Fallot's tetrad: what is it, symptoms, treatment, prognosis

What is Fallot's tetrad?

Fallot's tetrad - the most common form of cyanotic (cyanotic) congenital heart disease. Cyanosis is a bluish-cyanotic discoloration of the skin resulting from low levels of circulating oxygen in the blood. Fallot's tetralogy consists of a combination of four different heart defects: ventricular septal defect (VSD); obstructed outflow of blood from the right ventricle to the lungs (pulmonary artery stenosis); a displaced aorta causing blood to flow into the aorta from both the right and left ventricles (aortic dextraposition); and abnormal enlargement of the right ventricle (right ventricular hypertrophy). The severity of symptoms is associated with the degree of obstruction of blood flow from the right ventricle.

Introduction

A normal heart has four chambers. The two upper chambers, known as the atria, are separated from each other by a fibrous septum known as the atrial septum. The two lower chambers are known as the ventricles and are separated from each other by an interventricular septum. The valves connect the atria (left and right) to the corresponding ventricles. The valves allow blood to be pumped through the chambers. Blood moves from the right ventricle through the pulmonary artery to the lungs, where it receives oxygen. Blood returns to the heart through the pulmonary veins and enters the left ventricle. The left ventricle now sends oxygenated blood to the body's main artery (aorta). The aorta carries blood through the body.

—​ Ventricular septal defect.

The heart has an inner wall that separates the two chambers, called a septum. The septum prevents blood from mixing between the two sides. A ventricular septal defect is an opening in the septum that causes oxygen-rich blood (left ventricle) and oxygen-poor blood (right ventricle) to mix.

- Pulmonary stenosis.

This defect is a narrowing of the pulmonary valve, through which blood with low oxygen content enters the pulmonary artery, and from there blood enters the lungs to take oxygen. Pulmonary stenosis is when a pulmonary valve fails to open fully, causing the heart to work harder and causing a lack of blood to reach the lungs.

— Right ventricular hypertrophy.

With hypertrophy, the muscle of the right ventricle is thicker due to the fact that the right side of the heart receives excessive blood flow from the left side of the heart through the ventricular septal defect and works more intensely.

— Dextraposition of the aorta.

In a normal heart, the aorta is attached to the left ventricle and allows oxygen-rich blood to flow throughout the body. In tetralogy of Fallot, the aorta of the heart is located between the left and right ventricles. This causes oxygen-poor blood from the right ventricle to flow into the aorta rather than the pulmonary artery. If left untreated, infants with tetrad of Fallot, symptoms usually become more severe. Blood flow to the lungs can be further reduced, and severe cyanosis can cause life-threatening complications.

Signs and symptoms

Symptoms of tetrad of Fallot vary widely from person to person. The severity of symptoms, which can range from mild to severe, is related to the degree of obstruction of blood flow from the right ventricle.

Fallot's tetralogy may be present at birth or appear during the first year of life. The most common sign of the disease is an abnormal change in skin color to a bluish tint (cyanosis). This can happen when the baby is at rest or crying. The mucous membranes of the lips and mouth, fingertips and toenails can be especially blue due to lack of oxygen. Affected infants may have difficulty breathing (dyspnea); as a result, they tend to play for short periods of time and then rest. Other symptoms may include:

• heart murmur;
• easy fatigue;
• lack of appetite;
• slow weight gain;
• an abnormal increase in the number of red blood cells (polycythemia);
• fingers and toes with wide, enlarged tips and hanging nails (Hippocrates' fingers);
• growth retardation.

Some babies with tetralogy of Fallot may have episodes of severe cyanosis and difficulty breathing (severe dyspnea-cyanotic attacks). During these seizures, the infant may become restless, extremely cyanotic, suffocate, and unresponsive to parental voices. In extreme situations, babies can faint. A characteristic squatting position can be adopted to facilitate breathing. Severe seizures can lead to loss of consciousness and sometimes to seizures or temporary paralysis of one side of the body (hemiparesis). These attacks can last from a few minutes to several hours and may be accompanied by periods of muscle weakness and prolonged periods of sleep.

In connection with Fallot's tetrad, a number of other complications may arise. They may include mild anemia in infants, an abnormal increase in the number of red blood cells (polycythemia) in older children, and blood clotting (coagulation) defects. These blood abnormalities can lead to blood clots (blood clots) that can travel with the bloodstream (embolism). These blood clots can cause temporary interruption of the blood supply to the brain (cerebral infarction).
Additional complications may include sinus infections (sinusitis) and brain abscesses. In some cases, the junction between the aorta and the pulmonary artery, which normally closes before birth, may remain open (patent ductus arteriosus). Symptoms associated with this condition vary depending on the size of the opening and may include rapid breathing, frequent respiratory infections, and easy fatigue. Stagnant heart failure is rare, except when it is associated with a bacterial heart infection (endocarditis) or heart rhythm disturbances (arrhythmias). However, a common symptom is a heart murmur or extra sound heard when listening to a heartbeat.

The most severe form is Fallot's tetrad with pulmonary atresia. Babies with this form of the disorder experience severe symptoms due to severe obstruction right ventricular blood flow and severe underdevelopment of associated blood vessels and valves associated with light. In this form of the disease, ventricular septal defects are usually severe. Severe cyanosis, alarmingly low circulating oxygen and excessive circulating red blood cells (polycythemia) are the main signs of tetralogy of Fallot with pulmonary atresia arteries.

Causes and risk factors

The exact cause of Fallot's tetrad is not known. However, some studies suggest that the disease may be due to the interaction of several genetic and / or environmental factors (multifactorial). Therefore, the researchers suspect that something could affect the genes of the developing fetus, causing this birth defect, but the exact nature of this trigger is unknown.

Some conditions that can increase your risk of having a baby with Fallot's tetralogy include:

• viral diseases;
• alcohol consumption;
• diabetes;
• poor nutrition;
• pregnancy over the age of 40.

Approximately 25 percent of babies with tetralogy of Fallot also have other birth defects that are not related to the function or structure of the heart.

Affected populations

Fallot's tetralogy is a rare congenital heart disease that is more common in men than women. About 1 percent of newborns have congenital heart defects. About 10 percent of these babies are diagnosed with tetrad of Fallot. This heart defect usually appears several weeks or months after birth. The prevalence of the disorder is estimated at 1 in 3000 live births.

Children with chromosomal abnormalities such as Down syndromeoften have tetrad of Fallot and other congenital heart defects.

Related disorders

Symptoms of the following diseases may be similar to those of Fallot's tetrad. Comparisons can be useful for differential diagnosis:

• Atrial septal defect (ASD) - common congenital heart defects, characterized by the presence of a small hole between the two atria of the heart. These defects lead to increased stress on the right side of the heart, as well as excessive blood flow to the lungs. Patients' symptoms vary greatly, and may manifest in infancy, childhood or adulthood, depending on the severity of the defect. Symptoms are usually mild at first and may include difficulty breathing (shortness of breath), increased sensitivity to respiratory infections and abnormal discoloration of the skin and / or mucous membranes to a bluish tinge (cyanosis). Some people with ASD may be at increased risk of blood clots, which can travel to the main arteries (embolism), blocking blood circulation.
• Ventricular septal defect (VSD) is a group of common congenital heart defects characterized by the absence of one ventricle. Babies with these defects may have 2 atria and 1 large ventricle. The symptoms of these conditions are similar to those of other congenital heart defects and may include abnormally rapid breathing (tachypnea), blue skin color (cyanosis), wheezing, heart palpitations (tachycardia) and / or abnormally increased liver (hepatomegaly). VSD can also cause excessive fluid buildup around the heart, leading to congestive heart failure.
• Atrioventricular canal defect (DAVK) is a rare heart disease that is present at birth (congenital) and is characterized by abnormal development of the septa and heart valves. Babies with complete malformation usually develop congestive heart failure. Excess fluid builds up in other parts of the body, especially the lungs. Lung congestion can lead to difficulty breathing (dyspnea). Other symptoms may include blue skin (cyanosis), malnutrition, rapid breathing (tachycardia) and heart rate (tachycardia), and / or excessive sweating (hyperhidrosis). Adults with DAVK may experience abnormally low blood pressure, irregular heartbeat, and / or rapid heartbeat.
• Three atrial heart - extremely rare congenital heart disease, characterized by the presence of an additional chamber above the left atrium of the heart. Pulmonary veins, returning blood from the lungs, drain into this additional "third atrium". The symptoms of the disease vary greatly and depend on the size of the opening between the chambers. Symptoms may include abnormally rapid breathing (tachypnea), blue skin (cyanosis), wheezing, coughing, and / or abnormal buildup fluid in the lungs.
• Double branching of great vessels from the right ventricle - extremely rare congenital heart disease, characterized by the absence of one ventricle. Babies with this defect have 2 atria and 1 large ventricle. Symptoms are similar to those of other congenital heart defects and may include shortness of breath (shortness of breath), excessive accumulation of fluid in and around the lungs (pulmonary edema) and / or blue discoloration of the skin and mucous membranes (cyanosis). Other symptoms may include malnutrition, abnormally rapid breathing (tachypnea), and / or rapid heartbeat (tachycardia).
• Mitral valve stenosis - a rare heart disease that may be present at birth (congenital) or acquired. It is characterized by abnormal narrowing of the mitral valve opening. In the congenital form, symptoms vary greatly and may include coughing, shortness of breath, heart palpitations, and / or frequent respiratory infections. With acquired mitral stenosis, symptoms may also include weakness, abdominal discomfort, chest pain (angina) and / or periodic loss of consciousness.

Diagnostics

The diagnosis of tetrad of Fallot is confirmed by clinical examination and physical examination. Various specialized tests, including electrocardiogram, echocardiogram, and cardiac catheterization, may be performed to aid diagnosis and therapy. When tetralogy of Fallot is present, x-rays usually reveal a normal-sized heart that has the characteristic "wooden shoe" shape. Periodic measurement of blood oxygen saturation and hemoglobin is also recommended. Babies with this condition usually have a relatively loud murmur in the upper left side of the sternum.

Standard treatments

The definitive treatment for tetralogy of Fallot is surgery (for example, bypass surgery Blaylock-Taussig, aortic / pulmonary bypass, intracardiac repair, balloon pulmonary valvuloplasty and / or valve replacement). Surgical correction of this heart defect is best done in infancy. The choice of the exact surgical procedure depends on the severity of the symptoms and the degree of the malformation.

The surgeon widens the pulmonary valve and the passage from the right ventricle to the pulmonary artery is enlarged. Next, the patch closes the hole in the septum to correct the defect of the interventricular septum. By solving problems with VSD and pulmonary valve, two other defects are eliminated.

If the infant is too weak or small to undergo a full reconstructive surgery, temporary surgery may be recommended; a full reconstructive operation will be performed when the child is strong. During temporary surgery, a tube or "shunt" is placed between the large artery branching from the aorta and the pulmonary artery. It creates a pathway for blood to travel to the lungs to receive oxygen. The tube is removed during a complete reconstructive surgery.

If early recovery is not possible, other surgical measures may be taken during infancy or early childhood.

Before surgery, treatment to control symptoms (palliative care) may include maintaining adequate fluid intake (hydration), monitoring hemoglobin levels in the blood, and avoiding any physical loads. Heart medications (such as digitalis) may be prescribed to control irregular heartbeats (arrhythmias), increased heart rate, and / or heart failure.

Episodes of severe symptoms or “blue periods” (hypoxia) may require supplemental oxygen, morphine, and / or other drugs that increase oxygen concentration. A knee-chest position can also relieve symptoms. Sodium bicarbonate can be given to lower abnormally high blood acid levels (acidosis). Propranolol may be prescribed to prevent future attacks and reduce their severity. Medications that help flush excess fluid from the body (diuretics), dietary salt restriction, and bed rest can be effective in treating congestive heart failure.

Babies with tetrad of Fallot may be prescribed antibiotics to prevent infections (prophylaxis), as babies with this condition are prone to a bacterial infection of the heart (endocarditis). Respiratory infections must be treated vigorously and early. Children should be given antibiotics at times of predictable risk (such as tooth extraction and surgery). Other treatments are symptomatic and supportive.

Although the risk of tetralogy of Fallot in siblings of infants with this condition is considered very low, genetic counseling can be beneficial for parents and other family members.

Forecast

Fallot's tetralogy is the most common type of cyanotic congenital heart disease. Since the first surgery in 1954, the treatment has improved steadily. The treatment strategies currently used to treat the disease provide excellent long-term survival (30-year survival rates range from 68.5% to 90.5%).