What is a heart murmur?
Heart murmur is the noise made by blood as it travels through the heart, similar to the
noise made by water as it run from a faucet. Blood flow in normal circumstances flow
silently. It is when blood starts to flow turbulently that noise is produced, which
could be hear by auscultation and is termed "heart murmur".
Is there more than one kind of heart
Heart murmur could be normal or abnormal.
Normal (innocent) heart murmurs: This is heard in about 50% of all normal
infants. It does not reflect abnormalities of the heart.
Abnormal (pathologic) heart murmurs: This is heard in
patients with heart disease in which there is an abnormal structure of the heart, making
blood travel in an abnormal fashion resulting in a noise also known as heart murmur.
Heart diseases causing murmur include abnormal heart valves which are too tight (stenosis)
or leaky (regurgitation). Other heart diseases which produce heart murmurs include
abnormal communications within the heart (holes in the heart such as atrial septal defect
ASD, ventricular septal defect (VSD), or abnormal communication between blood vessels such
as patent ductus arteriosus (PDA).
Normal Heart Cycle
The ventricles contract to propel blood out through the aorta and pulmonary arteries to
the body and lungs.
What causes a normal (innocent) heart
Many conditions, all within normal limits, may cause the blood to flow with turbulence
leading to a heart murmur on auscultation. All these conditions do not indicate any
abnormality and cause no ill effect on ones health. Some of the conditions causing
an innocent heart murmur are:
Small blood vessels to the lungs (pulmonary arteries) in newborn
children (Peripheral Pulmonary Stenosis or PPS): Newborn babies have small
blood vessels to the lungs, this is because while they were in their mothers' uterus,
there was very little blood flow to the lungs since babies do not breath prior to birth.
This will cause the blood vessels to the lungs to be small (since blood flow causes
blood vessels to grow). Once the child is born, blood flow increases tremendously to
the lungs, this will cause blood to be turbulent as it crosses these relatively small
blood vessels, this turbulence will produce a heart murmur. This disappears at about
2 months of age.
Normal Blood Flow
Normally the blood flows smoothly and silently .
Blood flow through the aortic valve
(Still's murmur) and pulmonary valve (Physiologic pulmonary flow murmur):
Blood flow across these two valves is audible in some children. This is not because
there is anything wrong with these valves, but it may be due to the fact that children
have a faster heart rate, which means that blood normally travels with a higher speed
causing noise, resulting in the heart murmur. Also, children have thinner chest walls,
which allows sounds to be more readily audible.
Venous hum: Sometimes, blood flow through large veins close
to the skin surface in the neck and upper chest could be audible.
Mammary soufflé: Developing breasts in normal
teenage girls may cause the blood flow in the arteries providing blood to the developing
breast tissue to be audible.
How can a doctor tell the difference
between normal (innocent) or abnormal (pathologic) heart murmurs?
Innocent heart murmurs have certain features which are easy to detect by the examining
the doctor would ask questions to see if there are any suggestions of heart disease such
as problems soon after birth, does the child feed well, any fatigue or shortness of breath
from exercise typically tolerated of other children of the same age, and finally any
history of bluish discoloration of the child's lips. These are features suggesting
of heart disease, which if present may suggest that the heart murmur is pathologic and not
the doctor would try to illicit any signs of heart disease when examining the child.
Abnormal findings suggesting heart disease such as evidence of congested lungs or
liver, or swelling of extremities, or bluish discoloration of lips or other mucosa may
suggest heart disease.
In this example there is pulmonary valve stenosis. The small pulmonary valve orifice
causes the blood to be turbulent and noisy which is heard as a heart murmur on
murmur is then assessed. Soft murmurs are normal, harsher ones tend to be
abnormal. Also innocent murmurs tend to soften further or completely disappear when
auscultation is performed while the child is sitting or standing versus when auscultation
is done with child laying down.
tests may be done to confirm the fact that there is no heart disease such as an
electrocardiogram (ECG), chest x-ray or an echocardiogram.
Will my child outgrow an
innocent heart murmur?
If a child has an innocent heart murmur, then the heart is normal and there is nothing to
outgrow. However, the murmur may after few years be no longer audible as the chest
wall gets thicker and the heart rate slows down.