Tetralogy of Fallot is a combination of four heart defects that can result in a baby turning blue or cyanotic because of a lack of oxygen in the blood.
The heart consists of four chambers — the two upper chambers, called atria, where blood enters the heart, and the two lower chambers, called ventricles, where blood is pumped out of the heart. The flow between the chambers is controlled by a set of valves that act as one-way doors.
Normally blood is pumped from the right side of the heart through the pulmonary valve and the pulmonary artery to the lungs, where the blood is filled with oxygen. From the lungs, the blood travels back down to the left atrium and left ventricle. The newly oxygenated blood then is pumped through another big blood vessel called the aorta to the rest of the body.
The four defects characteristic of this condition include:
-
An abnormal opening in the wall separating the ventricles called a ventricular septal defect (VSD) that allows blood to go directly from the right to left ventricle without going through the lungs
-
A narrowing below the pulmonary valve called pulmonary artery stenosis that partially blocks blood flow to the lungs
-
An overly muscular right ventricle, also called right ventricular hypertrophy
-
A displaced aorta, also called overriding aorta, directly over the abnormal opening between the ventricles