Tetralogy of Fallot is a congenital heart disease characterized by the presence of four fundamental cardiac abnormalities within the heart. These four findings are:

1. Ventricular Septal Defect (VSD): A large hole between the right and left ventricles, the lower chambers of the heart.
2. Right Ventricular Outflow Tract Obstruction (Pulmonary Stenosis): A narrowing of the pulmonary artery or pulmonary valve that carries blood from the right ventricle to the lungs, which restricts blood flow to the lungs.
3. Right Ventricular Hypertrophy: Thickening of the muscle walls of the right ventricle due to it working harder to overcome the resistance caused by pulmonary stenosis.
4. Overriding Aorta: The aorta, instead of originating solely from the left ventricle, is positioned directly over the ventricular septal defect, receiving blood from both ventricles.

The presence of these four findings together is necessary for the diagnosis of Tetralogy of Fallot.