Tetralogy of Fallot (ToF)
Tetralogy of Fallot (ToF): “Tetra” means “four”; therefore, there are four defects that make up this form of heart disease. Due to abnormal closure of the ventricular septum in the fetus, the patient is left with a ventricle septal defect (VSD), an over-riding aorta (where the aorta lives over the ventricular septum), pulmonary stenosis (PS), and a thick, muscle-bound right ventricle due to all the work created pumping against the tight pulmonic valve (PV).
Blue blood returns to the right heart as usual, but has some difficulty getting out to the pulmonary arteries, depending on the tightness or narrowness of the pulmonary valve, and the area underneath the pulmonary valve. The degree to which the patient appears blue depends upon how much blood can get out to the lungs to pick up oxygen. Some of the blue blood can get pushed across the VSD into the left ventricle (LV) and circulated out to the rest of the body.
The red or oxygen-rich blood returns to the left atrium (LA), goes to the LV and is pumped out to the aorta. If the PS is not too severe, some of the red blood can be pushed across the VSD and pumped back into the PA s.
Patients with ToF may never look blue, however some patients can have “tet” spells or hypercyanotic spells. These seem to occur in patients with the thickest, most muscular, narrowest right hearts. The muscle clamps down beneath the pulmonary valve and blood cannot get out into the lungs. The patient appears dark blue, gray, or pale and is often very distressed or (worse) unresponsive. This is an emergency, and parents may push the patients knees to the chest and keep the patient quiet until emergency helps arrives.
