Tricuspid atresia
Tricuspid atresia is a form of congenital heart disease whereby there is a complete absence of the tricuspid valve.[2] Therefore, there is an absence of right atrioventricular connection.[2] This leads to a hypoplastic (undersized) or absent right ventricle. This defect is contracted during prenatal development, when the heart does not finish developing. It causes the systemic circulation to be filled with relatively deoxygenated blood. Because of this, hypoxia occurs, so other defects must occur to maintain blood flow. Because of the lack of an atrioventricular connection, an atrial septal defect (ASD) must be present to fill the left atrium and the left ventricle with blood.[3] Since there is a lack of a right ventricle, there must be a way to pump blood into the pulmonary arteries, and this is accomplished by a ventricular septal defect (VSD). The causes of tricuspid atresia are unknown.[4]
| Tricuspid atresia | |
|---|---|
| Other names | Tri atresia[1] |
 | |
| Anterior (frontal) view of the opened heart. White arrows indicate normal blood flow. (Atresic tricuspid valve labeled at bottom left.) | |
| Specialty | Medical genetics  |
A combined atrial septal defect (ASD) and a ventricular septal defect (VSD) can be present to maintain blood flow-from the right atrium, the blood must flow through the ASD to the left atrium to the left ventricle and through the VSD to the right ventricle to allow access to the lungs.
Alternatively, an atrial septal defect (ASD) with a patent ductus arteriosus may also be present, thus causing blood flow from the right atrium to the left atrium to the left ventricle to the aorta and then to the pulmonary artery. In these cases, prostaglandin E1 is used to maintain patency of the ductus arteriosus until emergency corrective surgery can be completed.
Presentation
- progressive cyanosis[3]
- poor feeding
- tachypnea over the first 2 weeks of life
- holosystolic murmur due to the VSD
- left axis deviation on electrocardiography and left ventricular hypertrophy (since it must pump blood to both the pulmonary and systemic systems)
- Normal or mildly enlarged heart
Cause
Tricuspid atresia is caused by complete absence of the tricuspid valve.[2] The underlying cause of this absence remains unknown.[4] This prevents direct blood flow between the right atrium and the right ventricle.[2] This causes the foramen ovale to remain open after birth, leading to atrial septal defect.[3]
Pathophysiology
As there is no communication between the right atrium and the right ventricle, there must be an atrial septal defect to allow blood to flow into the left cardiac chambers. Due to the lack of blood flow into the right ventricle, it will be hypoplastic. In most cases, there will also be a ventricular septal defect allowing some blood into the pulmonary circulation. Due to the lack of blood flow into the pulmonary circulation, there is poor oxygenation of blood, leading to progressively worsening cyanosis.[5]
Diagnosis
The majority of cases can be diagnosed prenatally during a routine anomaly scan. If evidence of a congenital heart disease is found, the diagnosis can be confirmed by a foetal echocardiogram.
If it is not diagnosed prenatally, it may be diagnosed shortly after birth with physical examination, which would reveal cyanosis and murmur. Further evidence for the diagnosis can be obtained with an electrocardiogram and a chest radiograph. ECG will typically show a left axis deviation, while the chest X-ray may show pulmonary oligaemia or hyperaemia. The definitive investigation is, as in all congenital heart diseases, an echocardiogram, although the aforementioned tests along with clinical features might be sufficient for most cases.[5]
Treatment
Treatment is based on:
- PGE1 to maintain patent ductus arteriosus.[6]
- modified Blalock-Taussig shunt to maintain pulmonary blood flow by placing a Gore-Tex conduit between the subclavian artery and the pulmonary artery.
- where too much flow to the lungs is present, a pulmonary band may be placed in a first operation
- cavopulmonary anastomosis (hemi-Fontan or bidirectional Glenn) to provide stable pulmonary flow
- Fontan procedure to redirect inferior vena cava and hepatic vein flow into the pulmonary circulation.[5]
Epidemiology
Tricuspid atresia is the third most common critical congenital heart defect.[2] It is estimated to cause between 1% and 3% of all congenital heart defects.[7]
References
- "Tricuspid atresia: MedlinePlus Medical Encyclopedia". medlineplus.gov. Retrieved 28 May 2019.
- Murthy, Raghav; Nigro, John; Karamlou, Tara (2019-01-01), Ungerleider, Ross M.; Meliones, Jon N.; Nelson McMillan, Kristen; Cooper, David S. (eds.), "65 - Tricuspid Atresia", Critical Heart Disease in Infants and Children (Third Edition), Philadelphia: Elsevier, pp. 765–777.e3, doi:10.1016/b978-1-4557-0760-7.00065-6, ISBN 978-1-4557-0760-7, retrieved 2020-11-27
- Lok, Josephine M.; Spevak, Philip J.; Nichols, David G. (2006-01-01), Nichols, David G.; Ungerleider, Ross M.; Spevak, Philip J.; Greeley, William J. (eds.), "Chapter 39 - Tricuspid Atresia", Critical Heart Disease in Infants and Children (Second Edition), Philadelphia: Mosby, pp. 799–822, ISBN 978-0-323-01281-2, retrieved 2020-12-05
- "Congenital Heart Defects - Facts about Tricuspid Atresia | CDC". 2019-01-22.
- Sumal, Anoop S.; Kyriacou, Harry; Mostafa, Ahmed M.H.A.M. "Tricuspid atresia: Where are we now?". Journal of Cardiac Surgery. 35 (7): 1609–1617. Retrieved 29 April 2022.
- Aykanat, Alper; Yavuz, Taner; Özalkaya, Elif; Topçuoğlu, Sevilay; Ovalı, Fahri; Karatekin, Güner. "Long-Term Prostaglandin E1 Infusion for Newborns with Critical Congenital Heart Disease". Pediatric Cardiology.
- Hoffman Julien I.E; Kaplan Samuel (2002-06-19). "The incidence of congenital heart disease". Journal of the American College of Cardiology. 39 (12): 1890–1900. doi:10.1016/S0735-1097(02)01886-7. PMID 12084585.