Tetralogy of Fallot

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

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 and right-to-left shunt at the VSD due to severe RVOT obstruction (“blue tet”) to moderate pulmonary overcirculation and left-to-right shunt at the VSD with minimal RVOTO (“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.