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The endocardium defines the inner soft tissue lining of the heart within the cardiac chambers and constitutes the superficial surface of the cardiac valves. It apparently serves as a regulatory mechanism on myocardial contractility.
The endocardium represents the inner layer of the cardiac wall and covers the inner surface of the cardiac chambers and the superficial surface of the cardiac valves. It consists of endothelial cells, connective tissue, elastic fibers and smooth muscle cells and contains nerve fibers 1-3.
The adjacent subendocardial connective tissue layer contains the Purkinje fibers transmitting electric signals to the myocardium 1-3.
The ventricular endocardium consists of different layers 1-3:
- consists of endothelial cells (squamous epithelial cells)
- the subendothelial connective tissue layer
- contains collagen fibrils and fibroblasts
- more prominent in the atria, in particular, the left atrium
- elastic tissue layer
- contains elastic fibers, collagen fibers and smooth muscle cells
- more prominent in the left atrium and the left ventricular septum
- subendocardial tissue layer
- connects endocardium to the myocardium
- contains collagen and elastic fibers, small blood vessels and Purkinje fibers
- merges with the extracellular matrix of the myocardium
Due to its thin layer, the normal endocardium is not visualized on imaging.
However, it might be depicted if thickened or altered in the setting of disease.
Ultrasound is the first-line modality in the evaluation of valvular heart disease.
Irregularities and in particular vegetations suggest endocardial disease.
The healthy endocardium will not be visible. However cardiac MRI might aid in the diagnosis of pathologically altered endocardium.
An apical filling defect and/or diffuse late gadolinium enhancement of the endocardium in particular if several chambers are involved will suggest endocardial disease e.g. endomyocardial fibrosis or endocardial fibroelastosis 5-7.
The following pathologies and diseases are related to the endocardium 5-7:
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