Tetralogy of Fallot is the most common cause of blue baby syndrome in newborns. Babies are "blue" due to the cyanosis experienced in this heart disorder. This cyanosis directly correlates to the level of pulmonary stenosis, which prevents blood flow to enter the lungs from the right ventricle and forces deoxygenated blood through a VSD and into the systemic circulation.
Neonates often become cyanotic during times of feeding or crying when oxygen demand is greater than supply. These babies are sometimes termed “blue babies.”
One of the tetralogies which can occur is pulmonary infundibular stenosis. Stenosis is another term for narrowing. In ToF the outflow tract of the right ventricle is narrowed. The degree of cyanosis is directly correlated to the severity of narrowing.
Increased pressure caused by the narrowed outflow tract (pulmonary stenosis) causes a compensatory increase inside of the right ventricle. This often causes a boot shaped heart in the neonate on diagnostic exams.
In Tetralogy of Fallot, the aorta is shifted slightly to the right anteriorly to be on top of the VSD (ventricular septal defect). This causes the aorta to receive blood flow from both the right and left ventricle allowing deoxygenated blood to circulate throughout the body.
A defect/hole in the wall of the ventricles allows blood to shift between the ventricles. As pressures change between the left and right ventricle, deoxygenated blood can bypass the lungs and shunt into the left ventricle allowing deoxygenated blood to enter the systemic circulation.
Due to right ventricular hypertrophy (RVH), patients show a "boot-shaped" heart on X-ray.
Cyanotic episodes are termed “tet spells” and classically children will squat to relieve the cyanosis. Squatting increases the systemic vascular resistance, which decreases the amount of blood that crosses improperly through the VSD. This allows more blood flow to properly flow through the lungs.
The only definitive treatment for Tetralogy of Fallot is surgical treatment to correct the heart malformations.
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