Tricuspid Atresia

Epidemiology and Anatomy

Tricuspid atresia is characterized by a complete lack of communication between the right atrium and right ventricle that results from congenital agenesis of the tricuspid valve (Figure 1). In an otherwise anatomically normal heart, tricuspid agenesis would result in absent blood flow to the pulmonary artery and is therefore incompatible with life. To allow for oxygenation of blood, 100% of patients with tricuspid atresia have additional cardiac lesions. Tricuspid atresia occurs in approximately 79 of every 1,000,000 live births.

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Figure 1: Tricuspid Atresia (Type I). Image from https://en.wikipedia.org/wiki/Tricuspid_atresia#/media/File:Tricuspid_at...

An atrial septal defect (ASD) and hypoplastic right ventricle are found in 100% of tricuspid atresia patients, and the vast majority of patients also have a ventricular septal defect (VSD). The ASD is commonly an enlarged patent foramen ovale and allows for blood to exit the right ventricle; this communication is necessary for deoxygenated blood to enter the left atrium (via a right-to-left shunt), where it mixes with oxygenated blood. The blood from the left atrium will then enter the left ventricle, and if a VSD is present, this mixed blood will enter both the systemic and pulmonary circulations.

In the absence of a VSD, however, a patent ductus arteriosus (PDA) and collateral vessels are the only sources of pulmonary circulation. Additionally, increased blood flow through the left ventricle results in an enlarged and hypertrophied left ventricle.

Tricuspid atresia is classified depending on the orientation of the great arteries. Type I is characterized by normal orientation of the great arteries, whereas Type II is characterized by transposition of the great arteries (TGA).

With Type I tricuspid atresia, pulmonary blood flow is greatly diminished and is dependent upon a variably present VSD and a patent ductus arteriosus. Pulmonary stenosis may also be present, and the degree of pulmonary stenosis combined with the extent of ductus arterosus blood flow will determine the amount of blood that enters the pulmonary circulation.

In Type II tricuspid atresia, however, a VSD is invariably present, and pulmonary blood flow can be accentuated.

Clinical Presentation:

If not diagnosed in utero, tricuspid atresia commonly presents with cyanosis and a heart murmur, and the degree of pulmonary blood flow determines the timing of cyanosis. In the event of decreased pulmonary blood flow, cyanosis commonly presents on the first day of life. Patients with excess pulmonary blood flow will present with signs of heart failure and cyanosis later (but still within the first few days of life).

The cyanosis results from a mixing of oxygenated and deoxygenated blood in the left atrium, and the quality of murmur heard depends upon the additional heart defects that are present. All cases of tricuspid atresia are characterized by a single second heart sound, and if a VSD is present, a holosystolic murmur. If the ductus arteriosus is patent, a continuous murmur can be heard, and depending on the degree of pulmonary stenosis, a systolic ejection murmur may also be present.

Differential Diagnosis:

 The differential diagnosis includes cyanotic heart anomalies. These include the following: Tetralogy of Fallot, transposition of the great arteries, total anomalous pulmonary venous return, truncus arteriosus, hypoplastic left heart, pulmonary atresia, and tricuspid atresia.  

Workup:

Chest X-Ray:

  • If decreased pulmonary circulation:
    • No characteristic appearance of heart shadow
    • Decreased lung markings
  • If increased pulmonary circulation:
    • Enlarged heart shadow
    • Increased lung markings

EKG:

  • Left axis deviation due to hypoplastic right ventricle and enlarged left ventricle
  • Pathognomic findings in setting of cyanosis:
    • Tall p-waves (indicating atrial hyperplasia)
    • Left axis deviation
    • LV hypertrophy

ECHO:

  • Direct visualization of the atretic tricuspid valve, atrial septal defect, and additional present cardiac structural anomalies.

Therapy:

Medical Management:

  • Supportive care
  • Maintaining adequate pulmonary blood flow
    • If a ductal dependent lesion, prostaglandin E is administered to maintain a patent ductus arteriosus.
    • If TGA is present, there will likely be increased pulmonary blood flow, and signs of heart failure may be present. These patients may benefit from diuretic therapy.

Surgical Management:

Three stages:

Stage 1: Regulating pulmonary blood flow to either increase pulmonary blood flow (and decrease hypoxemia) or relieve excess pulmonary blood flow (and decrease symptoms of heart failure).

BLALOCK-TAUSSIG SHUNT

  • Procedure: A shunt is placed between a branch of the aorta and the pulmonary artery. This effectively replaces the ductus arteriosus to allow for blood flow into the pulmonary vasculature.
  • Timing: Depends on degree of cyanosis but the shunt is typically placed within the first weeks of life.


Blalock–Taussig shunt – A/ original procedure – B/ modified procedure
https://en.wikipedia.org/wiki/Blalock%E2%80%93Taussig_shunt

BANDING PROCEDURE 

  • Procedure: In the event that there is excess pulmonary blood flow (i.e. Type II), pulmonary blood flow may be regulated by a banding procedure. In this procedure, a band is placed around the pulmonary artery to narrow the artery and restrict flow to the pulmonary vasculature. 

Stage 2:

 HEMI-FONTAN/GLENN:

  • Procedure: A direct connection between the superior vena cava and the pulmonary artery is made. Often the previously placed BT shunt is removed at this point.
  • Timing: 3-6 months of age

Stage 3:

FONTAN

  • Procedure: A direct connection between the inferior vena cava and the pulmonary artery is made. Combined with the Glenn procedure, this procedure makes it so that all of the systemic blood flow returns directly to the pulmonary artery and bypasses the right atrium.
  • Timing: Typically at 18-36 months.

In some cases, cardiac transplantation may be indicated

Common complications post-Fontan procedure:

  • Elevated systemic venous pressures
    • Due to lack of ventricular pump pushing blood into the pulmonary vasculature
  • Arrhythmias
  • Ventricular Dysfunction
  • Thromboembolic events
  • Protein-losing enteropathy
    • 5 year survival is ~50%
  • Restrictive lung disease
  • Liver disease

Prognosis:

  • 79% survival rate at 13 years after Fontan procedure
  • Patient will need to be carefully followed by a cardiologist long-term to make medication adjustments, measure oxygen levels, and determine if/when it is time for the next operation
  • Some young adults are candidates for Fontan revision to prevent rapid progression of some of the long term complications and/or to delay the need for cardiac transplantation 

References:

  1. Rao, P. Syamasundar. "Diagnosis and management of cyanotic congenital heart disease: part I." The Indian Journal of Pediatrics 76, no. 1 (2009): 57-70.
  2. Hoffman, Julien IE, and Samuel Kaplan. "The incidence of congenital heart disease." Journal of the American College of Cardiology 39, no. 12 (2002): 1890-1900.
  3. Children’s Hospital of Philadelphia Department of Cardiology: http://www.chop.edu/conditions-diseases/tricuspid-atresia/about#.VfxwALQeNFI
  4. American Heart Association: http://www.heart.org/HEARTORG/Conditions/CongenitalHeartDefects/AboutCongenitalHeartDefects/Single-Ventricle-Defects_UCM_307037_Article.jsp
  5. E-medicine: Tricuspid Atresia
  6. Uptodate: Tricuspid valve (TV) atresia
  7. Uptodate: Management of patients post-Fontan procedure