Tetralogy of Fallot: Nursing

Tetralogy of Fallot, or ToF, is the most common congenital heart defect. Similarly to pulmonary stenosis, the cause of ToF is unknown, but genetic factors likely play a role in its development. ToF consists of four different defects.

These defects include pulmonary stenosis, right-ventricular hypertrophy, VSD and an overriding aorta, which happens when the aorta is displaced and blood from both sides of the heart is able to flow through it.

In some clients a fifth defect, ASD, may be present. Since all of these factors can lead to right to left shunting of blood, ToF can also be classified as a cyanotic heart condition.

Now, the direction of the shunting in ToF isn’t always right to left. In this condition, it depends on the severity of the obstructive defects and the pressure difference between pulmonary vascular resistance and systemic resistance.

Pulmonary vascular resistance is the amount of force exerted against blood flow from the pulmonary artery to the left atrium; and systemic resistance is the amount of force exerted on circulating blood by the vasculature of the body.

So if the pulmonary vascular resistance is greater than systemic resistance, blood will shunt from right to left.

But, if the systemic resistance is greater than pulmonary vascular resistance, blood will shunt from left to right.

In this situation, excess oxygenated blood from the left ventricle will shunt over to the right ventricle through that VSD.

These clients are at risk for developing pulmonary congestion since all this extra blood volume shunting over to the right side will make its way to lungs.

Now, symptoms can vary broadly in different clients, some with just mild symptoms, while others can have a much more severe experience. The wide difference in symptoms is directly related to how much blood gets oxygenated.

These symptoms of ToF can be present at birth, and the infant may appear cyanotic, like in right to left shunting scenarios; or acyanotic, like in left to right shunting scenarios. These are sometimes referred to as “blue baby syndrome” and "pink baby syndrome".

In other cases, cyanosis may be less acute initially, but can progress over the first 12 months of life; specifically as the pulmonary stenosis defect worsens.

Another common initial finding in infants with ToF is a characteristic loud and harsh heart murmur.

Now, with a right to left shunting of blood, the body’s demand for oxygen exceeds what’s available in the blood supply, since less blood reaches the lungs.

When this occurs, infants and children can experience hypercyanotic spells, called “blue spells” or “tet spells”.

These spells can be particularly worrisome to parents, guardians or caregivers of the child during this time because they can become extremely cyanotic and appear to be starving for air.

In more severe cases, the child may pass out, lose consciousness or even experience convulsions. Episodes like this can last anywhere from a few minutes to a few hours.

This is a very exhausting experience for a child, so muscle weakness and a long period of sleep can be expected afterwards.

Actions like crying, feeding or having a bowel movement are common causes of these spells, because these actions increase the body’s demand for oxygen.