What is Tetralogy of Fallot?

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  • Written By: wiseGEEK Writer
  • Edited By: Niki Foster
  • Last Modified Date: 14 July 2019
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Tetralogy of Fallot (TOF) is a group of four congenital heart defects necessitating treatment during the first few months of life because they cause cyanosis, blueness resulting from the body receiving oxygen-poor blood. Tetralogy of Fallot is the most common combination heart defect resulting in cyanosis. One case is present in about every 2000-3000 births.

Two of the four defects present in Tetralogy of Fallot create the greatest issue for the newborn. These are large ventricular septal defects and significant pulmonary stenosis. In some cases, TOF presents with pulmonary atresia, which generally requires immediate surgical attention after a child is born because no blood can pass through the pulmonary valve to get necessary oxygen from the lungs.

Children born with this variant of Tetralogy of Fallot tend to go into heart failure soon after birth. Doctors can delay this failure through the intravenous administration of Prostaglandin E, a medication that delays the small opening in the atria, the patent ductus, from closing. This offers only a day or two of support before surgery must be performed.


The other two defects in Tetralogy of Fallot create fewer problems. Children with TOF have an overriding aorta, which means that the ventricular septal defect is below the aorta, allowing both oxygen-poor and oxygen-rich blood to be pumped back into the body. The right ventricle is also thick and enlarged as a result of higher pressure in the ventricle, caused by blood mixing through the ventricular septal defect.

Uncomplicated Tetralogy of Fallot is often repaired in one surgery, generally before the child’s first birthday. Most surgeons favor early repair, because children who remain untreated exhibit poor growth and difficulty feeding. Additionally, the pressure on the right ventricle can continue to rise and create further thickness, also known as hypertrophy.

Children with unrepaired TOF also exhibit “tet spells,” in which they can turn mostly blue for a few seconds to a few minutes. Tet spells can be induced by excessive crying or can occur with no warning. They are naturally alarming to parents and other caregivers.

Single surgery repair of Tetralogy of Fallot is an open-heart procedure. Open heart surgery implies that the child will be on heart lung bypass for a period of time while the repair takes place. In this repair of TOF, children are generally on bypass for under an hour.

In a single surgery, the ventricular septal defect is repaired, and where possible, the pulmonary valve is opened with balloon valvuloplasty. The surgeon may elect to open the valve, place a patch on it to create a wider opening and then stitch the valve. Patching the valve is preferable to valve replacement.

Patched valves can sometimes become leaky over time and necessitate additional surgery or replacement. In Tetralogy of Fallot with pulmonary atresia, the valve generally must be replaced during surgery. Some surgeons prefer to perform two surgeries to address TOF with pulmonary atresia: one to replace the pulmonary valve, and one to repair the ventricular septal defect.

Children born with Tetralogy of Fallot require lifetime follow-up visits with a cardiologist, who will most particularly look at the degree to which the pulmonary valve is working. They may also require daily low dose aspirin, and will definitely need to take prophylactic antibiotics prior to dental work. Cardiologists may place some limitations on participation in sports, but most children are encouraged to do as much as they can. Survival rates for open-heart surgeries are between 90-95%. Hence, those born with Tetralogy of Fallot can be reasonably expected to do well long-term and to live healthy, normal lives.



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