Tetralogy of Fallot
- Tetralogy of Fallot is caused by a single architectural defect in cardiac development that results in a combination of the four cardiac pathologies listed below
- 1) Ventricular Septal Defect (VSD)
- 2) Overriding Aorta: Aorta overrides the VSD resulting in the aorta receiving blood from both the right and left ventricle
- 3) Pulmonic Valve Stenosis: Stenosis in reality occurs below the pulmonic valve but often occurs together with congenital pulmonic valve stenosis
- 4) Concentric Right Ventricular Hypertrophy: Largely due to increased resistance to right ventricular outflow from the pulmonic stenosis
- Stenosis of the pulmonic valve increases the resistance of right ventricular blood flow into the pulmonary circulation. Consequently, much of the right ventricular blood is pumped through the VSD and directly into the aorta. The result is right-left shunting of blood which yields hypoxemia and cyanosis after birth. Clinical severity is largely dependent on the extent of pulmonic stenosis, and in milder cases Tetrology of Fallot can essentially mimic an isolated VSD. A systolic heart murmur is often heard, representing turbulent flow through the stenosed pulmonic outflow tract.