A case of subvalvular pulmonary stenosis differentiated from a double-chambered right ventricle by transesophageal echoc
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IMAGE–CARDIOLOGY
A case of subvalvular pulmonary stenosis differentiated from a double‑chambered right ventricle by transesophageal echocardiography: importance of detecting the pulmonary valve Toshimitsu Kato1 · Noriaki Takama2 · Tomonari Harada2 · Masaru Obokata2 · Koji Kurosawa3 · Masahiko Kurabayashi2 · Masami Murakami1 Received: 31 March 2020 / Accepted: 10 July 2020 © The Japan Society of Ultrasonics in Medicine 2020
A 57-year-old woman presented with shortness of breath and leg edema. A grade 2/6 systolic ejection murmur was auscultated at the second left sternal border. Transthoracic echocardiography showed a left ventricular ejection fraction of 65%. The parasternal short-axis view showed regional wall thickening around the right ventricular outflow tract (RVOT), indicating a double-chambered right ventricle (DCRV) (Fig. 1a). Cardiac magnetic resonance imaging (MRI) indicated RVOT stenosis (Fig. 1b). The apical threechamber echocardiographic view revealed a doubly committed subarterial ventricular septal defect (VSD) (Fig. 1c). Transesophageal echocardiography (TEE) detected the pulmonary valve (PV) and revealed subvalvular pulmonary stenosis (SubPS), rather than DCRV (Fig. 1d, e). Color Doppler imaging showed systolic VSD jet and mosaic flow in the SubPS and detected moderate aortic regurgitation due to slight right coronary cusp prolapse. Right heart catheterization demonstrated a pressure gradient of 60 mmHg in the SubPS. Right ventricular abnormal fibromuscular tissue resection, VSD patch closure, and aortic valve replacement were performed. Her postoperative course was uneventful. Both SubPS and DCRV are phenotypes of congenital or acquired structural heart disease [1]. SubPS is a form of fibromuscular stenosis in the distal RVOT directly below the PV. DCRV is a form of RVOT obstruction formed by the development of the trabecular muscle bundle, dividing the
proximal and distal chambers [2]. The obstruction level is different within the right ventricular cavity and is associated with VSD upon diagnosis in 95% of cases. Perimembranous deficiency is the most common type of VSD complicating DCRV, occurring in 80% of cases [3]. In patients with VSD, the most commonly observed cardiac abnormality is RVOT stenosis. Its prevalence increases from 4.3% to 7.8% in pediatrics to adults, indicating progressive obstruction by the fibromuscular tissue [4]. In the present case, the VSD was a doubly committed subarterial type, positioned just below the arterial valves. The VSD jet blew toward the free wall of RVOT just below the pulmonary artery and caused hemodynamic stress, leading to the overdevelopment of fibromuscular tissue and formation of SubPS. Preoperative differentiation of SubPS from DCRV reduces the risk of PV injury [5]. The PV could not be detected around the distal RVOT, which was analogous to the distal chamber of DCRV, on transthoracic echocardiography. It was difficult to evaluate the RVOT in detail on cardiac MRI; this case similarly appeared to be DCRV. TEE was most useful for morphologically
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