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Virtual Pediatric Hospital: Paediapaedia: Tetralogy of Fallot (TOF) Paediapaedia: Cardiovascular Diseases

Tetralogy of Fallot (TOF)

Michael P. D'Alessandro, M.D.
Peer Review Status: Internally Peer Reviewed

Clinical Presentation:
The onset and degree of cyanosis depends on the severity of the pulmonary obstruction and the size of the shunt. Cyanosis is usually not seen until 3-6 months of age. The cyanosis is due to right ventricle outflow obstruction causing a right to left shunt of unoxygenated blood through the VSD into an overriding aorta and the systemic circulation. It is the most common cyanotic congenital heart defect.

Components include a large high VSD, pulmonary stenosis (usually infundibular), an overriding aorta which straddles the VSD, and right ventricular hypertrophy secondary to pulmonary outflow obstruction. The most severe form of TOF is pulmonary atresia associated with VSD, so called pseudotruncus. In pseudotruncus the pulmonary artery is not well developed and the entire pulmonary blood flow is through systemic or bronchial collaterals or a PDA.

Not applicable

Imaging Findings:
The heart is usually normal in appearance but right ventricular hypertrophy can produce an upturned cardiac apex. The pulmonary vascularity is decreased and the pulmonary trunk is small, causing a concavity along the left mid heart border. The upturned cardiac apex and the pulmonary artery concavity cause the appearance of a "boot shaped" heart which is usually seen in the older child or the patient with pseudotruncus. Other associated anomalies include mirror image right aortic arch in 25% of patients with TOF and 50% of patients with pseudotruncus, coronary artery anomalies, a persistent left superior vena cava , abnormalities of the pulmonary arteries, absent pulmonary valve, aortic insufficiency, and ASD.


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