Cardiac Diseases & Conditions - Explained
Just like their owner, the heart of our pet is often the first thing that wears out. But our pets
do not develop plaques in the blood vesicles of their heart (arteriosclerosis, coronary artery
disease) so they do not get the heart attacks we do.
Like al mammals, dogs and cats have a four-chambered heart. It consisting of a left and
right upper chambered atrium and a left and right lower chambered ventricle.
The left and right atria receive blood from the lungs and body respectively. The left ventricle
is responsible for pumping oxygen-rich blood from the lungs out through the aorta into the
body, while the right ventricle pumps the blood through the pulmonary artery to the lungs for
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the mitral valve. The one between the right atrium and ventricle is the tricuspid valve. The
one regulating blood going into the aorta is the aortic valve and the one regulating blood
going to the lungs is the pulmonic valve.
The mitral valve is the most fragile of the four valves in your pet's heart. In dogs, it is often
What Signs Would I See If My Pet Had A Heart Problem?
The first sign that most owners notice is a cough. this is because enlarged, failing hearts
al ow fluid to back up into the lungs and also press on the wind pipe.
Other signs you may notice in your pet are tiredness, rapid breathing, poor appetite, an
enlarged tummy, pale or bluish gums, and a rapid, weak pulse. Fainting is less common.
What Might My Veterinarian Hear Through A Stethoscope?
Many of these pets have heart murmurs. Heart murmurs come about when a passage
through the heart becomes too narrow or too wide. In middle aged or older adult cats and
dogs, this usual y means that a valve is not working properly. It may not be closing
sufficiently or it may not be opening sufficiently. In younger pets, a murmur might mean that
Anemic pets develop heart murmurs because their blood is too thin - not because of an
The rhythm of a weakened heart also changes. But unlike us, frequent changes in the heart
What Tests Might My Veterinarian Perform?
If your veterinarian is suspicious that your dog might have a heart problem, the first test we traditional y do is an x-ray. If the x-ray shows an enlarged heart, your veterinarian may be
satisfied with that and begin treatment.
If it is unclear if the heart is enlarged or if the heart is even the source of your pet's
problems, amight be ordered. This test is especial y useful in cats when we
are not sure if the cat has a lung problem, asthma or a heart problem.
Other tests that your veterinarian or a cardiac specialist might perform are echocardiograph
(doppler ultrasound) to see the heart perform in real time, and an EKG to check if the
electrical system of the heart is functioning normal y.
What Are Some Of The Effects Of A Failing Heart?
In dogs, the valves are often the first heart structures that are affected. Heart disease in cats
usual y involves the entire heart muscle and not just the valves.
Dogs let us know early that there is a problem. But we are often unaware that our cat has a
heart problem until its heart is wel on its way to failing. Often the only signs in your cat are
weight loss, and difficulty breathing. Cats are more likely to make asthmatic-like sounds
Cats with this form of heart disease do not survive long. Signs of al forms of heart disease
in cats are quite similar and your veterinarians wil not be able to tell one from the other
In al cases of heart disease in dogs and cats, as the circulatory system fails, the kidneys
liver and all other organs are flooded with stagnant blood and work inefficiently. This is
because they do not get the oxygen they need.
Heart Problems That Affect Both Dogs And Cats:
The heart is like your car's motor. If one part goes out, it is not long before it causes another
part to fail. So in reality, most actual cases of heart disease are a combination of several
problems. The normal heart has a very precise shape. As its shape expands and becomes
more rounded, the heart is not able to perform any of its tasks wel .
Congestive Heart Failure (CHF):
Congestive heart failure is an enlarged heart. No matter what the underlying heart problem
CHF occurs when the heart is unable to meet the circulatory demands of the body. Many
things can cause the heart to be faced with increased back pressure and decreased
effectiveness as a pump. Valvular defects, tumours, heartworms, heart beat abnormalities,
and damaged to the muscle itself al cause the heart to enlarge and blood to pool in the
organs and lungs. The net effect of al this is cal ed congestive heart failure.
All pets with CHF have an enlarged heart. As the disease progresses, the normal triangular
shape of the heart becomes rounded. This is very noticeable on an x-ray. An x-ray or a
cardiac ultrasound is the way your veterinarian wil confirm CHF.
Since CHF is a common human problem, drugs are constantly being developing and
refining to treat it. These human medications work quite wel in our pets too. So your
veterinarian may be using a drug I have not mentioned. This is particularly the case if you
visit a veterinary cardiologist. However, it is uncertain if these newer human medications
extend the life of your pet any more than those that are more commonly used by your local
Veterinarians treat CHF with several medication groups at once:
We remove as much pooled fluids and blood as we can with drugs cal edOnce
these fluids are removed from your pet's lungs, the cough should go away or be much
better. The big pot-bel y associated with CHF should also go away. The most commonly
When furosemide wil no longer remove enough fluid from your pet, we often add a second
Do not be surprised when your pet drinks and urinates more on these medications.
We also increase the diameter of blood vessels throughout the body with vasodilator drugs
so the heart does not have to work as hard. Most of the medicines of this group are
calledThe most common ones in this group are Benazapril (Forticor).
By making it easier for blood to flow through blood vessels, ACE inhibitors help decrease
your pet's heart rate, and help preserve the heart's remaining strength. The most common
side effect of these drugs is lack of appetite and vomiting. If that occurs, the dose needs to
Inodilators are an exciting group of drugs that seem to definitely extend the lives of dogs
with CHF. The one most commonly used is calledVetmedin). It increases the
amount of blood that the weakened heart can pump by giving more strength to its muscle
fibers. It also opens up blood vessels throughout the body so the heart doesn't have to work
as hard. A study found that dogs receiving pimobendan and furosemide
onger than those receiving only enalpril / Benazapril and furosemide. It has been
used in cats, although it is not licensed for that species.
Another group of drugs we used when diuretics and ACE inhibitors were not enough are
called Positive ionotrophic agents. A drug in this group that was quite popular
isBecause of its potent side effects and the limited length of time pets wil survive
while on it, I rarely prescribe it. It is a medicine of last resort.
The heart has an electrical wiring system to coordinate it's contractions. When the heart is
damaged, this system may fail. We cal the abnormal beat rhythm a cardiac arrhythmia.
Some of the drugs used to control arrhythmias are propranolol (Inderal) procainamide
Many veterinarians suggest pets with heart disease consume a low sodium diet. This is a
particularly good idea if your pet also has elevated blood pressure or retained fluid. We do
not know if low sodium diets are as beneficial to pets as they are to humans.
Some veterinarians prescribe coenzyme Q because of its beneficial effects in people with
Omega-3 fatty acids are high in fish oil. In people, there isthat omega-3
supplements might reduce the risk of heart attacks and strokes. Based on this, some
veterinarians suggest that dogs with heart problems also receive them.
L-carnitine is involved in the process by which the heart muscle converts fats into energy.
There isthat L-carnitine supplements help people who have heart disease.
Whether or not it helps pets, we do not know.
There is a smal group of dogs and cats that develop heart disease due to a deficiency in
the amino acid, Taurine. Since it is non-toxic, some veterinarians suggest a taurine
supplement for al their cardiac patients.
Keep your pet's weight optimal and feed a name brand commercial diet.
In exercising your pet, keep activity to a level short of what it would take to cause your pet to
breath heavily, pant or elevate its heart rate. Don't give up short walks until you absolutely
must. Dogs and cats benefit physical y and mental y from activity.
Valvular Disease Of Dogs And Cats:
Certain breeds of dogs, particularly toy breeds, have a tendency to develop scaring heart valve problems or endocardiosis. This is the most common form of heart disease in dogs
Age-related scaring of the mitral valves is also quite common in al old dogs. The mitral
valve divides the lower and upper left chambers of the heart. It's constant hard work may cause it to fail to completely close and open. Sixty percent of dogs over 8 years old have
some degree of this problem. But less than half the dogs with this condition have any
Many veterinarians have noticed that smal breeds of dogs that eat soft food and table scraps eventual y develop chronic mouth infections or periodontal disease. It is very
common for these pets to also have a heart murmur related to their mitral valve. We think
that bacteria move from the infected gums through the blood and attach to the heart valves
to cause a condition cal ed endocarditis that eventual y scar the heart valves. However, a
When the mitral valve wears out, its two flaps become blunted, shrivel ed and scarred so
that they do not open or close properly. When this happens, blood does not flow in the
normal pattern but leaks back in to the atrium or ventricle.
With time, increased back pressure causes one or more chambers of the heart to enlarge.
As the chambers of the heart enlarge they press on the windpipe resulting in a dry, hacking
cough. The enlarged heart also stretches the nerve fibers that control heart rhythm resulting
in abnormal beats or arrhythmias. As blood backs up, it pools in the lungs as edema that
makes the cough even worse. Particularly when the pet is lying down or at rest.
Defective Heart Development:
Dogs and cats are sometimes born with heart disease. We cal this congenital disease.
This problem is most common in big dogs (Rotties, Boxers, Newfoundlands, Goldens, Great Danes etc.) It is the most common inherited heart disease in large dogs.
In sub-aortic stenosis the puppy is born with an abnormal y narrow passage way leading
from the heart to the aorta. It comes in all degrees, from a very mild case, requiring no
treatment to a life-endangering problem.
When you take a puppy to the vet for his first vaccinations, the veterinarian should listen to
the puppy's heart. In a puppy with SAS, there wil usual y be a heart murmur over chest
near the left base of the heart. If the puppy is not severely anemic with hookworms, then
SAS is the most common cause of the murmur. This is how most cases of SAS are first
diagnosed. Not every puppy with a heart murmur has SAS. Puppies often outgrow heart murmurs without our real y knowing what caused them in the first place. Only some
complicated tests can tel which murmur is important. But if your puppy stil has a murmur
when it is 6 months old, SAS becomes likely.
When a puppy has a significant degree of SAS, its heart has to work harder to force the blood through the narrow area just below the aortic valve. With time, the heart muscles get
thicker due to the extra effort. As the wal s thicken, the ful heart holds less and less blood
and needs more and more oxygen. Eventually, the heart begins to fail. Unlike older dogs
with CHF, SAS puppies often die suddenly when clots form in the heart muscle or its
Neither parent of an SAS puppy should ever be bred again.
Most often, you wil see no signs at al in your puppy. But as time goes by and the puppy's
heart muscles thicken, problems in the electrical system of the heart can cause fainting or
To decide how serious a heart murmur real y is, your pet needs to have an echocardiograpy
(doppler ultrasound) performed by a veterinarian experienced in interpreting the results. An
x-ray and an EKG wil also be required to see how much damage has already occurred.
The most popular drugs used to treat SAS are known as-blockers). The
most commonly used ones are Propranolol (Inderal) and atenolol (Tenormin). Beta blockers
reduce heart rate, help control abnormal heart rhythm and reduce blood pressure. They are
proven in their ability to extend the lives of dogs with SAS.
Open heart surgery to correct this problem in dogs has not been as successful as one might
hope. Dogs that have had the surgery, live about as long as dogs that just receive medicine.
This technique is similar to bal oon angioplasties that are done to dilate blocked coronary
arteries in people. A catheter is threaded into the heart and a bal oon is expanded in the
narrowed area of the heart. So far, this technique has not led to increased life span.
This is very difficult to predict. They younger the puppy is when the problem is first noticed,
and the louder the heart murmur, the bleaker the outlook. Most dogs with the typical signs of
SAS do not live over 3 years without medication.
A cardiac work-up at a regional veterinary centre that includes all the diagnostic tests, might
give you more insight. But al pets with this condition can die suddenly - and often do.
This problem was due to a deficiency in an amino acid, taurine. Now that we know that cats
must have sufficient taurine in their diet, al major brands of cat food have adequate taurine
Taurine deficiency caused the heart muscle to lose its strength. Cats with this problem lost
weight and had difficulty breathing. Blood clots often formed in the hearts of these cats.
A second, genetic form of the disease occurs in Siamese, Burmese and Abyssinian cats.
We treat this condition with the same medicines that increase the hearts efficiency and
decrease pooled fluid in the lungs. We also give them drugs to reestablish their normal
heart rhythm. Many veterinarians include a taurine supplement in any heart condition in
cats. A similar heart disease can also occur secondary to an over-active thyroid gland. Cats
with this problem wil not live very long.
In this disease the wal s of the heart thicken, leading to inefficient pumping of blood. Blood
pressure rises and fluid accumulates in the lungs. Eventual y the chambers of the heart
enlarge and abnormal heart rhythms occur. Signs of this disease are labored breathing,
rapid heart rate, heart murmurs, weakness, col apse and death. Rare heart valvular
disease, hyperthyroidism and asthma can mimic hypertrophic cardiomyopathy. We
diagnose this disease with x-rays electrocardiograms (EKG or ECG) and cardiac
We treat the disease with low salt diets, diuretics, aspirin to prevent blood clots, and
medications such as Diltiazem and atenolol to stabilize blood pressure and heart rate. Do
not give aspirin to your cat without veterinary supervision - cats do not handle aspirin wel .
In this condition localized scarring of the heart muscle prevents the normal beating of the
heart. This leads to an enlarged, weak heart and congestive heart failure. Signs of the
disease are poor appetite, weight loss and difficult respiration. Sometimes blood clots that
cause paralysis of the limbs occur. X-rays, EKG and ultrasound al show atrial enlargement. We treat these cats with calcium channel blockers such as diltiziam, diuretics such as
furosemide and low doses of aspirin. Aspirin must be used with extreme caution in cats. Do
so only under the supervision of a veterinarian. Low sodium diets might also help if the pet
wil eat them. If we are fortunate, cats with this disease live about a year.
In this condition, as in cats, the heart chambers enlarge to the point where they can no
longer pump blood efficiently. It is most common in large breeds of dogs and rare in smal
breeds. Doberman Pinschers, Great Danes, German Shepherds and Labrador Retrievers
are particularly at risk. The disease is most common in middle-aged dogs, especial y males.
Usual y the cause is unknown. However, we think that taurine deficiencies, parvovirus and
the use of adriamycin have al caused the disease.
The overly-stretched heart muscle that occurs in this disease is an inefficient pump. Signs of
the disease are those of congestive heart failure: difficult breathing, weakness, coughing
and fluid enlargement of the abdomen. These dogs may need oxygen until medicines have
an opportunity to work. Low salt diets as wel as supplements that contain taurine, L-
carnitine (carnatine) and coenzyme Q may also be helpful. Dogs do not survive long with
This disease is quite rare. As in cats, the muscles of the heart thicken and become
inefficient at pumping blood. The signs of the disease are the signs of congestive heart
failure e.g. difficulty breathing, coughing, heart murmurs and exercise intolerance.
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