Tricuspid Atresia

Abstract

Tricuspid atresia (TA) is a rare congenital heart defect. Prenatal diagnosis can be done on the four-chamber view, which shows an atretic tricuspid valve with no mobility and absence of flow across it. In most cases, there is a ventricular septal defect and a variable degree of diminished development of the right ventricle and pulmonary artery. The association of TA with extracardiac and chromosomal abnormalities is about 20% and 5%, respectively. TA is frequently associated with other cardiac malformations (30% of cases, especially transposition of great arteries and pulmonary obstruction). Fetal karyotyping should be considered. A careful examination of the cardiac and extracardiac anatomy is mandatory, with a follow-up examination every 2 to 4 weeks to assess the foramen ovale and the development of the pulmonary artery. The obstetric management should not be changed in the absence of hydrops. TA requires stratified and palliative surgery (the Fontan operation) in the child. Neonatal mortality is approximately 10%. Survival progressively decreases during early and later childhood.

Keywords

tricuspid atresia, ventricular septal defect, pulmonary artery, Fontan procedure

Introduction

Tricuspid atresia (TA) is a rare form of congenital heart disease (CHD) that usually involves severe hypoplasia of the right ventricle. Prenatal diagnosis of TA and associated intracardiac and extracardiac anomalies is possible with a high degree of accuracy.

Disease

Definition

TA is defined by the lack of connection between the right atrium and the right ventricle. The most common form is the absence of the tricuspid valve, which is replaced by fibrous tissue. Rarely, a dysplastic imperforate tricuspid valve is present. In most cases, there is a defect in the membranous portion of the interventricular septum (ventricular septal defect [VSD]) of variable size, which establishes the degree of development of the right ventricle and pulmonary artery. In most cases of TA, there is a variable grade of right ventricle hypoplasia, and TA can be classified as a form of hypoplastic right heart syndrome.

Prevalence and Epidemiology

TA is a rare CHD. The estimated incidence is 1 : 25,000 live births. In fetal series, the incidence of TA is low, ranging from 3% to 4% of all prenatally diagnosed CHDs.

Etiology and Pathophysiology

The etiology of TA is multifactorial. Associated extracardiac and chromosomal abnormalities are present in about 20% (extracardiac abnormalities) and 5% (chromosomal abnormalities) of cases. TA is associated with other cardiac malformations in approximately 30% of cases, with transposition of great arteries and pulmonary obstruction being the more commonly associated anomalies. TA is also frequently associated with fetal growth restriction.

Perimembranous VSDs are very common with TA. The size of the foramen ovale and the VSD constitute the two main prognostic factors in the fetus ( Fig. 77.1 ).

1.

If the foramen ovale is normal, a proper right-to-left shunt is maintained (right atrium–left atrium–left ventricle). In contrast, if the foramen ovale is restrictive, the risk of hydrops is high.
2.

If there is a moderate to large VSD, the right ventricle and the pulmonary artery receive blood from the left ventricle (left ventricle–right ventricle–pulmonary artery). In contrast, if there is no VSD or a very small VSD, the right ventricle and pulmonary artery are hypoplastic, and the pulmonary artery receives retrograde flow from the ductus arteriosus.

Manifestations of Disease

Clinical Presentation

A newborn with TA needs immediate care in a tertiary center. Arterial oxygen content primarily depends on the respective proportion of pulmonary and systemic venous return that enters the left ventricle. If there is no VSD, the survival of these neonates depends on the patency of the ductus arteriosus as the only source of pulmonary flow. In the presence of a large VSD, pulmonary flow can be efficiently maintained through the defect, but such cases are at higher risk of cardiac failure because of high cardiac output. When TA is associated with transposition of the great arteries, the neonate may not have significant cyanosis, but there is still a risk of cardiac failure, and there is a risk of aortic coarctation or interruption.

Imaging Technique and Findings

Ultrasound.

The ultrasound diagnosis of TA can be made on the four-chamber view. The key diagnostic feature is a nonpatent tricuspid valve. The valve has an abnormal aspect, with thickening, increased echogenicity, and little or no mobility ( Fig. 77.2 and ). As a consequence, there is commonly an associated small right ventricle with a dominant left ventricle. As previously mentioned, a perimembranous VSD can be identified in most cases ( ). The presence of the VSD determines the growth of the right ventricle and pulmonary artery.