Tetralogy of Fallot
The “Skeleton” of the heart is the cartilaginous, fibro-muscular part of the heart that gives it structure and integrity. It is composed of the aorto-pulmonary or semilunar apparatus that gives rise to the aortic and pulmonary valves, the endocardial cushions that give rise to the mitral and tricuspid valves, and the inter atrial and inter ventricular septa. This structure forms in the early weeks of fetal development moving inward towards the center, eventually forming a “cross” like or “t” shaped fully functional apparatus, which separates the four chambers and houses all four valves of the heart.
The center of this “t” shaped apparatus is known as the “crux” of the heart. Tetralogy of Fallot is one of the most common complex defects and occurs when the aorto-pulmonary apparatus and the inter ventricular septum fails to form appropriately at the crux, leaving a large membranous VSD, a stenosed and improperly formed infundibulum (right ventricular outflow tract) and a stenosed or even atretic (absent or fused) pulmonic valve. Additionally, the aorta is deviated anteriorly (as a result of the malformed infundibulum) so that it overrides the ventricular septum, and right ventricular hypertrophy.
Hence, the name “tetra” meaning four, so Tetralogy of Fallot are four defects, previously mentioned.
Surgical Repair consists of patch repair of the VSD, reconstruction of the stenosed pulmonic valve and removal of any previously implanted shunts (Blalock-Taussig shunt). The surgery used to be a two-stage process but it now is usually done as one procedure at about six months of age. Surgical outcomes are very good, with less than a 5% mortality rate.
Ken Heiden