Tetralogy of Fallot

Tetralogy of Fallot

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Tetralogy of Fallot

Tetralogy of Fallot (pronounced te-tral-uh-jee of Fal-oh) is a birth defect that affects normal blood flow through the heart. It happens when a baby’s heart does not form correctly as the baby grows and develops in the mother’s womb during pregnancy.

Patients with tetralogy of Fallot have a VSD, RV infundibular stenosis, RVH, and a dilated aorta (in about 50% of patients it overrides the septum). If there is an associated ASD, the complex is referred to as pentalogy of Fallot. There may or may not be pulmonary valve stenosis as well, usually due to a bicuspid pulmonary valve or RV outflow hypoplasia. The aorta can be quite enlarged and aortic regurgitation may occur. If more than 50% of the aorta overrides into the RV outflow tract, the anatomy is referred to as a “double outlet RV.”

Two vascular abnormalities are common: a right-sided aortic arch (in 25%) and an anomalous left anterior descending coronary artery from the right cusp (7–9%). The latter is important in that surgical correction must avoid injuring the coronary artery when repairing the RV outflow obstruction. Pulmonary branch stenosis may also be present.

Most adult patients have undergone prior surgery. If significant RV outflow obstruction is present in the neonatal period, a systemic arterial to pulmonary artery shunt may be the initial surgical procedure to improve pulmonary blood flow, though many infants undergo repair without this first step. Most adults will have had this initial palliative repair, however. The palliative procedure enables blood to reach the underperfused lung either by directly attaching one of the subclavian arteries to a main PA branch (classic Blalock shunt) or by creating a conduit between the two (modified Blalock shunt).

In the adult, there may be a reduced upper extremity pulse on the side used for the classic Blalock procedure. Total repair of the tetralogy of Fallot generally includes a VSD patch and usually an enlarging RV outflow tract patch, as well as a takedown of any prior arterial-pulmonary artery shunt. Often the RV outflow tract patch extends through the pulmonary valve into the PA (transannular patch), and the patient then is left with varying degrees of pulmonary valve regurgitation (although great effort is made to avoid pulmonary valve regurgitation if at all possible).

Over the years, the volume overload from severe pulmonary valve regurgitation becomes the major hemodynamic problem seen in adults. Ventricular arrhythmias can also originate from the edge of the patch and tend to increase in frequency as the size of the RV increases.

Causes and Risk Factors

The causes of heart defects (such as tetralogy of Fallot) among most babies are unknown. Some babies have heart defects because of changes in their genes or chromosomes. Heart defects such as tetralogy of Fallot also are thought to be caused by a combination of genes and other risk factors, such as the things the mother or fetus come in contact with in the environment or what the mother eats or drinks or the medicines she uses.

Signs and symptoms

Most adult patients in whom tetralogy of Fallot has been repaired are relatively asymptomatic unless right heart failure occurs or arrhythmias become an issue. Patients can be active and generally require no specific therapy.

Physical examination should include checking both arms for any loss of pulse from a prior shunt procedure in infancy. The jugular venous pulsations (JVP) may reveal an increased a

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wave from poor RV compliance or rarely a c-v wave due to tricuspid regurgitation. The right-sided arch has no consequence. The precordium may be active, often with a persistent pulmonary outflow murmur. P2may or may not be audible. A right-sided gallop may be heard. A residual VSD or an aortic regurgitation murmur may be present. At times, the insertion site of a prior Blalock or other shunt may create a stenotic area in the branch PA and a continuous murmur occurs as a result.

Diagnosis

During Pregnancy

During pregnancy, there are screening tests (also called prenatal tests) to check for birth defects and other conditions. Tetralogy of Fallot might be seen during an ultrasound (which creates pictures of the body). Some findings from the ultrasound may make the health care provider suspect a baby may have tetralogy of Fallot. If so, the health care provider can request a fetal echocardiogram to confirm the diagnosis. A fetal echocardiogram is an ultrasound of the heart of the fetus. This test can show problems with the structure of the heart and how the heart is working with this defect.

After a Baby Is Born

Tetralogy of Fallot usually is diagnosed after a baby is born, often after the infant has an episode of turning blue during crying or feeding (a tet spell). Some findings on a physical exam may make the health care provider think a baby may have tetralogy of Fallot, including bluish-looking skin or a heart murmur (a “whooshing” sound caused by blood not flowing properly through the heart). However, it is not uncommon for a heart murmur to be absent right at birth.

The health care provider can request one or more tests to confirm the diagnosis. The most common test is an echocardiogram. An echocardiogram is an ultrasound of the heart that can show problems with the structure of the heart and how the heart is working (or not) with this defect. Echocardiography also is useful for helping the doctor follow the child’s health over time.

Tetralogy of Fallot is a critical congenital heart defect (critical CHD)that may be detected with newborn screening using pulse oximetry(also known as pulse ox). Pulse oximetry is a simple bedside test to estimate the amount of oxygen in a baby’s blood. Low levels of oxygen in the blood can be a sign of a critical CHD. Newborn screening using pulse oximetry can identify some infants with a critical CHD, like tetralogy of Fallot, before they show any symptoms.

Treatments

Tetralogy of Fallot can be treated by surgery soon after the baby is born. During surgery, doctors widen or replace the pulmonary valve and enlarge the passage to the pulmonary artery. They also will place a patch over the ventricular septal defect to close the hole between the two lower chambers of the heart. These actions will improve blood flow to the lungs and the rest of the body.

Most infants will live active, healthy lives after surgery. However, they will need regular follow-up visits with a cardiologist (a heart doctor) to monitor their progress and check for other health conditions that might develop as they get older. As adults, they may need more surgery or medical care for other possible problems.

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