Definition
Hypoplastic left heart describes the underdevelopment
of the left side of the heart (left ventricle, aortic valve, and aorta). The
condition is congenital (present at birth).
Alternative Names
Hypoplastic left heart syndrome; HLHS
Causes, incidence, and risk factors
Hypoplastic left heart is a rare type of congenital
heart disease. The problem develops before birth when there is inadequate growth
of the left ventricle and associated structures (aortic and mitral valves that
guard the exit and entrance of the ventricle and the aorta which is the blood
vessel that carries oxygenated blood from the left ventricle to the entire
body).
In patients with this condition, the left side of the
heart is unable to maintain circulation for the body. As a result, the right
side of the heart must maintain both pulmonary (lung) and systemic (body) circulation.
This extra workload eventually causes the heart to fail.
The only possibility of survival is a connection
between the right and the left side of the heart through which blood may pass.
This is called a shunt. Babies are normally born with two of these connections
(the foramen ovale and the ductus arteriosus), which spontaneously close a few
days after birth.
If these structures are allowed to close in a baby
with hypoplastic left heart syndrome, however, the patient will quickly die
because no blood will be pumped to the body.
There is no known cause of hypoplastic left heart
syndrome. Up to 40% of patients with this condition have other birth
defects.
Prevention
There is no known prevention for hypoplastic left
heart syndrome. As with many congenital diseases, the causes of hypoplastic left
heart syndrome are uncertain and have not been linked to any maternal diseases
or behavior.
Symptoms
Initially, a newborn with hypoplastic left heart may
appear normal. Symptoms usually occur in the first few hours of life, although
it may take up to a few days to develop symptoms. These symptoms may
include:
- Lethargy
- Poor suckling and feeding
- Shortness of breath
- Rapid breathing
- Cold extremities
- Enlarged liver
- Poor pulse
- Pounding heart
- Bluish or poor skin color
- Sudden death
In healthy newborns, bluish color occurs in
hands and feet as a response to cold (this reaction is called peripheral
cyanosis).
However, a bluish color observed in the chest or
abdomen, lips, and tongue is abnormal (called central cyanosis) because it
reflects lack of adequate levels of oxygen in the blood. This is secondary to
the heart malformation and circulatory malfunction. Central cyanosis often
increases with crying.
Signs and tests
Physical examination
usually reveals a blue, critically ill patient who may show signs of
congestive heart failure, including hepatomegaly (liver enlargement), tachypnea (rapid breathing), and lethargy (inactivity with
decreased mental status). Additionally, the pulse at various locations (wrist, groin,
and others) is usually very weak.
Tests:
- An ECG shows right ventricular hypertrophy (enlargement of the
right ventricle of the heart).
- An X-ray of the
chest shows heart enlargement.
- An echocardiogram for the definitive
diagnosis shows the tiny left ventricle
- A cardiac catheterization may be necessary in some
cases to complement the echocardiogram.
Treatment
Once the diagnosis of hypoplastic left heart is made,
a nunber of things are done. First, the patient is put on a ventilator to assist
with breathing if necessary. A medicine called prostaglandin E1 is started to
prevent a shunt called the ductus arteriosus from closing. Intravenous fluids
are started and medicine to help the heart beat stronger is often
begun.
These measures are only supportive; they do not solve
the problem. The next step is surgery.
There are two surgical approaches to hypoplastic left
heart syndrome. One is to do a heart transplant early in life. This means that a
small donor heart, which is very rare, must be available. It also means that the
patient will have to take a number of medicines to prevent rejection of the new
heart.
The other option is a series of operations done over
the first 3 years of life; this option is called the Norwood procedure. Stage I
of the Norwood procedure is done within the first few days of life and consists
of attaching the functioning right ventricle to the aorta (vessel that delivers
blood to the body).
Because the lungs must still receive blood, a
surgically created conduit (tunnel) is created to attach the a large artery in
the chest to the pulmonary arteries (the vessels that lead to the lungs). This
conduit is called a Blalock-Taussig (BT) shunt.
In the stage II operation, called the Glenn or
Hemi-Fontan procedure, the superior vena cava (the vessel that removes
deoxygenated blood from the head and arms) is attached to the pulmonary arteries
and the BT shunt is removed.
During stage III, called the Fontan procedure, the
inferior vena cava (the vessel that returns deoxyganted blood from the lower
half of the body) is also attached to the pulmonary arteries. This is usually
performed between the ages of 2-3 years. After the third stage the patient is no
longer blue (cyanotic).
The Norwood procedure is relatively new, but outcomes
have been good so far. While it is possible that these patients' hearts
eventually will fail and they will need a heart transplant, it is much easier to
transplant an older patient than an infant.
Complications
If untreated, heart
failure continues to worsen and will result in
death.
Calling your health care provider
If your infant
shows any of the symptoms of hypoplastic left heart syndrome, contact your
health care provider immediately.
