Tetralogy of Fallot (TOF) with pulmonary stenosis is the common form of tetralogy of Fallot, and it is the focus of this article.
Tetralogy of Fallot is a conotruncal defect resulting from anterior malalignment of the infundibular septum. This single morphologic defect gives rise to the 4 main components of Tetralogy of Fallot: (1) ventricular septal defect (VSD), (2) aortic valve overriding the ventricular septum, (3) narrowing of the right ventricular (RV) outflow tract (RVOT), and (4) RV hypertrophy (RVH).
A uniform etiology may explain this anatomic tetrad. That is, the monology of anterior deviation of the infundibular septum causes hypoplasia of the subpulmonary infundibulum and thus accounts for all components of the tetrad.
Tetralogy of Fallot is the most common cyanotic heart defect seen in children beyond infancy and occurs in 10% of all congenital defects. Furthermore, tetralogy of Fallot is the most common cyanotic congenital lesion that is likely to result in survival to adulthood. It is also the most common complex lesion to be encountered in the adult population after repair. Environmental associations with tetralogy of Fallot include maternal diabetes mellitus, retinoic acid exposure, and maternal phenylketonuria (PKU). This defect has a frequent association with the 22q11 chromosomal deletion and can also be seen associated with trisomy 21, 18, or 13. Other possible genetic associations are currently an ongoing area of active research.
Complex forms include tetralogy of Fallot with absent pulmonary valve and tetralogy of Fallot with pulmonary atresia with or without major aortopulmonary collateral arteries (MAPCAs).
Tetralogy of Fallot holds a central place in the history of surgery for congenital heart disease; it was the first cyanotic cardiac lesion to be successfully managed with surgical palliation and was one of the first cardiac lesions to undergo successful intracardiac repair.
The classic Blalock-Taussig (BT) shunt procedure developed in 1945 involved direct end-to-end anastomosis between the subclavian artery and the pulmonary artery. This technique required transection of the subclavian artery. Professor Marc deLeval modified this procedure using an interposition conduit between subclavian artery and pulmonary artery. This modified BT shunt (also, deLeval shunt, Great Ormond Street [GOS] shunt), is currently the most commonly used systemic–to–pulmonary artery shunt.
Since the introduction of cardiopulmonary bypass, the trend has been for early and complete repair. The cardiopulmonary bypass machine is used to perform complete intracardiac repair of tetralogy of Fallot (see Corrective Surgery).