PMC8687144_01
(A) Functional cardiac MRI in short axis revealed a diastolic D-shaped left ventricle, indicating increased right ventricular pressure. (B,C) Cardiac MRI in short and long axis demonstrated a tissue defect in the inter-atrial septum (*). (D) Post mortem examination confirmed a large ASD (*). ASD was partially occluded by a serous cyst (arrow).
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F1
Functional MRI showed a clear defect in the atrial septum and a moderately enlarged right ventricle (Figures 1A-C). Moreover, end-diastolic D-shape of the left ventricle was observed, indicating right ventricular volume overload (Figure 1A). The autopsy of the heart revealed a defect in the atrial septum in which the atrioventricular orifices remained separate, but with a continuous AV valve bridging the septum, thus creating an ostium primum ASD (Figures 1D, 3B).
Overlay of cardiac functional MRI and pathline visualization of blood flow during the cardiac cycle. RA, right atrium; LA, left atrium; RV, right ventricle; LV, left ventricle. (A-C) Pathline visualization of blood flow originating from the left (red) and from the right (blue) atrium, showing left-to-right flow across the atrial septum during diastole (L-R shunt). (D) Velocity field visualization focused on the diastolic shunt across the atrial septum. (E-G) Pathline visualization of regurgitant blood flow through the closed mitral and tricuspid valve during systole. (H) Velocity field visualization focused on the systolic mitral and tricuspid regurgitant flow.
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F2
Peak velocities of mitral and tricuspid regurgitant jets were 36.4 and 46.9 cm/s, respectively, indicating a severe dysfunction of the atrioventricular (AV) valves (Figure 2).
(A) Left ventricular free wall and posterior mitral valve showing enlarged middle scallop (arrowhead). (B) Septum as viewed from the left ventricle showing ASD and cyst. The anterior mitral leaflet is exhibiting diffuse thickening (*), and A1/A2 clefting (arrow). (C) Right ventricular free wall and tricuspid valve with small nodular thickenings at the free margin (arrows).
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F3
The autopsy of the heart revealed a defect in the atrial septum in which the atrioventricular orifices remained separate, but with a continuous AV valve bridging the septum, thus creating an ostium primum ASD (Figures 1D, 3B). The mitral valve showed a large cleft in the anterior leaflet segment A1/A2, with A1 partially connected to the ventricular wall (Figure 3). The tricuspid valve also had several mild nodular thickenings at its free margin (Figure 3).
(A) Septum with ASD and protruding serous cyst as viewed from the right ventricle. (B) Low power (10x) histological overview of a longitudinal section through the interventricular septum including the cyst (*) which bridges the septum and atrioventricular valves; the left AV valve is to the right of the image, exhibiting marked thickening and distortion of the valve leaflet particularly at its tip. (C) FXIIIra/vWF staining shows positive staining of the outer aspect of the cyst wall, which corresponds to the endocardial valve surface, with negative staining of the inner (*) lining. (D) CD31 (pan-endothelial marker) staining shows positive staining of both aspects of the cyst wall. (E) Higher power view of the thickened valve tip of the mitral valve showing loss of layering of the leaflet and expansion of the spongiosa by whorls of stellate cells within a loose pale staining proteoglycan matrix (endocardiosis).
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F4
These findings indicate myxomatous valvular degeneration (endocardiosis) (Figure 4C). A serous cyst with a diameter of 1 cm protruded into and partially occluded the septal defect, extending from the septum at the exposed junction of the left and right AV valves (Figure 4A). Immunohistochemical staining of the cyst revealed a positive reaction of the cyst wall with CD31 and a negative reaction with FVIIIra, which corresponds to lymphatic origin and is compatible with the clear fluid contents of the cyst (Figure 4).