First described by Niels Stensen in 1672.

First correlation between pathology and clinical features by Fallot in 1888.

First aortopulmonary shunt by Blalock, Taussig and Thomas in 1945.

First intracardiac repair by Lillihei.


Tetralogy of Fallot is one of the most common cyanotic congenital heart diseases, by some series it is the commonest eg the BWIS study.

The prevalence of tetralogy of Fallot is 0.33 per 1000 live births.

Some studies have shown slight male preponderance in TOF eg BWIS study.


The sibling recurrence rate is 3%.

The chance of getting tetralogy of Fallot if a parent has tetralogy of Fallot is higher and is in the range of 1 to 8%. The chance may be higher if the affected parent is the mother.

Environmental factors

These include maternal diabetes, maternal phenylketonuria and maternal intake of retinoic acid, trimethadione or paramethadione.

Chromosomal anomalies

Some form of extracardiac anomaly is present in one-third of tetralogy of Fallot.

The most important syndromes associated with tetralogy of Fallot are Catch 22 and Alagille syndrome.

Catch 22 syndrome is characterized also by truncus arteriosus and interrupted aortic arch type B. The extracardiac anomalies are distinct facies, palatal anomalies, speech defects, learning defects, psychiatric defects, hypocalcemia and immunodeficiency. Earlier terms used for the syndrome were DiGeorge syndrome and velocardiofacial or Shprintzen syndrome. It is due to 22q11 deletion.

Alagille syndrome is characterized also by peripheral pulmonic stenoses. The extracardiac features are typical facies, ocular defects, skeletal defects and bile duct paucity. The defective gene is Jagged 1. The defect is inherited as autosomal dominant.


The conotruncus refers to the bulbus cordis and the truncus arteriosus together. It gives rise to the ventricular outflow tracts and the great arteries. It is divided into two by ingrowth of the truncal-bulbar ridges. It also undergoes a rotation. The conotruncal septum joins with the trabecular ventricular septum. There is a defect between these two that is closed by the membranous septum.

Tetralogy of Fallot is caused by malrotation of the truncal-bulbar ridges. This causes malalignment between the conotrunal septum and the trabecular septum.