PMC9749817_01
Echocardiographic apical 4-chamber view (A-C), parasternal long axis (D,E) and MRI (F) imaging before EFE resection. 2D (A,D) and 3D (B,C,E) echocardiography showing hyperechogenic thickening of the endocardium on atrial, mitral valve, LV and LVOT level consistent with generalized EFE in the left sided structures of the heart is shown. Severe dilation of the left atrium can be noted. (C) Severe turbulences are detected by color Doppler in all left sided structures affected by EFE as compared to physiological color Doppler appearance in the right sided structures of the heart that are not affected by EFE. (F) Late gadolinium enhancement on endocardial level encapsulating all structures of the left atrium and ventricle is depicted.
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F1
MV and subaortic region. Marked thickening of the atrial surfaces of the anterior and posterior MV leaflets in the mid leaflet region prevented effective leaflet coaptation (Figure 1).
Representative histological evaluation of resected EFE tissue. Organized structured avascular collagen and elastin matrix with scarce cellularity, consistent with the histological picture of EFE is shown (A) H&E staining shows only sparse mononuclear likely mesenchymal stromal cells (B). Masson's trichome stain displays a thickened subendocardium with multiple and often alternating layers of elastic fibers (red wavy profiles) and fibrous tissue (blue) with extension into the subjacent myocardium. (C) Double-staining of endocardial endothelial cells with VE-cadherin (red) and alpha-smooth muscle actin (green) were performed to detect EndMT. A representative section is shown. The majority of endocardial endothelial cells express both markers at the same time, indicating active EndMT. (D) Lack of predominant inflammatory invasion of EFE tissue is confirmed by negative immunofluorescence staining for CD45 (absence of green). Cardiomyocytes are counterstained with Troponin I (red).
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F2
Additionally, immunofluorescence analysis of the resected EFE tissue from all areas showed a high number of cells expressing both endothelial and mesenchymal markers, indicative of active EndMT (Figure 2).