Tetralogy of Fallot is the most common heart defect in children. The condition causes mixing of oxygen-poor blood with the oxygen-rich blood being pumped out of the heart and into the circulatory system of blood vessels.
· The blood leaving the heart has less oxygen than is needed by the organs and tissues of the body, a condition called hypoxemia.
· Chronic (ongoing, long-term) lack of oxygen causes cyanosis, a bluish color of the skin, lips, and membranes inside the mouth and nose.
The normal heart works as follows:
· The heart is made up of 4 chambers: 2 upper chambers called atria and 2 lower, larger chambers called ventricles. Each atrium is separated from its paired ventricle by a valve.
· The heart has a left and a right side. The left and right sides of the heart are separated by a septum (wall). The right side of the heart receives oxygen-depleted or blue blood returning by veins (superior vena cava and inferior vena cava) from the body.
· The blood flows from the right atrium through the tricuspid valve into the right ventricle, which pumps it through the pulmonic valve into the pulmonary artery, the main artery to the lungs.
· In the lungs, the blood absorbs oxygen and then returns to the left atrium through the pulmonary veins.
· From the left atrium, the blood is pumped through the mitral valve to the left ventricle. The left ventricle pumps the blood out of the heart into the circulatory system via a large artery known as the aorta.
· The blood moves throughout the body, supplying oxygen and nutrients to organs and cells.
· Organs cannot work properly if they do not receive enough oxygen-rich blood.
The 4 abnormalities (tetralogy) of the heart described by Fallot include the following:
· Right ventricular hypertrophy: Narrowing or blockage of the pulmonary valve and/or muscle under the pulmonary valve coming out of the right ventricle. This restriction to blood outflow causes an increase in right ventricular work and pressure, leading to right ventricular thickening or hypertrophy.
· Ventricular septal defect (VSD): This is a hole in the heart wall (septum) that separates the 2 ventricles. The hole is usually large and allows oxygen-poor blood in the right ventricle to pass through, mixing with oxygen-rich blood in the left ventricle. This poorly oxygenated blood is then pumped out of the left ventricle to the rest of the body. The body gets some oxygen, but not all that it needs. This lack of oxygen in the blood causes cyanosis.
· Abnormal position of the aorta: The aorta, the main artery carrying blood out of the heart and into the circulatory system, exits the heart from a position overriding the right and left ventricles. (In the normal heart, the aorta exits from the left ventricle.) This is not of major importance in infants.
· Pulmonary valve stenosis (PS): The major issue with tetralogy of Fallot is the degree of pulmonary valve stenosis, since VSD is always present. If the stenosis is mild, minimal cyanosis occurs, since blood still mostly travels to the lungs. However, if the PS is moderate to severe, a smaller amount of blood reaches the lungs, since most is shunted right-to-left through the VSD.
Tetralogy of Fallot Symptoms
Most infants with tetralogy of Fallot develop cyanosis in the first year of life.
· The skin, lips, and mucous membranes inside the mouth and nose take on a noticeably dusky blue color.
· Only some infants with very severe obstruction of the right ventricle outflow turn blue at birth.
· A small number of children with tetralogy of Fallot never turn blue at all, especially if the pulmonary stenosis is mild, the ventricular septal defect is small, or both.
· In some children, the cyanosis is quite subtle and may go undetected for some time.
The following symptoms suggest tetralogy of Fallot:
· Growth and development are slower, especially if the pulmonary stenosis is severe. Puberty may be delayed if the tetralogy is untreated.
· The child usually tires easily and begins panting with any form of exertion. He or she may play for only a short time before sitting or lying down.
· Once able to walk, the child often assumes a squatting position to catch his or her breath and then resumes physical activity. Squatting increases the pressure transiently in the aorta and left ventricle, causing less blood to move into the left ventricle, more out the pulmonary artery to the lungs.
Surgery is the primary way to correct the heart problem. Your child may be prescribed medication for tet spells. You will also be given information for dealing with future tet spells.
· The child will be placed on his or her back in the knee-to-chest position to increase aortic resistance. The increased aortic and left ventricular pressure reduces the rush of blood through the septal hole from the right ventricle and improves blood circulation to the lungs, so more red blood reaches the tissues.
· The child may be given oxygen through a face mask to increase the amount of oxygen in the blood.
