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Seattle Veterinary Specialists Clinical Update
WHAT IS A HEART
MURMUR?
Did you know
The two sounds of the heartbeat
are created by heart valves
closing.
A heart murmur can be present at birth due to congenital defects, or may
develop later in life secondary to heart disease.
Heart murmurs are abnormal whooshing or swishing sounds that occur during the heartbeat cycle. The
murmur is created by turbulent blood in or near the heart. These sounds can be heard with a
stethoscope. A normal heartbeat makes two sounds, often described as “lub-dub”, which are the
sounds of the heart valves closing.
Heart murmurs can be present at birth (congenital) or develop later in life. A heart murmur isn't a
disease, but murmurs may indicate an underlying heart problem.
Some heart murmurs are harmless (innocent) and don't need treatment. Some heart murmurs are due
to mild heart disease which may require follow up to determine the progressiveness of the disease.
Treatment, if needed, is directed at the cause of the murmur.
An abnormal heart murmur usually has no obvious other signs, aside from the unusual sound your
veterinarian hears when listening with a stethoscope. But if your pet has any of these signs or
symptoms, they may indicate a heart problem:
• Difficulty breathing
• Coughing
• Exercise intolerance
• Fainting
• Lethargy
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Acquired diseases that cause heart murmurs include
degenerative valve disease and cardiomyopathy.
Murmurs in very young puppies and kittens may be benign, or
innocent if they are very soft. These soft murmurs should go away by
the age of 4 months. If they haven’t gone away or if the murmur is
quite loud, then the murmur may be due to a congenital heart disease
which is a structural heart defect. Common congenital defects that
cause heart murmurs include:
•
•
Holes in the heart or cardiac shunts. Many heart murmurs in
puppies and kittens are the result of holes in the walls between
heart chambers, known as septal defects. These may or may
not be serious, depending on the size of the hole and its
location. Shunts occur when there's an abnormal blood flow
between the heart chambers or blood vessels, leading to a
heart murmur. One of the most common types of shunts seen
in puppies is a patent ductus arteriosis (PDA).
Heart valve abnormalities. Examples include valves that don't
allow enough blood through them (stenosis), such as pulmonic
stenosis (PS) or subaortic stenosis (SAS), or those that don't
close properly and leak (regurgitation).
Diagnostics
Auscultation involves listening to
the heart with a stethoscope
Common acquired diseases in older animals that cause heart
murmurs include:
•
•
Degenerative valve disease. This is thickening and irregularity
of the valve that make it so that the valve doesn’t close
properly. These changes occur with age. This type of disease
is common in smaller breed dogs. The most commonly
affected valve is the mitral valve which is the valve between the
left atrium and ventricle (the heart’s left upper and lower
chambers), but the tricuspid valve (the valve between the right
atrium and ventricle) is also often affected.
Cardiomyopathy. Both cats and dogs can have primary
disease of the heart muscle that results in a murmur. The most
common heart disease in cats is hypertrophic cardiomyopathy
(HCM) in which the heart muscle is abnormally thickened; while
dogs can get dilated cardiomyopathy (DCM) in which the heart
muscle is weak and does not contract normally.
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An ECG is an electronic recording
of the heart
Echocardiography is an ultrasound
of the heart
There aren’t any risk factors for abnormal heart murmurs, however, there are risk factors that increase the
chance of having a particular underlying condition that can
cause a heart murmur including age, breed, previous medical
history, other underlying medical conditions, and family history
of your pet.
To determine whether the murmur requires further testing, your
veterinarian will consider:
• What breed and age is your pet? Is your pet showing
any symptoms? What is the previous family history (if it is
available)?
• How loud is it? This is rated on a scale from 1 to 6, with 6
being the loudest.
• Where in the heart is it?
• When does it occur, and for how long? If the murmur happens throughout the heartbeat (continuous
murmur), this most likely indicates a heart problem.
• Species. It is difficult to know if a murmur in a cat is innocent or due to heart disease. There is a
30-40% chance a murmur in a cat is due disease. The only way to know is to perform an
echocardiogram. Therefore, if your cat has a murmur, an echocardiogram will likely be
recommended.
If your veterinarian thinks the heart murmur is significant, they may suggest the following non-invasive
tests:
• Chest X-ray. A chest X-ray shows an image of the heart, lungs and blood vessels. It can reveal if
the heart is enlarged which will let your vet know if the murmur is due to significant heart disease. If
the images from the chest x-ray are unclear or if the heart appears significantly enlarged, they may
recommend an echocardiogram and consultation with a cardiologist.
• Electrocardiogram (ECG). In this test, probes are placed on the limbs to record the electrical
impulses that make the heart beat. An ECG records these electrical signals and can help your vet
look for heart rhythm problems.
• Echocardiogram. This noninvasive exam performed by a cardiology specialist is an ultrasound that
shows detailed images of the heart's structure and function. Ultrasound waves are transmitted, and
their echoes are recorded with a device called a transducer that's held outside of the body. A
computer uses the information from the transducer to create moving images on a video monitor.
This test identifies abnormal heart valves and most heart defects; and allows for more specific and
accurate quantification of heart enlargement (vs. x-rays).
If your pet has an abnormal heart murmur, treatment may not be necessary. Your veterinarian may want to
monitor the condition over time. If treatment is necessary, it depends on what heart problem is causing the
murmur and may include medications or surgery (for congenital heart defects such as PDA or PS).
Adonia Hsu, VMD, DACVIM (Cardiology)
Hours of Operation
For after hours emergencies contact
Seattle Veterinary Specialists
425.823.9111
11814 115th Avenue Northeast
Kirkland, WA 98034-6946
www.svsvet.com
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