What is Tetralogy of Fallot?

Treament is surgery to redirect the blood flow inside the heart so that it goes in the proper direction. What the surgical team will do during a 6 - 8 hour procedure. Genevieve's repairs are in red.

Ventricular Septal Defect or VSD
This hole permits blood to flow from the high pressure (red, oxygen carrying) left-sided circulation to the lower pressure (blue, oxygen poor) right-sided circulation. This abnormal blood flow is called a left-to-right shunt and follows this path because the left ventricle usually has a much higher pressure than the right ventricle.
Infundibular Stenosis
The infundibulum is in the outflow area (exit) of the right ventricle just beneath the pulmonary artery and valve. It forms a passageway for deoxygenated (blue) blood to flow to the lungs. Infundibular "stenosis" or narrowing means that there is a narrowing in this passageway that obstructs the flow of blood to the lungs. The degree of obstruction can range from mild to severe. This will cause the pressure inside the right ventricle to go up as it tries to push the blood through the area of obstruction. An added problem is that the pulmonary valve itself and the pulmonary artery may also be narrowed, which further adds to the obstruction.
Overriding Aorta
The aorta is the artery that carries oxygen rich red blood to the rest of the body and is normally open only to the left ventricle. In tetralogy of Fallot the aorta is shifted toward the right ventricle and sits above or "straddles" the VSD. The aorta is then open to both the right and left ventricle. This allows mixing of deoxygenated (blue) and oxygenated (red) blood as it flows out of the heart to the rest of the body. Thus the amount of oxygen in the circulation is lower than normal causing symptoms of shortness of breath, fatigue and a decreased activity level.
Right Ventricular Hypertrophy
Hypertrophy is a term used to describe a muscle that is unusually thickened. In tetralogy of Fallot, the right ventricular muscle wall is thickened because the right ventricle must work harder to push blood through the narrowed pulmonary artery and infundibulum. Unfortunately an increase in heart muscle thickness may precipitate irregular heart rhythms or cause patchy areas of scar tissue making the heart very "irritable." This makes the heart prone to irregular heart rhythms and reduced performance.

~information and diagram from The Mayo Clinic