Overview
of Congenital Heart Disease
Nine out
of every 1,000 babies born in the United States
have a congenital (present at birth) heart defect
- a problem that occurred as the baby's heart
was developing during pregnancy, before the baby
is born. Congenital heart defects are the most
common birth defects.
A baby's
heart begins to develop at conception, but is
completely formed by eight weeks into the pregnancy.
Congenital heart defects happen during this crucial
first eight weeks of the baby's development. Specific
steps must take place in order for the heart to
form correctly. Often, congenital heart defects
are a result of one of these crucial steps not
happening at the right time, leaving a hole where
a dividing wall should have formed, or a single
blood vessel where two ought to be, for example.
The
vast majority of congenital heart defects have
no known cause. Mothers will often wonder if something
they did during the pregnancy caused the heart
problem. In most cases, nothing can be attributed
to the heart defect. Some heart problems do occur
more often in families, so there may be a genetic
link to some heart defects. Some heart problems
are likely to occur if the mother had a disease
while pregnant and was taking medications, such
as anti-seizure medicines. However, most of the
time, there is no identifiable reason as to why
the heart defect occurred.
Congenital
heart problems range from simple to complex. Some
heart problems can be watched by the baby's physician
and managed with medicines, while others will
require surgery, sometimes as soon as in the first
few hours after birth. A baby may even "grow out"
of some of the simpler heart problems, such as
patent ductus arteriosus (PDA) or atrial septal
defect (ASD), since these defects may simply close
up on their own with growth. Other babies will
have a combination of defects and require several
operations throughout their lives.
We can
classify congenital heart defects into several
categories in order to better understand the problems
the baby will experience. They include:
- problems that cause
too much blood to pass through the lungs
These defects allow oxygen-rich blood that should
be traveling to the body to re-circulate through
the lungs, causing increased pressure and stress
in the lungs.
- problems that cause
too little blood to pass through the lungs
These defects allow blood that has not been
to the lungs to pick up oxygen (and, therefore,
is oxygen-poor) to travel to the body. The body
does not receive enough oxygen with these heart
problems, and the baby will be cyanotic, or
have a blue coloring.
- problems that cause
too little blood to travel to the body
These defects are a result of underdeveloped
chambers of the heart or blockages in blood
vessels that prevent the proper amount of blood
from traveling to the body to meet its needs.
Again,
in some cases there will be a combination of several
heart defects, making for a more complex problem
that can fall into several of these categories.
Some
of the problems that cause too much blood to pass
through the lungs include the following:
- patent ductus arteriosus
(PDA) - this defect, which normally
occurs during fetal life, short circuits the
normal pulmonary vascular system and allows
blood to mix between the pulmonary artery and
the aorta. Prior to birth, there is an open
passageway between the two blood vessels, which
closes soon after birth. When it does not close,
some blood returns to the lungs. Patent ductus
arteriosus is often seen in premature infants.
- atrial septal defect
(ASD) - in this condition, there
is an abnormal opening between the two upper
chambers of the heart - the right and left atria
- causing an abnormal blood flow through the
heart. Some children may have no symptoms and
appear healthy. However, if the ASD is large,
permitting a large amount of blood to pass through
the right side, symptoms will be noted.
- ventricular septal
defect (VSD) - in this condition,
a hole in the ventricular septum (a dividing
wall between the two lower chambers of the heart
- the right and left ventricles) occurs. Because
of this opening, blood from the left ventricle
flows back into the right ventricle, due to
higher pressure in the left ventricle. This
causes an extra volume of blood to be pumped
into the lungs by the right ventricle, which
can create congestion in the lungs.
- atrioventricular canal
(AVC or AV canal) - atrioventricular
canal is a complex heart problem that involves
several abnormalities of structures inside the
heart, including atrial septal defect, ventricular
septal defect, and improperly formed mitral
and/or tricuspid valves.
Some
of the problems that cause too little blood to
pass through the lungs include the following:
- pulmonary atresia
(PA) - a complicated congenital
defect in which there is abnormal development
of the pulmonary valve. Normally, the pulmonary
valve is found between the right ventricle and
the pulmonary artery. It has three leaflets
that function like a one-way door, allowing
blood to flow forward into the pulmonary artery,
but not backward into the right ventricle.
With pulmonary atresia, problems with valve
development prevent the leaflets from opening,
therefore, blood cannot flow forward from the
right ventricle to the lungs.
- transposition of the
great arteries (TGA) - with this
congenital heart defect, the positions of the
pulmonary artery and the aorta are reversed,
thus:
- the aorta originates
from the right ventricle, so most of the
blood returning to the heart from the body
is pumped back out without first going to
the lungs.
- the pulmonary artery
originates from the left ventricle, so that
most of the blood returning from the lungs
goes back to the lungs again
- double outlet right
ventricle (DORV) - a congenital
heart defect (one that occurs as the heart is
forming during pregnancy) in which both the
aorta and the pulmonary artery are connected
to the right ventricle.
- truncus arteriosus
- the aorta and pulmonary artery
start as a single blood vessel, which eventually
divides and becomes two separate arteries. Truncus
arteriosus occurs when the single great vessel
fails to separate completely, leaving a connection
between the aorta and pulmonary artery.
Some
of the problems that cause too little blood to
travel to the body include the following:
- coarctation of the
aorta (CoA) - in this condition,
the aorta is narrowed or constricted, obstructing
blood flow to the lower part of the body and
increasing blood pressure above the constriction.
Usually there are no symptoms at birth, but
they can develop as early as the first week
after birth. If severe symptoms of high blood
pressure and congestive heart failure develop,
surgery may be considered.
- aortic stenosis (AS)
- in this condition, the aortic
valve between the left ventricle and the aorta
did not form properly and is narrowed, making
it difficult for the heart to pump blood to
the body. A normal valve has three leaflets
or cusps, but a stenotic valve may have only
one cusp (unicuspid) or two cusps (bicuspid).
Although aortic stenosis may not cause symptoms,
it may worsen over time, and surgery may be
needed to correct the blockage - or the valve
may need to be replaced with an artificial one.
A complex
combination of heart defects known as hypoplastic
left heart syndrome can also occur.
- hypoplastic left heart
syndrome (HLHS) - a combination
of several abnormalities of the heart and the
great blood vessels. In hypoplastic left heart
syndrome, most of the structures on the left
side of the heart (including the left ventricle,
mitral valve, aorta, and aortic valve) are small
and underdeveloped. The degree of underdevelopment
differs from child to child. The functional
ability of the left ventricle can be reduced
to the extent of not being able to pump an adequate
blood volume to the body. Hypoplastic left heart
syndrome can be fatal without treatment.
Babies
with congenital heart problems are followed by
specialists called pediatric cardiologists. These
physicians diagnose heart defects and help manage
the health of children before and after surgical
repair of the heart problem. Specialists who correct
heart problems in the operating room are known
as pediatric cardiovascular or cardiothoracic
surgeons.
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