PMC10050595_01
At initial presentation: a dilated right atrium was noted in apical four-chamber view (A); chest radiography showed cardiomegaly with a CTR of 80% (B); electrocardiograph showed sinus tachycardia, right axis deviation, and incomplete right bundle branch block (C). After surgical reduction, a slightly enlarged right atrium and intact atrial septum (D), CTR decreased to 0.61 (E), and the atrial premature beat was detected (F). CTR, cardiothoracic ratio;
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F1
Transthoracic echocardiogram (TTE) showed a giant RA (50 mm x 48 mm) with normal right and left ventricular volumes, a 15 mm secundum atrial septal defect (ASD), the tricuspid annulus was 14 mm, slight tricuspid regurgitation, a pulmonary arterial systolic pressure (PASP) of 45 mmHg, and left ventricular ejection fraction (LVEF) of 65% (Figure 1A). The chest x-ray showed an enlarged heart, and the cardiothoracic ratio (CTR) reached about 0.80 (Figure 1B). Electrocardiograph showed sinus tachycardia, right axis deviation, and right bundle branch block (Figure 1C). Repeat TTE showed a slightly enlarged RA, intact atrial septum, and normal LVEF (Figure 1D). Chest x-ray revealed a decreased CTR as 0.61 (Figure 1E).
H&E staining showing the pathological changes in myocardial tissues of the right atrium (A), right ventricle (B), and left atrium (C). TEM shows damage to myofibrils and mitochondria in the right atrium (D), right ventricle (E), and left atrium (F). Scar bar: 1 microm. Magnification: x25,000 and x20,000. TEM, transmission electron microscopy.
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F2
ASD. Resection of extensive RA wall and atrioseptopexy were performed. At surgery, biopsies of the RA wall, right ventricle (RV) and left atrium (LA) revealed unspecific inflammatory cell infiltration and various degrees of focal myocardial hypertrophy and degeneration (Figures 2A-2C). Transmission electron microscopy (TEM) demonstrated damage to myofibrils and mitochondria, with a blurring of mitochondrial cristae (Figures 2D-2F).
Changes in echocardiogram with follow-up time: parasternal long axis view indicated left ventricular end-diastolic dimension increased within 1, 2, and 5 years (A,C,E); apical four-chamber view showed an enlarged right atrium, the changes were not significant within 1, 2, and 5 years (B,D,F).
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F3
At 1-year follow-up, there was a progressive enlargement of the RA (Figures 3A,B), and the patient remained asymptomatic except for growth retardation. Unexpectedly, TTE 2 years after epilepsy surgery demonstrated an enlarged left ventricle (LV) with a left ventricular end-diastolic diameter (LVEDD) of 40 mm, a giant RA (52 mm x 39 mm), a normal PASP of 20 mmHg, and reduced LVEF of 55% (Figures 3C,D). The size of the RA and LV did not change significantly, and the LVEF was about 50% (Figures 3E,F).
Cardiac magnetic resonance showed an enlarged right atrium, left atrium, and left ventricle; no typical manifestations of ventricular myocardial fibrosis were detected. RA, right atrium; LA, left atrium; RV, right ventricle; LV, left ventricle.
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F4
Cardiac magnetic resonance (CMR) showed cardiomegaly at the expense of the right atrium with a decreased LVEF of 45% and no typical manifestations of ventricular myocardial fibrosis (Figure 4).