Tetralogy of Fallot

Signs and Symptoms

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

Babies with tetralogy are blue at birth or soon after, and have detectable heart murmurs, an extra sound in the heartbeat. Activity such as crying may exacerbate the condition and babies may have shortness of breath or faint. Babies also may experience a "tetralogy spell" in which oxygen levels drop suddenly leading to irritability and then sleepiness or unresponsiveness. Giving oxygen to a baby with tetralogy usually doesn't improve blood oxygen levels.

Diagnosis

A complete circulation evaluation for tetralogy will include:

• Echocardiography, in which a picture is made of the heart by using sound waves.
• Chest X-ray
• Examination of the oxygen content of arterial blood. This is usually done with an oximeter, a little light that can be placed on a finger. Sometimes, a blood sample may be drawn from an artery in the wrist and checked for oxygen, carbon dioxide and acidity levels.

Treatment

Placing the baby on the stomach with the knees bent (in the "fetal position") may control a "tetrology spell." Newborns may be given a drug called prostaglandin to keep the ductus arteriosus, a part of the fetal circulation system, open to improve blood flow.

The defects usually are corrected during a single operation done when the baby is about 6 months old unless the baby has inadequate oxygen. If the baby is too small, there may be two surgical procedures.

The first procedure connects the pulmonary arteries to the aorta or its branches by a tube called a shunt to supply blood to the lungs. Later surgery enlarges the pulmonary valve opening and closes the ventricular septal defect (VSD) with a patch so that blood flows easily into the pulmonary artery and lungs. The shunt is then removed.