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Electron microscopical study of myocardial biopsy material in congenital heart block
Insights
Congenital atrioventricular block in children may involve mitochondrial proliferation and unusual sarcolemmal structures. These ultrastructural changes in myocardial cells might impact cardiac impulse conduction.
Area of Science:
- Cardiology
- Cell Biology
- Pediatrics
Background:
- Congenital atrioventricular block is a serious condition often requiring pacemaker implantation.
- Understanding the underlying myocardial structure is crucial for managing conduction defects.
Purpose of the Study:
- To investigate the ultrastructural changes in myocardial tissue of children with congenital atrioventricular block.
- To explore potential cellular mechanisms contributing to conduction abnormalities.
Main Methods:
- Electron microscopy was used to examine myocardial tissue samples.
- Tissue was obtained from two pediatric patients during epicardial pacemaker implantation.
Main Results:
- Both patients showed mitochondrial proliferation.
- One patient with familial cardiomyopathy exhibited interstitial fibrosis and transverse tubule proliferation.
- The other patient displayed deep sarcolemmal invaginations forming intracytoplasmic channels.
Conclusions:
- Ultrastructural abnormalities, including mitochondrial proliferation and altered sarcolemmal structures, are present in pediatric congenital atrioventricular block.
- Transverse tubule proliferation may offer alternative pathways for cardiac impulse conduction.
Abstract:
Myocardial tissue from the left ventricle of two children with congenital atrioventricular block and recurrent Admas-Stokes attacks was obtained during the procedure of epicardial pacemaker implantation and studied with the electron microscope. One patient had a familial cardiomyopathy, the other had no clinical abnormality apart from the conduction defect. Proliferation of mitochondria was common in both cases. Focal interstitial fibrosis and pronounced proliferation of transverse tubules were found in the myocardial cells of the patient with familial cardiomyopathy. Deep invaginations of the sarcolemmma with formation of intracytoplasmic channels were present in the second case. The possibility that the numerous transverse tubules could serve as additional pathways for impulse conduction is discussed.