Newborn Diagnosis: Tetralogy of Fallot

Tetralogy of Fallot

Tetralogy of Fallot is a congenital heart defect, which affects the heart’s structure, causing blood with low levels of oxygen to circulate throughout the body. Babies born with tetralogy of Fallot tend to have a blue discoloration of the skin due to low oxygen levels in their blood.

This congenital heart defect is often diagnosed soon after birth or during infancy. However, in some people, the condition might go undetected until they reach adulthood.

Most children and adults who are early diagnosed and treated with surgery relatively live a normal life, although long-term medical care with some restrictions on exercise may be required.

Symptoms

The symptoms of tetralogy of Fallot usually vary and depend on the severity of blood flow obstruction out of the heart’s right ventricle into the lungs. Some of its common signs and symptoms are:

• Cyanosis (bluish or purplish skin discoloration due to low oxygen levels in the blood)
• Breathing problems (particularly during exercise or feeding)
• Fainting (temporary loss of consciousness)
• Clubbing of the fingers or toes
• Slow weight gain
• Tiredness during exercise or play
• Irritability
• Excessive crying
• Heart murmurs

When to Call for Help

Seek immediate medical help if you notice any of the following symptoms in your child:

• Breathing difficulty
• Bluish or purplish discoloration of the skin
• Irritable mood
• Fainting
• Seizures
• Weakness

Immediately call 911 or your local emergency number. If your child turns bluish, place your child on his or her side and then pull your child’s knees up to his or her chest to help increase the flow of blood to the lungs. 

Causes

Tetralogy of Fallot usually occurs in a baby’s developing heart during fetal growth. Most cases of this congenital heart defect have unknown causes, although factors such as viral disease, genetic disorders, and poor maternal nutrition may contribute to the condition. Tetralogy of Fallot consists of four heart defects. They are:

• Pulmonary Valve Stenosis (PVS) – This is a heart valve disorder, characterized by an obstruction of blood outflow from the heart’s right ventricle at the pulmonic valve level. PVS usually results in blood flow reduction to the lungs.

• Ventricular Septal Defect (VSD) – VSD is a heart defect or hole in the septum that separates the two lower chambers of the heart, which are the right and left ventricles. Normally, the septum or wall between the heart’s chambers closes before a child is born to prevent the mixing of oxygen-rich blood with the oxygen-poor blood at birth. A reduced oxygen level in the body may occur and when the hole does not close. This defect can cause the heart to become weak.

• Overriding Aorta – This is another congenital heart defect, in which the aorta (the main artery in the body), is situated directly above a ventricular septal defect rather than being positioned over the left ventricle. This defect results in the aorta receiving blood from the right ventricle, which reduces the level of oxygen in the blood.

• Right Ventricular Hypertrophy (RVH) – It is a form of ventricular hypertrophy that affects the right ventricle. When the pumping action of the heart is overworked, the muscular wall of the right ventricle thickens, which eventually causes the heart to stiffen and become weak and fail over time.

Diagnosis 

Doctors might suspect tetralogy of Fallot in babies if they notice a bluish skin discoloration or heart murmurs. A pediatric cardiologist will physically examine your child along with using several tests to arrive at an accurate diagnosis. Tests may include any of the following:

1. Echocardiography

An echocardiogram produces high-pitched sound waves to produce images of the heart. This test allows doctors to visualize the heart beating and pumping blood, as well as to identify heart diseases.  

Generally, an echocardiogram is used to diagnose tetralogy of Fallot. Doctors make use of this test to help identify the following:

• A ventricular septal defect and its location
• Check the structure of the pulmonary artery and pulmonary valve
• Check the functioning of the right ventricle
• Check if the aorta is properly positioned
• Other heart defects

2. Electrocardiogram (EKG or ECG)

An electrocardiogram (EKG or ECG) is a test that can help record the heart's electrical activity. In this procedure, electrodes are placed on your child's chest, ankles, and wrists. These electrodes measure the electrical activity of the heart, which is simultaneously recorded on paper. An ECG can help determine the presence of an enlarged right ventricle, an enlarged right atrium, and irregular heart rhythm. 

3. Chest X-Ray

A chest X-ray can produce images of the heart and lungs. When it comes to tetralogy of Fallot, one common sign is a "boot-shaped" heart on a chest X-ray due to the enlargement of the right ventricle. 

4. Pulse Oximetry (Oxygen Level Measurement)

Pulse oximetry is a method of measuring the blood's oxygenation level. This test makes use of a small sensor that is placed on a finger or toe. A pulse oximeter can rapidly detect the changes in a person's blood oxygen level. 

5. Cardiac Catheterization 

Cardiac catheterization is a test used to help evaluate the heart’s structure and when planning for a surgical treatment. In this procedure, doctors insert a catheter (thin and flexible tube) into your baby’s vein or artery in the arm, neck, or groin, and then threads it up to your baby’s heart. A dye is injected through the catheter to visualize your baby’s heart structures on an X-ray. Cardiac catheterization can also help measure the oxygen levels and pressure in the heart’s chambers and blood vessels. 

Diagnosis and Management During Pregnancy

If a fetal heart defect is suspected after reviewing the routine ultrasound, then the doctor can order for a fetal echocardiogram. This procedure is safe and noninvasive. It shows the structure and the working of the heart. Thus, a diagnosis of tetralogy of Fallot during pregnancy is possible, and after delivery, the doctor can discuss possible options.

For the remainder of the pregnancy, the baby is closely monitored by a fetal heart team. If the baby has tetralogy of Fallot before birth, the baby can still be delivered vaginally unless otherwise instructed by the obstetrician. It is best for these babies to be delivered at medical centers since a team of experts, such as neonatologists and pediatric cardiologists can help monitor the babies. There would also be access to neonatal intensive care unit when the baby is born.