PMC9353184_01
Electrocardiography. (A) Electrocardiography upon admission showed Type I atrial flutter. (B) Post-operative electrocardiography (1st day) showed coronary sinus rhythm. (C) Post-operative electrocardiography (8th day) showed recovered sinus rhythm.
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Routine 12-lead electrocardiography displayed recurrent AFL at a ventricular rate of 112 beats/min (Figure 1A). The anomalous muscle bundles inferior to the infundibulum divided the RV into two cavities, inducing right ventricular outflow tract (RVOT) obstruction (Figures 2C,D and Supplementary Videos 1, 2). On the first postoperative day, the electrocardiography showed coronary sinus rhythm (Figure 1B). Sinus rhythm recovered on the 8th day after the operation (Figure 1C).
Echocardiography. Transthoracic echocardiography (A-F). (A) A 2-D apical four-chamber view with enlarged atria. (B) Left ventricular hypertrophy and interventricular septal hypertrophy. (C) Muscular septation within the right ventricle (the red arrow). (D) Flow acceleration showed by Color Doppler at the right ventricular outflow tract (the red arrow). (E) The systolic pressure gradient of the right ventricular outflow tract. (F) Ventricular septal defect (the red arrow) detected by Color Doppler. Transesophageal echocardiography (G,H). Color Doppler flow of the right ventricular outflow tract before (G) and after operation (H), as shown by the red arrows. LA, left atrium; RA, right atrium; LV, left ventricle; RV, right ventricle; Vel, velocity; PG, pressure gradient.
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Transthoracic echocardiography (TTE) revealed mildly reduced left ventricular ejection fraction (EF: 45%), mild pericardial effusion, biatrial enlargement (left atrium: 54 mm x 68 mm x 58 mm; right atrium: 59 mm x 43 mm) (Figure 2A), biventricular hypertrophy and asymmetrical interventricular septal hypertrophy (20 mm) (Figure 2B). The anomalous muscle bundles inferior to the infundibulum divided the RV into two cavities, inducing right ventricular outflow tract (RVOT) obstruction (Figures 2C,D and Supplementary Videos 1, 2). The peak pressure gradient of RVOT was approximately 44 mmHg, and the forward flow velocity was measured at 333 cm/s (Figure 2E). Furthermore, a small left to right membranous ventricular septal defect (VSD) (0.3 cm) shunt was discovered in the high-pressure chamber (Figure 2F and Supplementary Video 3). Intraoperative transesophageal echocardiography (TEE) demonstrated well-corrected RVOT (Figures 2G,H and Supplementary Videos 5-6).
Cardiac magnetic resonance. (A) A dumbbell-shaped right ventricle indicated right ventricular outflow tract obstruction (the red arrow). (B) A flow void sign at the right ventricular outflow tract (the red arrow). (C) No stenosis of infundibulum, pulmonary valve, and pulmonary artery. (D) Scattered patchy late gadolinium enhancement within the left ventricular myocardium (red arrows), particularly in the left ventricular anterior wall and the interventricular septum. (E,F) The native T1 mapping revealed the markedly increased T1 value at the basal interventricular septum from 1,123 to 1,260 ms. LA, left atrium; RA, right atrium; LV, left ventricle; RV, right ventricle; IVS, interventricular septum; PA, pulmonary artery; AO, aorta.
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Furthermore, a small left to right membranous ventricular septal defect (VSD) (0.3 cm) shunt was discovered in the high-pressure chamber (Figure 2F and Supplementary Video 3). A dumbbell-shaped RV and flow acceleration at the RVOT were observed during systole (Figures 3A,B and Supplementary Video 4). No signs of stenosis were identified in the infundibulum, PV, and pulmonary artery (PA) (Figure 3C). Scattered patchy late gadolinium enhancement (LGE) was seen within the left ventricular myocardium, particularly in the left ventricular anterior wall and interventricular septum (Figure 3D). T1 mapping revealed a markedly increased T1 value at basal IVS from 1,123 to 1,260 ms (Figures 3E,F). The reference native T1 value of our 1.5T scanner was 1,035 ms. Intraoperative transesophageal echocardiography (TEE) demonstrated well-corrected RVOT (Figures 2G,H and Supplementary Videos 5-6).
Histologic features. (A) Hematoxylin-Eosin staining showed myocardial fiber hypertrophy, degeneration and necrosis of some myocardial fibers, and hyaline degeneration (100x magnification). (B) Masson staining showed fibrous tissue hyperplasia (100x magnification).
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A dumbbell-shaped RV and flow acceleration at the RVOT were observed during systole (Figures 3A,B and Supplementary Video 4). Intraoperative transesophageal echocardiography (TEE) demonstrated well-corrected RVOT (Figures 2G,H and Supplementary Videos 5-6). The pathology report revealed myocardial fiber hypertrophy, degeneration and necrosis of some myocardial fibers, fibrous scar formation, local subendocardium fibrous tissue hyperplasia, hyaline degeneration, and hyperplasia of elastic fibers in the focal subendocardium, all of which were consistent with HCM (Figure 4).