Prenatal ultrasonographic diagnosis of Uhl anomaly

Introduction

Uhl anomaly is an extremely rare congenital heart disease with an unknown underlying etiology. It is characterized by the complete or partial constitutional absence of the myocardial layer in the right ventricle, which is replaced by nonfunctional fibroelastic tissue [5, 6, 9, 12, 14]. Only 84 cases have been reported [4], and cases of prenatal diagnosis are extremely rare. To our knowledge, only three case reports on the prenatal diagnosis of Uhl anomaly have been published [2, 3, 15]. In two of these case reports [2, 15], the condition was initially suspected as Ebstein anomaly and its variant type, and we thought the rarity of Uhl anomaly may make prenatal diagnosis difficult.

Case

A 35-year-old woman (gravida 2, para 2) was referred to another hospital at 26 weeks because of a suspected fetal cardiac anomaly. A fetal growth was normal, and in the four-chamber view, the cardiothoracic area ratio (CTAR) was 43%, indicating fetal cardiomegaly; moreover, the ventricular septal aneurysm at the apex showed paradoxical motion. Color Doppler examination indicated severe tricuspid and pulmonary regurgitation, which resulted in a circular shunt, where blood flowed through the ductus arteriosus to the pulmonary arteries, retrograded through the pulmonary and tricuspid valve, across the patent foramen ovale, and out from the aorta. Flow through the apical septal aneurysm was also observed and was suspected as another cause of the circular shunt (Figure 1). The tricuspid valve and its position seemed normal; hence, Ebstein anomaly or tricuspid dysplasia was excluded. The pulmonary artery ascended normally from the right ventricle and showed a normal course and branching; therefore, other causes of circular shunt such as pulmonary valve dysplasia, absent pulmonary valve, and aortopulmonary window were excluded. At 35 weeks, the CTAR increased to 48%, and she was referred to our hospital for perinatal care of the fetal circular shunt with ventricular septal aneurysm at 36 weeks. At admission, the apical myocardium of the right ventricle appeared paper thin, with apical dilation and akinesia, and without normal trabeculation in the right ventricular apex (Figure 2). Severe tricuspid and pulmonary regurgitation persisted. Based on these echocardiographic findings, we diagnosed the fetus with Uhl anomaly, ventricular septal aneurysm, and a circular shunt. No additional structural anomalies were observed after the complete anatomical survey. The fetus was carefully followed-up with serial ultrasonographic examinations. Although the CTAR gradually increased, no signs of progressive cardiac failure were noted throughout the pregnancy. Furthermore, fetal arrhythmia was not observed.

Figure 1

Echocardiographic findings at 26 weeks of gestation.

Tricuspid regurgitation and shunt flow through the ventricular aneurysm were noted during the ventricular systolic period. These were the cause of a circular shunt in addition to pulmonary regurgitation at the ventricular diastolic period. Ant=anterior; Post=posterior; Rt=right; Lt=left; RA=right atrium; LA=left atrium; RV=right ventricle; LV=left ventricle; TR=tricuspid regurgitation.

Figure 2

Four-chamber view of the fetus at 36 weeks of gestation.

A four-chamber view of the fetus is shown. A thinned right ventricular wall and the absence of normal trabeculation of the right apical ventricular are noted. Ant=anterior; Post=posterior; Rt=right; Lt=left; RA=right atrium; LA=left atrium; RV=right ventricle; LV=left ventricle.

We decided to perform an elective cesarean section at 36 weeks and 6 days of gestation in collaboration with doctors from other departments, such as neonatal cardiology and cardiovascular surgery. Because a circulatory failure caused by circular shunt will need an emergency surgical intervention immediately after birth.

A male neonate was delivered, weighing 3074 g, with Apgar scores of 5 and 5 points at 1 and 5 min, respectively. The neonate had severe dyspnea and was immediately intubated and received mechanical ventilation. Physical examination indicated continuous heart murmurs. Chest radiography showed severe cardiomegaly. On echocardiography, an enlarged right ventricular cavity with severe hypokinesia and a ventricular septal aneurysm, mild tricuspid regurgitation, and mild continuous pulmonary regurgitation were observed (Figure 3). Thus, the diagnosis of Uhl anomaly was confirmed, and co-existing cardiac anomalies were excluded. The patient underwent main pulmonary artery ligation on that day because of the lack of improvement of acidemia due to the circular shunt. After the surgery, the acidemia improved; however, on the 9^th day, he underwent a ductus arteriosus ligation and a central shunt was created using a 4-mm-diameter expanded polytetrafluoroethylene tube for progressive lung congestion. The postoperative course was uneventful. During the 3-month follow-up, the patient appeared well and was awaiting a staged Fontan operation involving a bidirectional Glenn procedure.

Figure 3

Echocardiographic findings of the neonate.

A four-chamber view of the neonate is shown. During the cardiac cycle, a severely hypokinetic enlarged right ventricle and a ventricular septal aneurysm were observed. RA=right atrium; LA=left atrium; RV=right ventricle; LV=left ventricle.

Discussion

In the diagnosis of Uhl anomaly, echocardiography plays an important role. The characteristic findings include an enlarged right ventricular cavity with a thin ventricular wall and without apical trabeculation. The tricuspid valve annulus is markedly dilated. The left heart findings appear normal, and the intraventricular septum shows paradoxical motion. These characteristic ultrasonographic findings were also noted in our case. In three prenatal diagnosed cases, an enlarged right atrium and ventricle, and tricuspid regurgitation were also noted [2, 3, 15]. However, two of these cases were initially suspected as Ebstein anomaly [2, 15]. While the rarity of Uhl anomaly may make prenatal diagnosis difficult, evaluating the tricuspid valve will enable clinicians to differentiate Uhl anomaly from Ebstein anomaly or tricuspid valve dysplasia. The characteristic ultrasonographic findings of Ebstein anomaly include the displacement of the septal leaflet of the tricuspid valve and the systolic regurgitant jet flow from the middle of the right ventricle. Moreover, although the attachment of the leaflet of the tricuspid valve is normal in tricuspid valve dysplasia, the thickened valve leaflets do not close properly and cause systolic regurgitant jet flow from the tricuspid valve annulus. In our case, the tricuspid valve and its position seemed normal; thus, it was possible to differentiate Ebstein anomaly or tricuspid valve dysplasia from an Uhl anomaly.

Various types of surgical repair have been successfully performed for Uhl anomaly [1, 10, 16]. In cases with a circular shunt, emergency surgical intervention is often needed [8, 11]. Therefore, in our case, an elected cesarean section was performed with mechanical ventilation and prostaglandin E1 administration. We also planned to proceed with main pulmonary artery and ductus arteriosus ligation, and the creation of a central shunt if it was difficult to maintain the systemic circulation after birth. In addition to the typical circular shunt, in our case, the shunt through the ventricular septum involved an aneurysmal rupture. The association of ventricular septum aneurysmal rupture with Uhl anomaly is unclear, and it may be difficult to diagnose it due to the paradoxical motion of ventricular septum without careful ultrasonographic observation.

The etiology of Uhl anomaly remains unclear. It was initially considered as congenital development failure of the right ventricle during the early stages of the embryo. However, recent reports suggest that this disease may be associated with apoptosis in the right ventricular myocardium [7, 13]. In our serial ultrasonographic observations, the paper-thin right ventricular wall and lack of trabeculation were not clearly visualized at 26 weeks, but became apparent at 36 weeks. These findings support the hypothesis of James et al. [7].

In conclusion, although Uhl anomaly is extremely rare, detailed fetal echocardiography may enable its prenatal diagnosis. Moreover, a greater understanding and correct prenatal diagnoses of Uhl anomaly can help in selecting and preparing for the treatment of neonates.