What is hypoplastic left
heart syndrome?
Hypoplastic Left Heart Syndrome (HLHS) is a condition in which the left side
of the heart is underdeveloped. Usually, the left ventricle, the left atrium,
the mitral valve and the aorta are affected. It is called a syndrome because
it can encompass several different variations and varying degrees of
development of these parts of the heart.
To
understand HLHS, it is helpful to understand how a normal baby's heart works.
The heart is comprised of four chambers: the upper chambers are called the
left and right atria, and the lower chambers are called the left and right
ventricles.
Very
simply, in a healthy heart blood flows from the right atrium to the right
ventricle where it is then pumped through the pulmonary artery to the lungs to
be oxygenated. Blood then flows back to the heart via the left atrium to the
left ventricle, which pumps this oxygenated blood through the aorta out to the
body. This is how the body's organs and tissue receive oxygen, which is
vital. When a baby has HLHS, the left side of the heart is underdeveloped so
it cannot sufficiently pump the oxygenated blood out to the body.
Babies
with HLHS do not have problems while in the womb - it is only after birth that
the heart fails to work properly. This is because all babies receive oxygen
from the placenta while in the womb, so blood does not need to go to the
lungs. However,
babies can suffer in-utero demise due to extraneous pressure placed on the
grossly underdeveloped heart from the growing fetus.
In addition, there is an opening between the pulmonary artery and the
aorta, called the patent ductus arteriosus (PDA) that is present in all
babies. It allows the blood to go from the right ventricle out to the body,
bypassing the left side of the heart.
The
PDA usually closes a few days after birth, separating the left and right sides
of the heart. It is at this time that babies with undetected HLHS will
exhibit problems as they experience a lack of blood flow to the body. They
may look blue, have trouble eating, and breathe rapidly. If left untreated,
this heart defect is fatal - usually within the first few days or weeks of
life.
Once
HLHS has been diagnosed, a drug called prostaglandin is given to keep the PDA
open until surgery is performed. There are
two
surgical options
for treating HLHS: a Heart Transplant or the 3-Stage Surgical Procedure, the
first stage of which is called the Norwood procedure.
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