tetralogy of Fallot

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Tetralogy of Fallot

 

Definition

Tetralogy of Fallot is a common syndrome of congenital heart defects.

Description

The heart is two pumps in one. The ventricle on the left side pumps blood full of oxygen through the body; the ventricle on the right side pumps the same blood through the pulmonary artery to the lungs to take up oxygen. The left ventricle operates at pressures about four times as high as the right ventricle. Blood is supposed to flow through one side, then the other.
Tetralogy of Fallot is a condition that is characterized by several congenital heart defects occurring at once. They include:
  • ventricular septal defect (Abnormal passageway between the right and left ventricles)
  • displaced aorta
  • narrowed pulmonary valve
  • thickened right ventricle wall
Tetralogy of Fallot is a common syndrome of congenital heart defects. This condition, present in utero, is caused by the narrowing of the pulmonary artery and a hole between the ventricles. When the baby is born and begins to breathe on its own, the baby turns cyanotic, or blue, due to the deoxygenated blood that bypasses the lungs because the narrowed pathway and the hole between the ventricles has remained open.
Tetralogy of Fallot is a common syndrome of congenital heart defects. This condition, present in utero, is caused by the narrowing of the pulmonary artery and a hole between the ventricles. When the baby is born and begins to breathe on its own, the baby turns cyanotic, or blue, due to the deoxygenated blood that bypasses the lungs because the narrowed pathway and the hole between the ventricles has remained open.
(Illustration by Electronic Illustrators Group.)
Each defect acts in combination with the others to create a malfunction of the heart. The problem starts very early in the uterus with a narrowed pulmonary valve and a hole between the ventricles. This is not particularly a problem for a fetus because hardly any blood flows through the lungs until birth. It is only after birth that the defects pose a problem. The blood that is supposed to start flowing through the lungs cannot easily get there because of the narrowed valve; however, the hole between the ventricles remains open. Because of the opening between ventricles, much of the blood that comes back to the heart needing oxygen is sent out without being properly oxygenated. In addition, the right heart has to pump at the same pressure as the left side. Several changes follow. First, the baby turns blue (cyanotic) because of the deoxygenated blood that bypasses the lungs. Deoxygenated blood is darker and appears blue through the skin. Second, the right side of the heart (ventricle) hypertrophies (gets more muscular) from the extra exercise demanded of it. Next, the low oxygen causes the blood to get thicker and clot more easily. Clots in the veins can now pass through the hole in the heart and directly enter the aorta, where they can do much more damage than in the lungs—such as causing infarcts in the brain. In addition, these anomalies make the lining of the heart more susceptible to infection—endocarditis—which can damage valves and lead to blood poisoning (septicemia).

Causes and symptoms

Tetralogy of Fallot is a congenital defect with unknown causes.
Babies with tetralogy of Fallot are blue at birth (cyanosis). Sometimes the blue color appears only when they cry. They also have detectable heart murmurs. Infants with mild forms can have surgery postponed until they are older. Infants with more severe symptoms often have attacks of worsened cyanosis. During attacks, they turn very blue, have shortness of breath, and can faint. This usually occurs during heightened activity, such as crying.

Diagnosis

A complete evaluation of the circulation is required, including testing the blood for its oxygen content; ultrasound; and x rays of the heart accompanied by a contrast agent to determine the amount of blood flowing in the wrong direction. A search for other birth defects is also necessary, because they tend to happen together.

Treatment

Correction of the defects are done through surgery. Surgery must be carefully timed with attention to the progression of the disease process, the size of the infant, and the size of the various defects. There are temporary surgical procedures that can prolong the time before corrective surgery while the baby grows larger and stronger.
During surgery, the pulmonary valve is widened, the ventricular septal defect is closed, and any interim corrections removed.

Prognosis

Surgical correction has a high rate of success, returning the child to near—normal health.

Resources

Books

Friedman, William F., and John S. Child. "Congenital Heart Disease in the Adult." In Harrison's Principles of Internal Medicine, edited by Anthony S. Fauci, et al. New York: McGraw-Hill, 1997.

Key terms

Aorta — Main arterial trunk that moves blood from the heart to the arteries, which transport the blood throughout the body.
Cyanosis — Blue-colored skin due to oxygen-deficient blood.
Endocarditis — Inflammation of the lining of the heart.
Infarct — Death of tissue due to shutting off the blood supply.
Septicemia — Blood poisoning.
Systemic circulation — Through the body, as opposed to "pulmonary"—through the lungs.
Ventricles — The muscular chambers of the heart that do the pumping.

tetralogy

 [tet-ral´ah-je]
a group or series of four.
tetralogy of Fallot a congenital heart defect that combines four structural anomalies: obstruction to pulmonary flow; ventricular septal defect (abnormal opening between the right and left ventricles); dextroposition of the aorta (aortic opening overriding the septum and receiving blood from both ventricles); and right ventricular hypertrophy (increase of volume of the myocardium of the right ventricle).



Infants with this condition are sometimes referred to as blue babies because of the presence of cyanosis, an outstanding symptom. This is due to mixing of poorly oxygenated blood from the systemic circulation with oxygenated blood from the lungs, because of the position of the aorta. Other symptoms include clubbing of the ends of the fingers, hemoptysis, dyspnea on exertion, and a slight delay in growth and development.

Diagnosis is confirmed by electrocardiography, angiocardiography, and cardiac catheterization. These procedures demonstrate changes in the heart's electric impulses; defects in the ventricles, aorta, and pulmonary artery; and, from samplings of blood taken from the various chambers of the heart and great vessels, the oxygen content and pressure of the blood in these various areas.

Treatment involves surgical correction whenever possible. Without corrective surgery the prognosis is extremely poor for children who are deeply cyanotic and have dyspnea on slight exertion.

Before surgery, medical treatment is necessary to avoid complications and control dyspneic attacks. Since the hematocrit is high and polycythemia is common, efforts must be made to prevent dehydration and avoid the development of thrombi. Paroxysmal dyspnea, which often follows feeding or a spell of crying, usually can be relieved by placing the infant in knee-chest position, administering oxygen, or administering a mild sedative or morphine.

Surgical procedures for correction of the defects in the heart and great vessels vary according to the severity of symptoms and the age of the patient. In some cases an anastomosis of the arteries may be done as a temporary measure until more extensive surgery is feasible. In most cases open heart surgery is most successful in relieving symptoms and produces the most lasting benefits.
Tetralogy of Fallot. The right ventricular outflow tract obstruction results in blood flowing from right to left across the ventricular septal defect. From Lissauer and Graham, 2002.

te·tral·o·gy of Fal·lot

(fah-lō), [MIM*187500]
a set of congenital cardiac defects including ventricular septal defect, pulmonic valve stenosis or infundibular stenosis, and dextroposition of the aorta so that it overrides the ventricular septum and receives venous as well as arterial blood. Right ventricular hypertrophy is considered part of the tetralogy although it is reactive to the other defects.
Synonym(s): Fallot tetrad

tetralogy of Fallot

(fă-lō′)
n.
A congenital malformation of the heart characterized by a defect in the ventricular septum, misplacement of the origin of the aorta, narrowing of the pulmonary artery, and enlargement of the right ventricle.

tetralogy of Fallot

[falō′]
Etymology: Gk, tetra, four, logos, word; Etienne-Louis A. Fallot, French physician, 1850-1911
a congenital cardiac anomaly that consists of four defects: pulmonary stenosis, ventricular septal defect, malposition of the aorta so that it arises from the septal defect or the right ventricle, and right ventricular hypertrophy. The primary symptoms in the infant are cyanosis, hypoxia, difficulty in feeding, failure to gain weight, and poor development. In older children a squatting position and clubbing of the fingers and toes are evident. A pansystolic murmur is usually heard, and the second heart sound is faint or absent. Diagnosis of the condition is primarily based on the patient's history and physical symptoms, although cardiac catheterization is performed to evaluate the severity of the defects. Initial treatment consists mainly of supportive measures and palliative surgical procedures, primarily systemic to pulmonary anastomoses to decrease tissue hypoxia and prevent complications until the child is old enough to tolerate total corrective surgery. The optimal age for surgical repair is approximately 1 year. Also called Fallot's syndrome. See also blue baby, trilogy of Fallot.
enlarge picture
Tetralogy of Fallot

tetralogy of Fallot

Pediatric cardiology A cyanotic congenital heart disease, defined by obstruction of the right ventricular outflow, VSD, right ventricular hypertrophy, and an overriding aorta Risk factors Maternal rubella, viral illness during pregnancy, poor prenatal nutrition, maternal alcoholism, mother > age 40, gestational DM, trisomy 21 Clinical At birth, infants are not cyanotic, but later may develop episodic cyanosis from crying or feeding–called "Tet spells"

te·tral·o·gy of Fal·lot

(te-tral'ŏ-jē fahl-ō')
A set of congenital cardiac defects including ventricular septal defect, pulmonic valve stenosis or infundibular stenosis, and dextroposition of the aorta so that it overrides the ventricular septum and receives venous as well as arterial blood. Right ventricular hypertrophy is considered part of the tetralogy, although it is reactive to the other defects.
Synonym(s): Fallot tetrad.

tetralogy of Fallot

See FALLOT'S TETRALOGY.

Fallot,

Étienne-Louis A., French physician, 1850-1911.
Fallot tetrad - Synonym(s): tetralogy of Fallot
Fallot tetralogy - Synonym(s): tetralogy of Fallot
Fallot triad - Synonym(s): trilogy of Fallot
pentalogy of Fallot - Fallot tetralogy with, in addition, a patent foramen ovale or atrial septal defect.
tetralogy of Fallot - a set of congenital cardiac defects. Synonym(s): Fallot tetrad; Fallot tetralogy
trilogy of Fallot - atrial septal defect associated with pulmonic stenosis and right ventricular hypertrophy. Synonym(s): Fallot triad

tetralogy of Fallot,

n.pr a congenital heart defect that comprises the following four characteristics: ventricular septic defect, pulmonary stenosis, right ventricular hypertrophy, and aortic malposition; originates from the right ventricle or septal defect. In newborns and infants, the condition manifests in hypoxia, cyanosis, inability to gain weight, marked difficulty to feed, and poor development. In older children, the condition is distinguished by clubbing of the toes and fingers and squatting. Treatment involves implementing supportive measures and surgery. Also called
Fallot's syndrome.

te·tral·o·gy of Fal·lot

(te-tral'ŏ-jē fahl-ō') [MIM*187500]
A set of congenital cardiac defects including ventricular septal defect, pulmonic valve stenosis or infundibular stenosis, and dextroposition of the aorta such that it overrides the ventricular septum and receives venous as well as arterial blood.

tetralogy

a group or series of four.

tetralogy of Fallot
a congenital defect of the heart that combines four structural anomalies: pulmonary stenosis (narrowing of the pulmonary artery); ventricular septal defect, or abnormal opening between the right and left ventricles; dextroposition of the aorta, in which the aortic opening overrides the septum and receives blood from both the right and left ventricles; and right ventricular hypertrophy, or increase of volume of the myocardium of the right ventricle.
This is almost always a lethal defect. There is poor exercise tolerance, dyspnea, often cyanosis. A loud murmur and a strong thrill are palpable on the left side.