Uhl's Anomaly with Absent Tricuspid Valve in an Infant.

Uhl's anomaly is characterized by absence of the myocardial layer of the right ventricle, with opposition of the endocardium and epicardium. It is rarely associated with other congenital malformation. Here, we reported the rare association of Uhl's anomaly with absent tricuspid valve in an infant.

INTRODUCTION

Uhl's anomaly is characterized by the partial or complete absence of the myocardium of the right ventricle. A review in 1993 found 84 reported cases in the literature, since the beginning of 20th century. It may be isolated or associated with other cardiac malformation. An unguarded tricuspid valve is a rare congenital anomaly described in only a few antemortem case reports.[123] Here, we report a rare case of Uhl's anomaly with unguarded tricuspid valve orifice with free tricuspid regurgitation in the infant.

CASE REPORT

A 2-month-old male infant weighing 3.15 kg, presented with a history of breathlessness. He was a full-term normal vaginal delivery at home. On general examination, afebrile, tachypneic, cyanosis, and clubbing were present, and all peripheral pulses were present. His vitals were heart rate: 122/m, respiratory rate: 52/m, blood pressure: 108/88 mmHg and oxygen saturation: 80%. On auscultation, ejection systolic murmur was best heard in the upper left parasternal area. No third heart sound or diastolic murmur was heard. There was mild hepatomegaly. Chest X-ray showed an enlarged cardiac silhouette (cardiothoracic >0.5) and decreased pulmonary vasculature. Electrocardiography showed sinus rhythm, normal QRS axis with the right atrial hypertrophy. Transthoracic two-dimensional echocardiography reveals situs solitus, enlarged right atrium and ventricle, no definitive right ventricular wall and small diverticulum of the right ventricular outflow tract. Absent tricuspid valve with free tricuspid regurgitation [Figure 1]. The ventricular function was poor with paradoxical septal motion. The right ventricle was enlarged, and its wall was thin and hypokinetic. There was no active the right ventricular contraction. There was no thinning of right ventricle wall with each systole. Small size (2 mm) perimembranous type ventricular septal defect with left to right shunt (gradient 60 mmHg) was present. Large size (5 mm) ostium secundum type of atrial septal defect with the right to left shunt was present. No pericardial effusion.

Figure 1

Subcostal long axis view shows the dilatation of the right atrium with right ventricle and absent tricuspid valve. It also shows the thinning of right ventricular wall

DISCUSSION

Uhl's anomaly is a rare cardiomyopathy characterized by a thin walled dilated right ventricle due to the absence of myocardium. In 1902, Osler reported a heart with a very thin wall like a parchment. Subsequently, in 1949, Uhl reported the similar type of case after an autopsy of old infant and later in 1979, Fontaine et al. described a condition called “arrhythmogenic right ventricular dysplasia” (ARVD) characterized by local deficiency or fibro-fatty replacement of the right ventricular myocardium. Uhl's anomaly and ARVD are different diseases which has separate and different morphological entities. In Uhl's anomaly, the affected wall does not have a fat tissue, and endocardial and epicardial layer lie parallel to each other whereas in ARVD, is the replacement of myocardial cell by fibrous fatty tissue.[2345] Uhl's anomaly has been reported in identical twins and has been diagnosed in utero.[6] A failure during embryonic development of the right ventricular myocardium occurs is a possible cause. Recently, the hypothesis that the right ventricular myocardium may be replaced due to a process of apoptosis of the myocardiocytes has been cogitated and supported by studies of molecular biology. Some Authors suggested that overexpression of vascular endothelial growth factor, mainly cardiomyocytes may be responsible for impaired development of the ventricular myocardium.[78] It may be associated with other congenital cardiac malformation such as tricuspid valve anomalies, pulmonary atresia, patent ductus arteriosus, atrial septal defect and Ebstein's anomaly.[4] Congenitally unguarded tricuspid orifice is a rare anomaly, and few cases of antemortem diagnosis have been reported in the literature. Kanjuh et al.[9] reported the partial or complete absence of tricuspid valvar tissue diagnosed on fetal echocardiography. In Uhl's anomaly, mainly there is a lack of right ventricular contraction and hemodynamically right ventricle act as a transition zone between the right atrium and pulmonary trunk. The thin-walled right ventricle balloons aneurysmally with each systole. The forward flow to the pulmonary circulation is driven by vigorous paradoxical septal motion and right atrial contraction.[8] Whereas in the unguarded tricuspid orifice, pulmonary circulation is maintained by the pumping action of the right atrium or the outflow tract because of the poor right ventricular contractile function. The right atrium can assume enormous proportions. Right-to-left shunting can occur through the patent foramen ovale.[2] Hemodynamically our case as having very poor right ventricular function as well as right atrium workload is increased for feeding the pulmonary vessels.

The clinical finding in Uhl's anomaly is heart failure with complaints of palpitation, syncope, tachycardia, and sudden death. Arrhythmia and conduction disturbances are not the most common feature o due to the absence of residual foci to transmit anomalous electrical activity. On physical examination, cyanosis, and jugular venous disten-sion with a dominant “a” wave is present. Cardiac auscultation usually reveals a decrease in the intensity of the heart sound, especially the first heart sound with widely split second heart sound. Third heart sound is heard by passive flow into the poorly compliant right ventricle. A typical pansystolic murmur of tricuspid insufficiency may be present, but the patient may have other nonspecific murmur.[1011] Auscultation may vary if other associated cardiac malformation is present.

The X-ray shows normal pulmonary vascularity and cardiomegaly. The ECG shows right atrial p waves. Echocardiography identifies a large right ventricle with an akinetic free wall, brisk paradoxical septal motion of the ventricular septum and normal tricuspid leaflets in Uhl's anomaly.[12] Successful surgical repair of Uhl's anomaly has been reported. The most frequent approaches were exclusion of right ventricle by closure of tricuspid valve orifice with atrial septostomy and bi-directional Glenn shunt. A modification of this procedure combines with atrial septostomy and bi-directional Glenn shunt with partial right ventriculotomy also called as “one-and-a-half ventricular repair.” Successful complete correction by cardiac transplantation has also been reported. It is unclear that the infant will benefit from bi-directional Glenn shunt or one-and-a-half ventricular repair.[1314] In view of severe right ventricular dysfunction, valve repair, or replacement is not helpful. Heart transplantation remains an only option in this case.

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Conflicts of interest

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