Patent ductus arteriosus (PDA) is a heart defect that occurs in infants
when the ductus arteriosus (the temporary fetal blood vessel that connects
the aorta and the pulmonary artery) does not close at birth.
The ductus arteriosus is a temporary fetal blood vessel that connects the
aorta and the pulmonary artery before birth. The ductus arteriosus should
be present and open before birth while the fetus is developing in the
uterus. Since oxygen and nutrients are received from the placenta and the
umbilical cord instead of the lungs, the ductus arteriosus acts as a
"short cut" that allows blood to bypass the deflated lungs
and go straight out to the body. After birth, when the lungs are needed to
add oxygen to the blood, the ductus arteriosus normally closes. The
closure of the ductus arteriosus ensures that blood goes to the lungs to
pick up oxygen before going out to the body. Closure of the ductus
arteriosus usually occurs at birth as levels of certain chemicals, called
prostagladins, change, and the lungs fill with air. If the ductus
arteriosus closes correctly, the blood pumped from the heart goes to the
lungs, back into the heart, and then out to the body through the aorta.
The blood returning from the lungs and moving out of the aorta carries
oxygen to the cells of the body. In some infants, the ductus arteriosus
remains open (or patent), and the resulting heart defect is known as
patent ductus arteriosus. In most cases, a small PDA does not result in
physical symptoms. If the PDA is larger, health complications may occur.
In an average individual's body, the power of blood being pumped by
the heart and other forces leads to a certain level of pressure between
the heart and lungs. The pressure between the heart and lungs of an
individual affected by PDA causes some of the oxygenated blood that should
go out to the body (through the aorta) to return back through the PDA into
the pulmonary artery. The pulmonary artery takes the blood immediately
back to the lungs. The recycling of the already oxygenated blood forces
the heart to work harder as it tries to supply enough oxygenated blood to
the body. In this case, usually the left side of the heart grows larger as
it works harder and must contain all of the extra blood moving back into
the heart. This is known as a left-to-right or aortic-pulmonary shunt.
As noted, the size of the PDA determines how much harder the heart has to
work and how much bigger the heart becomes. If the PDA is large, the
bottom left side of the heart is forced to pump twice as much blood
because it must supply enough blood to recycle back to the lungs and move
out to the body. As the heart responds to the increased demands for more
oxygenated blood by pumping harder, the pulmonary artery has to change in
size and shape in order to adapt to the increased amount and force of the
blood. In some cases, the increase in size and shape changes the pressure
in the pulmonary artery and lungs. If the pressure in the lungs is higher
than that of the heart and body, blood returning to the heart will take
the short cut back into the aorta from the pulmonary artery through the
PDA instead of going to the lungs. This backward flowing of blood does not
carry much oxygen. If blood without much oxygen is being delivered to the
body, the legs and toes will turn blue or cyanotic. This condition is
called a shunt reversal.
When a PDA results in a large amount of blood being cycled in the wrong
order, either through a left-to-right shunt or shunt reversal, the
overworked, enlarged heart may stop working (congestive heart failure) and
the lungs can become filled with too much fluid (pulmonary edema). At this
time, there is also an increased risk for bacterial infection that can
inflame the lining of the heart (endocarditis). These three complications
are very serious.
PDA is a very common heart defect, accounting for 5 to 10 percent of all
congenital heart disease
. Though an exact incidence of PDA is difficult to determine, researchers
estimate that eight or nine in every 1,000 children are affected. PDA can
occur in full-term infants, but it is seen most often in preterm infants,
infants born at a high altitude, and babies whose mothers had a
infection during pregnancy. PDA occurs in individuals of every ethnic
origin and does not occur more often in any one country or ethnic
population; however, it is two to three times more common in females than
Causes and symptoms
PDA can be caused by environmental exposure before birth or the
inheritance of a specific changed or mutated gene or genes. It can be a
symptom of a genetic syndrome or may be caused by a combination of genetic
and environmental factors (multifactorial).
Environmental exposures that can increase the chance for a baby to be
affected by PDA include fetal exposure to rubella before birth, preterm
delivery, and birth at a high altitude location.
PDA can be an inherited condition in families with isolated PDA or part of
a genetic syndrome. In either case, there are specific gene changes or
lead to a defect in the elastic tissue forming the walls of the ductus
arteriosus. As of 2004 the genes causing isolated PDA have not been
identified, but it is known that PDA can be inherited through a
in an autosomal dominant pattern or an autosomal recessive pattern. Every
person has approximately 30,000 genes, which tell the body how to grow and
develop correctly. Each gene is present in pairs since one is inherited
from the mother and one is inherited from the father. In an autosomal
dominant condition, only one specific changed or mutated copy of the gene
for PDA is necessary for a person to have PDA. If a parent has an
autosomal dominant form of PDA, there is a 50 percent chance for each
child to have the same or similar condition.
PDA can also be inherited in an autosomal recessive manner. A recessive
condition occurs when a child receives two changed or mutated copies of
the gene for a particular condition, such as PDA (one copy from each
parent). Individuals with a single changed or mutated copy of a gene for a
recessive condition are known as carriers and have no health problems
related to the condition. However, when two people who each carry a
changed or mutated copy of the same gene for a recessive condition have
children, there is a chance with each pregnancy for the child to inherit
the two changed or mutated copies from each parent. In this case, the
child would have PDA. For two known carriers, there is a 25 percent risk
with each child to have a child with PDA, a 50 percent chance to have a
child who is a carrier, and a 25 percent chance to have a child who is
neither affected nor a carrier.
Most cases of PDA occur as the result of multifactorial inheritance which
is caused by the combination of genetic factors and environmental factors.
The combined factors lead to isolated defects in the elastic tissue
forming the walls of the ductus arteriosus.
The main sign of PDA is a constant heart murmur that sounds like the hum
of a refrigerator or other machinery. This murmur is usually heard by the
doctor using a stethoscope.
Other signs and symptoms of PDA include:
Diagnosis is most often made by detecting the characteristic
"machinery" heart murmur heard by a doctor through a
stethoscope. Tests such as a chest x ray, echocardiograph, and ECG are
used to support the initial diagnosis and to determine the severity of the
The treatment and management of PDA depends upon the size of the PDA, the
presence of other heart defects, and the symptoms experienced by the
affected individual. In some cases, the PDA will close spontaneously and
no further treatment will be required. In individuals for whom the PDA
remains open, there are three treatment options: medical management,
device closure, and surgical repair.
Medical management with medications such as indomethocin is often the
first course of treatment in premature infants with PDA. Indomethocin
causes the muscles within the heart to tighten, closing the PDA. In
infants for whom indomethocin does not close the PDA, full-term infants,
and older children, device closure or surgery may be necessary.
Device closure of PDA is a medical procedure in which a device such as a
coil, very small rings of wire, or an occluder, a tiny wire mesh patch, is
placed over the PDA causing the blood to clot and thus closing the open
ductus. The device is inserted into the heart in a process called cardiac
catheterization. A small thin flexible tube is inserted into a blood
vessel, usually in the groin area, and guided into the heart. The device
is then passed through the catheter to the PDA. For most patients, this
procedure is highly effective, and no further treatment is required. In
children for whom this procedure is unsuccessful, children with very large
PDA, or those with multiple heart defects, surgery may be necessary.
In surgical closure of PDA, called a ligation, the chest cavity is opened,
the blood vessels are separated, and the PDA is sewn closed.
Individuals can survive with a small opening remaining in the ductus
arteriosus. Treatment, including surgery, of a larger PDA is usually
successful and frequently occurs without complications. Proper treatment
allows children to lead normal lives.
While there is no known prevention for PDA, appropriate prenatal care for
expectant women is important and may prevent premature delivery, a major
risk factor for PDA.
—The main artery located above the heart that pumps oxygenated
blood out into the body. The aorta is the largest artery in the body.
—A bluish tinge to the skin that can occur when the blood oxygen
level drops too low.
—The temporary channel or blood vessel between the aorta and
pulmonary artery in the fetus.
—A record of the internal structures of the heart obtained from
beams of ultrasonic waves directed through the wall of the chest.
Electrocardiagram (ECG, EKG)
—A record of the electrical activity of the heart, with each wave
being labeled as P, Q, R, S, and T waves. It is often used in the
diagnosis of cases of abnormal cardiac rhythm and myocardial damage.
—Inflammation of the inner membrane lining heart and/or of the
heart valves caused by infection.
—Blood carrying oxygen through the body.
—An artery that carries blood from the heart to the lungs.
—An accumulation of fluid in the tissue of the lungs.
In addition to slow growth, children with PDA may be more susceptible to
infections such as colds,
, and a rare but potentially life threatening infection of the heart
called endocarditis. Children with PDA may need to receive preventative
prior to dental work. Annual flu vaccines are recommended, and parents
should watch for signs of infection such as
, chills, and any difficulty breathing.
Parents of children with PDA should watch for the following symptoms and
contact the doctor if any of these occurs:
Congenital Heart Anomalies Support, Education, and Resources (CHASER).
2112 North Wilkins Rd., Swanton, OH 43558. Web site:
Kids with Heart.
1578 Careful Dr., Green Bay, WI 54304. Web site:
"Patent Ductus Arteriosus: Signs, Symptoms, Diagnosis, Treatment,
Heart Center Encyclopedia, Cincinnati Children's Hospital Medical
Available online at
Pflieger, Kurt. "Patent Ductus Arteriosus."
, October 29, 2002. Available online at