Tetralogy of Fallot (TOF) is a ventricular septal defect with overriding aorta and right ventricular (RV) outflow tract obstruction and resulting RV hypertrophy. The common embryologic cause for this constellation of findings is anterior and cephalad deviation of the muscular outlet of the ventricular septum.
Usually presents in the neonatal period with a murmur, cyanosis, or both.
Diagnosed by echocardiography.
Treatment is by surgical repair. This usually consists of complete intracardiac repair typically during the neonatal or infant period. Occasionally, an aortopulmonary shunt is used palliatively before complete repair.
The most common long-term complications of complete repair are progressive pulmonary regurgitation and RV failure, atrial arrhythmias, and ventricular arrhythmias.
TOF is a congenital cardiac malformation. The key morphologic abnormality is anterior and cephalad deviation of the muscular outlet of the ventricular septum, which causes the 4 classic findings: (1) a malalignment ventricular septal defect (VSD), (2) aorta overriding the VSD, (3) right ventricular outflow tract obstruction, (4) secondary concentric right ventricular hypertrophy.
This was classically described in 1888 by Dr. Etienne-Louis Arthur Fallot, a pathologist, who coined the term "la maladie bleue" (blue-baby syndrome). The cyanosis associated with this condition is due to right-to-left shunting of deoxygenated blood at the level of the VSD. Historically, children with TOF presented with cyanosis that was progressive and life-limiting; untreated children with TOF would typically squat down, which would lead to increased pulmonary blood flow.
History and exam
Key diagnostic factors
- hypercyanotic episodes
- harsh systolic ejection murmur
Other diagnostic factors
- trisomy 21, 18, or 13
- chromosome 22q11 deletions (DiGeorge syndrome)
- Jagged1 gene mutations (Alagille syndrome)
- mutation in NKX2.5 gene
- environmental factors
- family history of congenital heart disease
1st investigations to order
- pulse oximetry
- hyperoxygenation test
Investigations to consider
- cardiac CT angiography or MRI
- cardiac catheterization
neonate with profound cyanosis and severely limited pulmonary blood flow
neonate or infant with nonremitting severe cyanosis
- Other cyanotic congenital cardiac abnormalities
- Pulmonary stenosis
- Ventricular septal defect (VSD)
- ACR Appropriateness Criteria: congenital or acquired heart disease
- Recommendations for the adult cardiac sonographer performing echocardiography to screen for critical congenital heart disease in the newborn
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