The ductus arteriosus is a normal connection in utero between the pulmonary artery and the aorta. Since the lungs are still developing, the baby receives oxygenated blood from the mother during pregnancy. The ductus arteriosus allows the greater part of the oxygenated blood to bypass the non-aerated lungs by flowing directly from the pulmonary artery to the aorta. After the baby is born and begins breathing, hormonal changes occur causing the ductus arteriosus to close. A patent ductus arteriosus, or PDA, is when this connection does not close as it normally should. If the ductus remains open, the direction of flow reverses and some of the oxygen-rich blood from the aorta flows to the pulmonary artery and into the lungs. This may cause an excessive amount of blood flow to the lungs.
There are two reasons that necessitate the closure of a PDA. The first is the size of the ductus, which in turn determines the volume of extra blood being directed to the lungs. A large volume overload may result in enlargement of the heart and over time heart failure. The second reason is to avoid the risk of developing an infection in the heart known as endocarditis. Approximately, one-eighth of patients with a PDA will develop endocarditis. This increases mortality by 50% whereas the risk of surgery is almost zero.
Depending on the size of the ductus, a PDA may be treated in one of two ways. If the ductus is large, the child may require surgery that involves closing off the ductus with a clamp or suture. However, in many cases, the PDA can be closed using a spring coil or a synthetic plug. Both devices are introduced through a heart catheter, which is passed through a vein in the leg that leads up to the heart.
How Does Patent Ductus Arteriosus (PDA) Differ From Normal Cardiac Anatomy?
If your child has patent ductus arteriosus (PDA) or another congenital heart defect, there's usually something wrong with the structure of his or her heart.
Heart with Normal Cardiac Anatomy
When your child has a congenital heart defect, there's usually something wrong with the structure of his or her heart's structure.
The heart is composed of four chambers. The two upper chambers, known as atria, collect blood as it flows back to the heart. The two lower chambers, known as ventricles, pump blood with each heartbeat to the two main arteries (the pulmonary artery and the aorta). The septum is the wall that divides the heart into right and left sides. The atrial septum separates the right and left atria; likewise, the ventricular septum separates the two ventricles.
There are four valves that control the flow of blood through the heart. These flap-like structures allow blood to flow in only one direction. The tricuspid and mitral valves, also known as the atrioventricular valves, separate the upper and lower chambers of the heart. The aortic and pulmonary valves, also known as the arterial valves, separate the ventricles from the main arteries. Oxygen-depleted blood returns from the body and drains into the right atrium via the superior and inferior vena cavas. The blood in the right atrium then passes through the tricuspid valve and enters the right ventricle.
Next, the blood passes through the pulmonary valve, enters the pulmonary artery, and travels to the lungs where it is replenished with oxygen. The oxygen-rich blood returns to the heart via the pulmonary veins, draining into the left atrium. The blood in the left atrium passes through the bicuspid, or mitral, valve and enters the left ventricle.
Finally, the oxygen-rich blood flows through the aortic valve into the aorta and out to the rest of the body.
From Nemours' KidsHealth
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Tetralogy of Fallot
Each year, 4 out of every 10,000 babies born in the United States have the condition, which was named after the French doctor who first described it in the late 1800s, Étienne Fallot. About 10% of all babies born with a heart problem have tetralogy of Fallot.
The four defects that together make up tetralogy of Fallot are:
- Ventricular septal defect (VSD), which is a hole in the septum, or wall, separating the two lower chambers, or ventricles, of the heart. The septum acts as a barrier that prevents blood from both sides of the heart from mixing together. But when there is a VSD, blood high in oxygen from the left ventricle can mix with blood low in oxygen from the right ventricle.
- Pulmonary stenosis, a narrowing or thickening of the valve that connects the right ventricle to the pulmonary artery, a blood vessel that carries low-oxygen blood from the heart to the lungs, where the blood receives more oxygen and then returns to the heart. With pulmonary stenosis, the heart has to work harder than normal to pump blood to the lungs. Often, the amount of blood reaching the lungs is below normal.
- Right ventricular hypertrophy (say hi-PER-truh-fee), which is a thickening of the muscular wall of the right ventricle.
- An "overriding aorta," which means the artery that carries high-oxygen blood to the body is out of place and arises above both ventricles, instead of just the left ventricle, as in a healthy heart. This allows some blood that is low in oxygen to flow into the aorta and out to the body, instead of to the pulmonary artery, which would normally take it to the lungs to pick up oxygen.
The combined effect of these defects is an inadequate supply of blood to the lungs, which causes blood low in oxygen to circulate to the rest of the body. This lower oxygen level causes cyanosis, which is a blue or purple tint to the skin, lips, and fingernails.
Children with tetralogy of Fallot:
- might experience dizziness, fainting, or seizures
- are at a higher risk of developing an infection of the inner layer of the heart called endocarditis
- can have an irregular heartbeat, called an arrhythmia, which with TOF is caused by elevated pressure in the right side of the heart
A child whose TOF is not repaired might need to limit his or her participation in competitive sports and other physical activities. Many infants who have surgery to correct the defect do very well, participate in normal kid activities, and live to adulthood.
Science has not yet identified a specific cause for tetralogy of Fallot in all cases, but genetics is believed to play a role. Someone born with TOF seems more likely to have a child with it.
Mothers who contract rubella or other viral illnesses during their pregnancies are at a higher risk of giving birth to babies with TOF. Other risk factors and conditions include poor nutrition, alcohol abuse, diabetes, and mother's age (over 40).
According to the Centers for Disease Control and Prevention (CDC), the presence of certain environmental factors, such as carbon monoxide, might increase a mother's chances of delivering a baby with TOF. In addition, children who have certain genetic disorders, such as Down syndrome and DiGeorge syndrome, often have congenital heart defects, including tetralogy of Fallot.
One of the most common signs of tetralogy of Fallot is cyanosis (a blue or purple tint to the baby's skin, lips, and fingernails). A child with TOF might experience sudden episodes of cyanosis, called "Tet spells," during crying or feeding.
Other signs include:
- heart murmur
- easy tiring with exertion
- difficulty breathing
- rapid heartbeat (palpitations)
- "clubbing," where the skin or bones around the tips of fingers are widened or rounded
Your doctor may use several diagnostic tests to determine if your child has tetralogy of Fallot, including:
- pulse oximeter: a small sensor that clips onto the fingertip, toe, or ear and measures how much oxygen is in the blood
- electrocardiogram (or EKG): a test that records the electrical activity of the heart
- echocardiogram, or "echo": an ultrasound picture of the heart structures (chambers, walls, and valves). It records the motion of the blood through the heart and can measure the direction and speed of blood flow within the heart structures.
- chest X-ray
- cardiac catheterization: a thin, flexible tube called a catheter is inserted into the heart, usually through a vein in the leg or arm, and provides information about the heart structures as well as blood pressure and blood oxygen levels within the heart chambers. Sometimes a device will be inserted into the heart or blood vessels through the heart catheter.
Tetralogy of Fallot is repaired through open-heart surgery soon after birth or later in infancy, depending on the baby's health and weight and severity of defects and symptoms.
The two surgical options are:
- Complete intracardiac repair: the surgeon widens or replaces the pulmonary valve and enlarges the passageway between the right ventricle and the pulmonary artery to improve blood flow to the lungs. Then, the ventricular septal defect is patched to stop the mixing of high-oxygen blood with low-oxygen blood between the ventricles.
These repairs also fix the two remaining defects (overriding aorta and right ventricular hypertrophy). Because the right ventricle doesn't have to work as hard to pump blood into the lungs, the thickness of the ventricle wall will decrease. And the patched VSD prevents blood with low oxygen from flowing into the aorta.
- Temporary or palliative surgery: only minor repairs are made to improve blood flow to the lungs. This usually only occurs when the baby is too weak or small to undergo full surgery. In the temporary surgery, the surgeon creates a secondary route for blood to travel to the lungs for oxygen. This is done by placing a small tube, called a shunt, between a large artery branching off the aorta and the pulmonary artery.
Later when the baby grows stronger, the full repair is performed.
Most babies born with tetralogy of Fallot do very well and survive to adulthood, but require yearly follow-up with a heart specialist.
Reviewed by: Gina Baffa, MD
Date reviewed: February 2012