Uhl anomaly

Signs and symptoms

Infants may exhibit severe cyanosis and right heart failure at birth, though these conditions may get better as pulmonary vascular resistance decreases. The main clinical features in older patients are right heart failure symptoms and signs.

Causes

Although the precise cause of Uhl's anomaly is unknown, there have been reports of primary nondevelopment of myocytes, selective apoptosis, and cardiomyocyte overexpression of vascular endothelial growth factor. A sporadic mutation could indicate that genetics is the underlying cause.

Mechanism

The pathophysiological outcome of Uhl anomaly involves compromised diastolic filling and right ventricular contraction. Systemic venous congestion and elevated right atrial and systemic venous pressure are the results of right ventricular failure. High pulmonary vascular resistance newborns may develop functional pulmonary atresia (a result of ineffective right ventricular forward flow). Cyanosis is caused by a right-to-left shunting of blood through the patent oval foramen.

Diagnosis

Myocardial biopsies can confirm the diagnosis, which is often established by imaging tests like cardiac magnetic resonance imaging or echocardiogram.

Right atrial and right ventricular dilatation is the cause of the cardiomegaly seen on the chest radiograph. The lung fields of newborns with functional pulmonary atresia and high pulmonary vascular resistance appear oligaemic.

Right ventricular and right atrial dilatation is evident on the electrocardiogram. One can observe an epsilon (ε) wave in the right praecordial leads.

An echocardiographic evaluation reveals a thin free wall of the right ventricle without any myocardium, reduced contractility and restricted ventricle filling, dilation of the right atrium, and normal tricuspid valve attachment to the right atrioventricular junction.

Global dyskinesia of a thin-walled right ventricle, absence of myocardium at the right ventricular free wall, lack of fibrofatty infiltration, normal tricuspid valve attachment to the right atrioventricular junction, and normal left ventricular myocardium are all indicative of cardiac magnetic resonance imaging findings.

Histopathologically, nonfunctioning fibroelastic tissue replaces the myocardial layer, giving the right ventricular free wall a parchment-like appearance.

Other anomalies that can result in RV dilatation, such as Ebstein anomaly, RV arrhythmogenic dysplasia, pulmonary atresia, and anomalous pulmonary venous return, are included in the differential diagnosis of Uhl anomaly.

Treatment

When the pulmonary vascular resistance has become high and the newborn has severe cyanosis soon after birth, a brief intravenous prostaglandin E infusion is recommended. In most cases, diuretics are necessary for congestive right heart failure. Various surgical techniques have been used, such as: (1) one-and-a-half ventricular repair alongside partial right ventriculectomy and bidirectional Glenn shunt; (2) right ventricular exclusion alongside atrial septectomy as well as a bidirectional Glenn shunt (superior cavopulmonary anastomosis); and (3) cardiac transplantation.

References

References

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2. (2010). "Single Ventricle Strategy for Uhl's Anomaly of the Right Ventricle". Elsevier BV.
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4. (2002). "Successful surgical repair of Uhl's anomaly". Cambridge University Press (CUP).
5. (2019). "Uhl Anomaly in Asymptomatic Adult Woman". Ovid Technologies (Wolters Kluwer Health).
6. Cheung, Yiu-fai. (2023). "Congenital and Paediatric Acquired Heart Disease in Practice". Springer Nature Singapore.
7. Uhl, Henry S.M.. (April 15, 1996). "Uhl's Anomaly Revisited". Ovid Technologies (Wolters Kluwer Health).
8. (1997). "VEGF induces cardiovascular malformation and embryonic lethality.". American Society for Investigative Pathology.
9. (February 1, 1993). "Dysplastic conditions of the right ventricular myocardium: Uhl's anomaly vs arrhythmogenic right ventricular dysplasia.". BMJ.
10. (2015). "Uhl′s anomaly: Absence of the right ventricular myocardium". Medknow.
11. (2018). "Uhl's anomaly: A one and a half ventricular repair in a patient presenting with cardiac arrest". Saudi Heart Association.
12. (2021). "Case 288: Uhl Anomaly". Radiology.