Tetralogy of Fallot is the most common congenital heart defect. The word "tetralogy"
means a group of four, and in tetralogy of Fallot, there are four heart defects
that occur in combination:
- Ventricular septal defect (a hole in the wall of the heart [septum])
- Pulmonary valve stenosis (a narrowed or completely blocked pulmonary
valve, which restricts blood flow from the valve to the lungs)
- Malposition of the aorta (the aorta lies directly above the ventricular
septal defect, as opposed to a normal heart, in which the aorta stems from
the left ventricle)
- Right ventricular hypertrophy (when the pulmonary valve is narrowed or
blocked, it restricts blood flow out of the ventricle, causing it to
thicken)
What are the effects of tetralogy of Fallot?
In a case of tetralogy of Fallot, blood flow to the lungs and the body is
affected. Normally, the left ventricle pumps blood to the body and the right
ventricle pumps it to the lungs. In tetralogy of Fallot, blood may flow across
the ventricular septal defect (hole), from the right ventricle to the left
ventricle, where it is pumped to the rest of the body. The blood pumped to the
body lacks all of the oxygen it needs for organs to function properly.
The narrowed or obstructed pulmonary valve also limits the blood flow to the
lungs. With pulmonary valve narrowing or blockage, the blood pumped to the lungs
is low in oxygen because it is shunted through the ventricular septal defect,
from the right ventricle to the left ventricle.
Because the blood pumped to the body has less oxygen than it needs, one of
the symptoms of tetralogy of Fallot is a bluish tint to the skin, called
cyanosis. Periodically, infants with tetrology of Fallot can develop "tet
spells." During a tet spell, the infant develops rapid, deep breathing,
increased irritability, and prolonged crying, which in turn causes more intense
cyanosis. Tet spells require immediate attention to calm the baby and "break"
the spell. Emergency medical attention is required if the tet spell persists.
How are the heart defects corrected in tetralogy of Fallot?
Cardiac surgeons perform an open heart surgery during a child’s first year to
treat tetralogy of Fallot. The goal is to eliminate the shunting of blood across
the ventricles and to improve blood flow to the lungs.
A traditional procedure involves closing the ventricular septal defect and
placing a transannular patch (a patch across the pulmonary valve connective
tissue) to enlarge the pulmonary annulus (the ring of tissue that supports the
valve leaflets), which helps blood flow from the pulmonary valve. Closure of the
hole allows blood to flow to the lungs, where it picks up oxygen before it’s
pumped out into the body. The narrowing in the pulmonary valve is also repaired
with the transannular patch to improve blood flow to the lungs.