Tetralogy of Fallot

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

About 20% of cases of tetralogy of Fallot are associated with a chromosome 22q11 microdeletion or duplication.

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.

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