Basics
Description
Anatomic hallmark is anterior malalignment of infundibular (outlet) septum which results in
- A large and unrestrictive ventricular septal defect (VSD)
- Various degrees of right ventricular outflow tract obstruction (RVOTO)
- Overriding aorta
- Right ventricular hypertrophy (RVH) secondary to exposure to systemic pressure
Epidemiology
- The most common cyanotic congenital heart disease
- 3.5 " 10% of all congenital heart disease
Risk Factors
Genetics
Some cases of tetralogy of Fallot are associated with a chromosome 22q11 microdeletion.
Pathophysiology
- Severity of clinical signs and symptoms depends on the degree of RVOTO and related right-to-left shunt at the VSD.
- Physiology is a spectrum ranging from too little pulmonary blood flow due to severe RVOTO ( "blue tet " ) to moderate pulmonary overcirculation ( "pink tet " ).
Commonly Associated Conditions
- May be associated with other syndromes including trisomy 21, Alagille syndrome, fetal alcohol syndrome, and those involving a variety of limb abnormalities.
- Tetralogy of Fallot may also be associated with midline abdominal defects (e.g., omphalocele) as in the pentalogy of Cantrell.
Diagnosis
Signs & Symptoms
- Heart murmur in the newborn period
- Various degrees of progressive cyanosis
- Paroxysmal cyanosis, especially when crying or during and after physical activity
Physical Exam
- Cyanosis may be present at birth or may appear later during infancy or childhood as a result of progressive RVOTO.
- Normal S1 and single loud S2 secondary to a more anteriorly located aorta
- Systolic ejection murmur at left upper sternal border secondary to RVOTO
Diagnostic Tests & Interpretation
- Electrocardiography
- Right axis deviation (+90 " 180 degrees)
- RVH
- Chest radiograph
- Right aortic arch (30%)
- Decreased pulmonary vascular markings
- Boot-shaped heart (coeur en sabot) with concave main pulmonary artery segment
- Echocardiogram
- Anterior malalignment VSD
- Presence of additional VSDs
- Degree of infundibular stenosis
- Presence of valvar pulmonary stenosis and/or branch pulmonary artery stenosis
- Overriding aorta, arch sidedness
- Coronary artery anatomy
- Cardiac catheterization
- Generally not indicated unless there is concern regarding the branch pulmonary artery anatomy, coronary anatomy, or additional VSDs that need to be defined before surgery
Differential Diagnosis
- Tetralogy of Fallot should be considered in all infants with a heart murmur and/or various degrees of cyanosis as well as acyanotic infants or children with a history of hypercyanotic episodes.
- Other forms of cyanotic congenital heart disease should be considered, including the following:
- Double outlet right ventricle (DORV),
- Transposition of the great arteries (TGAs)
- Pulmonary atresia with a VSD (PA-VSD).
Treatment
Medication
- Hypercyanotic episodes ( "tet spells " )
- The goal is to increase preload and promote pulmonary blood flow.
- Knee-chest position
- Intravenous fluid bolus
- NaHCO3
- Oxygen
- Morphine sulfate (0.1 mg/kg IV or IM)
- Beta-blocker (esmolol infusion for immediate therapy, propranolol for long-term prophylaxis)
- Phenylephrine (0.02 mg/kg IV)
- Polycythemia: oral iron supplement to prevent iron deficiency and microcytosis
- Subacute bacterial endocarditis (SBE) prophylaxis
Surgery/Other Procedures
- Palliative surgery: Blalock-Taussig systemic-to-pulmonary artery shunt (also known as the Blalock-Taussig-Thomas shunt)
- Corrective surgery: VSD patch closure and right ventricular outflow tract reconstruction
Ongoing Care
Prognosis
- 35-year survival is approximately 85%.
- More than 90% of children with tetralogy of Fallot are expected to survive to adulthood.
- Higher risk of adverse outcomes in patients with repair at age >3 years.
- There is a higher risk of developmental delay in children with tetralogy of Fallot (as with all congenital heart disease).
- Residual hemodynamic abnormalities are common:
- Pulmonary insufficiency (with transannular patch repair)
- Residual RVOTO
- Right ventricular dysfunction in adulthood due to chronic volume overload
- Left pulmonary artery stenosis is particularly common in tetralogy of Fallot.
- Residual VSD
- Conduction abnormalities (e.g., complete heart block, atrial and ventricular tachyarrhythmias)
- Incidence of sudden death is 2.5% per decade of follow-up and is generally attributed to ventricular arrhythmias
- The need for reintervention (pulmonary valve insertion) increases after the 2nd decade of life.
- Right ventricular end-diastolic volume >150 mL/m2, QRS > 180 ms, history of tachyarrhythmias, RVOTO, exercise intolerance, syncope
- Surgical versus transcatheter intervention (Melody valve)
Complications
Preoperatively
- Paroxysmal hypoxic episodes (i.e., hypercyanotic episodes, also called tet spell)
- Bacterial endocarditis
- Cerebrovascular accident secondary to cyanosis, polycythemia, and microcytic anemia
Postoperatively
- Right ventricular dysfunction
- Ventricular arrhythmias
- Sudden death (ventricular arrhythmias and/or complete heart block)
Additional Reading
- Apitz C, Webb G, Redington A. Tetralogy of Fallot. Lancet. 2009;374(9699):1462 " 1471. [View Abstract]
- Cobanoglu A, Schultz JM. Total correction of tetralogy of Fallot in the first year of life: late results. Ann Thorac Surg. 2005;74(1):133 " 138. [View Abstract]
- Geva T. Indications for pulmonary valve replacement in repaired tetralogy of Fallot: the quest continues. Circulation. 2013;128(17):1855 " 1857. [View Abstract]
- Hirsch JC, Bove EL. Tetralogy of Fallot. In: Mavroudis C, Backer CL, eds. Pediatric Cardiac Surgery. 3rd ed. Philadelphia: Mosby; 2003:383 " 397.
- Martinez RM, Ringewald J, Fontanet HL, et al. Management of adults with Tetralogy of Fallot. Cardiol Young. 2013;23(6):921 " 932. [View Abstract]
- Murphy AM, Cameron DE. The Blalock-Taussig-Thomas collaboration. A model for medical progress. JAMA. 2008;300(3):328 " 330. [View Abstract]
- Siwik ES. Moss and Adams Heart Diseases in Infants, Children and Adolescents. 5th ed. Baltimore: Williams & Wilkins; 2001:880 " 902.
- Walker WT, Temple IK, Gnanapragasam JP, et al. Quality of life after repair of tetralogy of Fallot. Cardiol Young. 2002;12(6):549 " 553. [View Abstract]
- Warnes CA, Williams RG, Bashore TM, et al. ACC/AHA 2008 guidelines for the management of adults with congenital heart disease: a report of the American College of Cardiology/American Heart Association Task Force on Practice Guidelines (writing committee to develop guidelines on the management of adults with congenital heart disease). Circulation. 2008;118(23):e714 " e833. [View Abstract]
Codes
ICD09
- 745.2 Tetralogy of fallot
ICD10
- Q21.3 Tetralogy of Fallot
SNOMED
- 86299006 Tetralogy of Fallot (disorder)
- 253515003 Ventricular septal defect in Fallot 's tetralogy
- 253513005 Tetralogy of Fallot with pulmonary atresia (disorder)
- 253512000 Tetralogy of Fallot with pulmonary stenosis (disorder)
FAQ
- Q: What is the etiology of the tet spell?
- A: There is an increase in resistance to flow through the right ventricular outflow tract and/or pulmonary vascular bed that leads to a dramatic decrease in pulmonary blood flow and increased right-to-left shunt at the level of the VSD. Therefore, treatment should be aimed at increasing pulmonary blood flow either by decreasing pulmonary vascular resistance (e.g., oxygen, morphine), increasing systemic vascular resistance (e.g., knee-chest position, phenylephrine), or decreasing dynamic obstruction by decreasing heart rate and thus increasing right ventricular preload (e.g., beta-blockers).
- Q: When is an optimal time for surgical repair of tetralogy of Fallot?
- A: Surgical correction should be guided by symptoms. Progressive hypoxemia or recurrent tet spells indicate a need for surgical intervention. A "pink tet " can be referred for elective repair in early infancy (3 " 6 months) and before the end of the 1st year of life.