|
Client Library Article
Feline Heart Disease
| FELINE HYPERTROPHIC CARDIOMYOPATHY
(HCM) |
| Hypertrophic cardiomyopathy (HCM) is the most common form of heart disease
in cats. HCM develops slowly over years and
most cats go undiagnosed until they go into heart failure or throw a large
blood clot into the aorta which causes acute pain and paralysis in the hind
legs termed a saddle thrombus. (see saddle thrombus section for more
details). HCM occurs when the heart muscle becomes abnormally thick
which in turn decreases
the size of the heart chambers- or the space in the heart where the blood
collects before it is pumped out to the rest of the body. In HCM, the muscle
contracts well, but can not relax normally due to the thickness of the
muscle. Without this relaxation, there is little room for new blood to
enter the chamber. As the hypertrophy or thickening of the wall progresses, the
heart valves become non-aligned and a murmur often develops as blood flows
backwards across the leaky valve with each heart beat. The regurgitation or
backwards blood flow also causes large blood clots to form in the heart in
many cats. These clots are deadly when a piece breaks off and
travels down the aorta eventually causing a plug (see the saddle thrombus
article for more information). Decreased chamber size, a non-compliant wall and blood
regurgitation across the valves all contribute to a decreased volume of
blood being pumped through the heart to the rest of the body.
Initially, the body
compensates for the decreased cardiac output of blood by increasing the
heart rate and retaining sodium to increase blood volume. As the myopathy
(heart muscle disease) progresses, the chamber size and wall compliance
worsens to the point where the cat goes into congestive heart failure. |
| Diagnosis |
- Physical exam- the veterinarian will
carefully listen to the heart with a stethoscope to listen for heart
murmurs, muffled heart sounds, and irregular beats and rhythms.
The pulses are felt at the same time to identify pulse deficits- when a
heart beat is heard but there is no associated pulse. Pulse strength
and quality is assessed as well.
- In congestive heart failure, the cat will have labored
breathing, a high heart rate, and weak pulses. If the cat has left
sided heart failure, fluid crackles can be heard in the lung fields
indicating pulmonary edema. With right sided heart failure, fluid builds
up in the space around the lungs which makes it difficult for the lungs to
expand with each breath. The build up of fluid is termed pleural
effusion. Most cats present in congestive heart failure and
have both pleural effusion and pulmonary edema indicating
biventricular or left and right sided heart failure.
- Radiographs- are used to evaluate the
heart shape and size. In HCM, the heart is usually a normal size except
for an enlarged atria which shows up as a classic valentine shape.
Since most cats present in heart failure, fluid densities can
be seen in and around the lung fields.
- ECG or electrocardiogram traces out the heart’s
electrical activity and is used to assess rate, rhythm, and heart
enlargement based on the shape and size of different parts of the electrical
complex. A flat line ECG (often seen in the movies) indicates no
electrical activity in the heart which equals death.
- Echocardiogram (cardiac
ultrasound) is the most accurate diagnostic tool for evaluating
the heart. Ultrasounds are used to look at the function of the heart and
to measure the size of the heart chambers, thickness of the walls,
valves, and major vessels. Additionally, blood volume and direction of
flow can be evaluated- which allows the cardiologist to measure cardiac
output (blood volume pumped through the heart) and evaluate the severity
of murmurs.
- In HCM, small
chambers and thickened heart walls are seen along with enlarged atria which
sometimes have a large blood clot in it. There is often a murmur across the
valves that can be measured with doppler. With an echocardiogram, the
cardiologist can accurately assess the degree of heart disease, give a more
accurate prognosis, and most importantly choose the appropriate medication
(s) for each animal.
|
| Treatment of
Hypertrophic Cardiomyopathy |
| Cats with HCM are commonly
treated with diltiazem, a drug that blocks calcium channels and improves
relaxation, and Lasix, a diuretic to help decrease the buildup on fluid in
and around the lungs, and eliminate extra sodium in the urine. Low doses of
aspirin are recommended as well to help prevent blood clots from forming in
the heart. Many other drugs can be used, most on a temporary basis, to
improve cardiac function. It is highly recommended to consult a veterinary
cardiologist for long term management. |
| Prognosis |
| Entirely dependent upon each individual but generally
guarded to poor prognosis for long term survival. With proper
therapy, some cats do well for years. Other cats do not respond to
medication and die quickly in heart failure. |
| FELINE DILATED CARDIOMYOPATHY |
| Dilated cardiomyopathy (DCM) was once the most common form of heart disease in
cats due to a dietary deficiency of taurine- an important nutrient required
for normal heart function. Fortunately, DCM is fairly rare today due to well
balanced quality cat foods available that contain daily requirements of
taurine. Without taurine, the heart muscle cells enlarge leading to a
decreased ability to contract normally. This in turn leads to a decreased
volume of blood being pumped through the heart to the rest of the body. The
body compensates for the decreased cardiac output of blood by increasing the
heart rate and retaining sodium to increase blood volume. As the myopathy
(heart muscle disease) progresses, the heart itself enlarges and the heart
valves start to leak. When this occurs, a heart murmur is heard with each
heart contraction. DCM is a progressive disease which worsens over time
eventually throwing the cat into congestive heart failure. If a cat is
suspected of having DCM, it should be put on supplemental taurine. Any cat
on on home made diet should receive a taurine supplement daily. |
| Symptoms |
|
|
|
Diagnosis of Dilated
Cardiomyopathy
|
-
Physical exam- same parameters as with
hypertrophic cardiomyopathy.
-
Radiographs- in cats with Dilated cardiomyopathy,
the heart is often very large on the x-ray. Since most cats present in
heart failure, fluid densities can be seen in and around the
lung fields.
-
ECG or electrocardiogram-same parameters as with
hypertrophic cardiomyopathy
-
Echodardiogram- shows a big floppy dilated heart
that has minimal ability to contract. Doppler probe measures the severity of
the murmur.
|
| Treatment |
| There is a wide variety of heart
medications available (most of which are used to treat disease in humans),
and treatment is based on the individual animal. All cats with DCM should
be immediately started taurine supplementation. Lasix or furosemide is a
diuretic used to help decrease the buildup on fluid in and around the lungs,
and eliminate extra sodium in the urine. Many other drugs can be used, most
on a temporary basis, to improve cardiac function. It is highly
recommended to consult a veterinary cardiologist. |
| Prognosis |
| Entirely dependent upon each individual but generally
guarded to poor prognosis for long term survival. With proper
therapy, some cats do well for years. Other cats do not respond to
medication and die quickly in heart failure. |
|
