Tetralogy of Fallot

Tetralogy of Fallot (TOF) is a congenital heart defect consisting of four features: ventricular septal defect (VSD), right ventricular outflow tract obstruction, overriding aorta, and right ventricular hypertrophy. It is the most common type of cyanotic congenital heart disease.

TOF is classified based on whether the pulmonary valve is completely closed (pulmonary atresia), the size of the pulmonary arteries, and the presence of additional collateral arteries called MAPCAs.

The symptoms of TOF vary depending on the severity of the narrowing in the right ventricular outflow tract. If the narrowing is mild, there may be little or no cyanosis (pink TOF). In patients with cyanosis, it can worsen with increased activity or as the narrowing of the right ventricular outflow tract progresses.  In some cases, severe reduction in blood flow to the lungs can cause hypoxic spells