussed further.

Intracardiac heterotopia--mesenchymal and endodermal

A case is reported of an intracardiac 'epithelial heterotopia' with a predominant mesenchymal component. This is thought to have resulted from the differentiation of aberrant primitive cell(s) displaced into the heart during its development. Though microscopically resembling a myxoma, this lesion is clearly distinguished by the presence of glandular structures. The myxoid component exhibited a startling invasiveness which resulted in occlusion of the superior vena cava, causing symptoms very early in life and death at the age of 6 months.

Corpora amylacea in mesothelioma of the atrioventricular node

Rounded or polyhedral, acellular, dense lamellated structures were seen within gland-like spaces in a case of atrioventricular mesothelioma. These structures exhibited many of the histochemical characteristics of amyloid, viz., pink colour with green birefringence and bright red fluorescence with alkaline Congo red; ortochromasia and red birefringence with standardised toluidine blue; positive DMAB-nitrite and diazotisation coupling reactions and spontaneous autofluorescence. It is suggested that these bodies are derived from spontaneous assembly or polymerisation of microfibrils of desquamated cells lining the cystic spaces of the tumour as occurs in prostatic corpora amylacea. The peculiar intramyofibre proliferation of tumour cells in the peripheral part of the tumour suggests that viable tumour cells can penetrate, survive and proliferate within atrial or nodal myofibres leaving an intact sarcolemmal sheath. The slow tumour cell growth and the successive degeneration of central tumour cells may explain the tubular and/or glandular pattern constantly seen in this tumour.

De subitaneis mortibus. XXVI. Fatal electrical instabiltiy of the heart associated with benign congenital polycystic tumor of the atrioventricular node

Benign congenital polycystic tumors of the atrioventricular (A-V) node are an unusual but not very rare cause of heart block. Two such cases are presented and discussed in conjunction with the reported experience of other. The tumor is always within and only very near the A-V node, seldom involves more than the proximal end of the His bundle, and has not been reported to occur in the sinus node. Although sudden death has been reported in conjunction with these tumors, a surprising number of other patients have lived to old age and died of causes unrelated to the A-V nodal tumor. As a corollary it is important to consider a diagnosis of A-V nodal tumor in any patient of any age who presents with otherwise unexplained heart block or syncope. From accumulated experience it appears that such patients do not tolerate electronic pacing safely and some possible explanations for this are discussed. Escape rhythm in all reported cases has been characterized by QRS complexes which are narrow and a ventricular rate which is from half to two-thirds of the sinus rate. Reasons why an A-V junctional rhythm which is 66% of sinus rate may be especially stable are discussed.