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What is hypoplastic left heart syndrome?
Hypoplastic left heart syndrome is a medical condition that involves the
underdevelopment of the structures of the left side of the heart. The degree of
underdevelopment can vary from baby to baby but the structures involved usually
include the following:
- The left ventricle—is the large lower left-hand chamber
of the heart that pumps oxygen-rich blood out to the body. In this syndrome,
this chamber is very small, poorly developed and therefore is unable to
provide enough blood flow to meet the body’s needs.
- The mitral and aortic valves—the mitral valve is the
valve that controls the amount of blood that flows from the left atrium (the
upper left-hand chamber of the heart) into the left ventricle. The aortic
valve is the valve between the left ventricle and the aorta. In this syndrome,
the valves can be narrowed or closed, hindering the flow of oxygenated blood
out to the body.
- The aorta—is the largest artery in the body; receives
the oxygenated blood from the left ventricle and distributes it to the body.
In this syndrome, the aorta is small and very narrowed, which can block the
flow of oxygenated blood out of the heart and to the body.
This illustration shows the normal heart structures.
This illustration shows some of the malformations seen in
hypoplastic left heart syndrome, which includes a narrowing (in diameter)
of the aorta; a pinching of the aorta; a narrowing or closure of the
mitral and/or aortic valves; and underdevelopment of the left ventricle.
What causes hypoplastic left heart syndrome?
Hypoplastic left heart syndrome occurs in 4 to 16 out of every 10,000 live
births and accounts for about 8% of congenital heart disease in babies.
Underdevelopment of the heart structures occurs during the first 8 weeks of
pregnancy. There is often no clear reason for the development of congenital
heart defects. In some cases, there may be a genetic link or an environmental
exposure that makes the defects occur more often in some families; in other
cases, there is simply no known cause. Hypoplastic left heart syndrome occurs
more often (55% to 70%) in males than females. Babies with this syndrome tend to
also have other cardiovascular and neurologic organ defects.
What are the symptoms of hypoplastic left heart syndrome?
Hypoplastic left heart syndrome can be detected while the baby is still in
the uterus (see next question); however, once born, symptoms usually appear
within a few days after birth. Symptoms, which may vary from baby to baby,
include:
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Pale skin color
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Blue hue to skin, lips, and nailbeds (called cyanosis)
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Difficulty breathing
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Difficulty feeding
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Rapid heart beat
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Sweaty, clammy or cool skin
How is hypoplastic left heart syndrome diagnosed?
Diagnosis of this condition is made based on findings from a physical
examination (listening to the heart and lungs), observation of symptoms (listed
above), and the findings of other diagnostic tests listed below. Hypoplastic
left heart syndrome can be diagnosed while the baby is still in the womb with
the aid of an echocardiogram. This and other diagnostic tests are described
below:
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echocardiogram - a test that uses sound waves to create
a moving picture of the heart’s internal structures.
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doppler ultrasound
is a test that uses sound waves to measure blood flow; often combined with
echocardiogram to evaluate both the internal structure of the heart and blood
flow across the heart’s valves.
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chest X-ray - a test to show the size and shape of the
heart and lungs.
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electrocardiogram (ECG or EKG) - a test that records
the electrical changes that occur during a heartbeat; reveals abnormal heart
rhythms (arrhythmias) and detects heart muscle stress.
How is hypoplastic left heart syndrome treated?
Babies with this condition will die within days to weeks of life if not
treated. Today, babies can be treated in a series of operations that rerout the
function of the left side of the heart. Heart transplantation in another option
though it is limited by the number of infant hearts available and the lifelong
need to take drugs to prevent organ rejection.
After birth
Once the baby is born, three surgical procedures timed to coincide with
the development of the lungs, are performed and are described as follows:
The Norwood Procedure-- This surgery, which rerouts the
blood flow to avoid the left side heart problems, is performed shortly after
birth. The surgery turns the right ventricle—the nondefective ventricle—into
the main "workhorse" ventricle, able to pump blood to both the lungs
and the body. The main pulmonary artery and the aorta are surgically
connected, with a shunt (tube) connecting a branch of the aorta to the
pulmonary artery to supply blood to the lungs. Oxygenated blood is supplied to
the body through other branches of the aorta.
Bi-directional Glenn
Operation -- This second operation usually is performed about 3 to 8
months after the Norwood procedure when the lungs are more mature and don’t
require ventricular force to send blood to the lungs. In this operation, the
shunt to the pulmonary arteries is disconnected and a new shunt connects the
superior vena cava to the pulmonary artery. This new shunt diverts half of the
deoxygenated blood directly to the lungs without the need to go through the
ventricle.
Fontan Operation-- This third
operation usually is performed about 18 to 36 months after the Glenn
operation, a time when the lungs have further matured and the vessels of the
lungs can accommodate all the deoxygenated blood from the lower part of the
body. This operation connects the inferior vena cava—the major blood vessel
that carries deoxygenated blood from the lower part of the
body back to the heart—with the pulmonary artery. This is done by
creating a channel through or just outside the heart to direct blood to the
pulmonary artery. After this operation, blood flows passively through the
lungs, and the single ventricle pumps exclusively oxygenated blood to the
body.
The decision regarding which surgical approach to take will depend on
the baby’s overall health, extent of disease, surgeon’s expertise,
expectations about how the baby’s disease might progress, and parental
opinion. Because these surgeries are complex and need to be individualized for
each baby, your cardiologist will help you decide which medical and surgical
approach will be best for your baby.
Prior to birth
Treatment of hypoplastic left heart syndrome in utero (in the developing
fetus) is a new approach being explored. The following are two emerging
treatment strategies: In a small subset of fetuses in which the hole between the
atria is closed, a new procedure that opens the hole before the baby is born has
been developed. This new procedure is known as fetal balloon atrial
septostomy.
There is another subset of children who develop a problem with the aortic
valve that then leads to enlargement of the left ventricle. The left ventricle
then shrinks causing hypoplastic left heart syndrome. One proposed surgical
strategy is to open the aortic valve before the left ventricle shrinks.
How successful are the various treatment options? Can my child expect to have
a full normal length of life?
Ask your cardiologist about the specific outlook to expect for your baby. The
outlook varies from baby to baby depending on the issues mentioned above. In
addition, each stage of the different surgical repair procedures carries
different risks and complications. Also, the outcomes at each medical facility
itself are different based on the number of cases performed and the surgeon’s
experience. Be sure to ask your cardiologist about these concerns.
Children with hypoplastic left heart syndrome require check-up appointments
throughout their lives to evaluate how well their heart is working. Nearly all
children will require heart medications as well as antibiotics prior to dental
work or other surgeries to reduce the risk of infection to the heart valves (a
condition called endocarditis).
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