What is Cardiomyopathy?
cardiomyopathy - A disease of the heart muscle that results in weakened
contractions and poor pumping ability. As the disease progresses
the heart chambers become enlarged, one or more valves may leak and
signs of heart failure develop. Signs of DCM include reduced
exercise tolerance, increased breathing rate and panting, coughing,
swollen abdomen, loss of appetite and in progressed cases the dog may
DCM in Dogs
Cardiomyopathy refers to
disease of the heart muscle (the myocardium) without malformation of
the heart or its valves. There is a breed predisposition to dilated
cardiomyopathy in giant breeds, as well as in Doberman pinschers and
boxers. Cardiomyopathy can also develop as a result of some toxins or
related terms: dilated cardiomypathy, Doberman cardiomyopathy, boxer
There are 3 types of cardiomyopathy:
dilated cardiomyopathy. This is by far the most common type in
the dog. There is dilation of the chambers of the ventricles of the
heart with some increase (hypertrophy) in the heart muscle mass, and a
loss of the normal contracting abilities of the ventricles.
hypertrophic cardiomyopathy. In this form of cardiomyopathy,
there is a tremendous increase in the mass of the heart muscle in the
ventricles, with a resultant decrease in chamber size. Relatively few
cases of hypertrophic cardiomyopathy in dogs have been reported, and no
significant breed predisposition has been identified. Most of the dogs
affected have been male.
restrictive. This type has not been reported in dogs.
The heart works harder to compensate for the loss of contractility,
eventually leading to congestive heart failure. The abnormalities in
the heart muscle cells give rise to irregular heart rhythms which may
cause sudden death.
How is cardiomyopathy inherited?
The pattern of inheritance is not known.
What breeds are affected by cardiomyopathy?
Dilated cardiomyopathy is seen more often in Doberman pinschers than in
all other breeds combined. It also occurs in giant breed dogs including
the Great Dane, St. Bernard, Irish wolfhound, and Scottish deerhound.
A distinctive form of cardiomyopathy occurs in the boxer, with
changes in the heart muscle and serious rhythm abnormalities, but
the dramatic dilation of the ventricles seen in other breeds.
Dilated cardiomyopathy is also seen in English cocker spaniels. In all
breeds affected, it is more common in males.
For many breeds and many disorders, the studies to determine the mode
of inheritance or the frequency in the breed have not been carried out,
or are inconclusive. We have only listed breeds for which there is a
strong consensus among among those investigating in this field and
among veterinary practitioners, that the condition is significant in
What does cardiomyopathy mean to your dog & you?
Giant breeds with dilated cardiomyopathy typically show signs
associated with abnormalities of heart rhythm (particularly atrial
fibrillation) and generalized heart failure. These signs may include
weakness, loss of appetite, weight loss, depression, episodes of
collapse, respiratory difficulties, a soft cough (especially at rest),
and an enlarged abdomen. There is severe enlargement of all 4 chambers
of the heart. Dogs are affected in middle-age on average, although they
may be affected as early as a few months of
age. Abnormalities may be seen on an electrocardiogram before there are
any clinical signs.
In addition to signs of heart failure as outlined above, a distinctive
feature of this disorder in Doberman pinschers and boxers is that the
abnormal heart rhythms that are seen originate most commonly in the
ventricles, and are quite serious. As well, Dobermans often have left
atrial rather than
generalized enlargement of the heart and boxers may show no heart
In Doberman pinschers there is a relatively long period of 2 to 4
years without clinical signs of illness ( the "occult" phase), during
which changes occur in the heart muscle and rhythm disturbances
worsen. Sudden death occurs in about 25% of these dogs. Others will go
on to develop congestive heart failure. Weight loss is often sudden and
dramatic in these dogs. Death usually occurs fairly soon after clinical
signs develop, often within 6 months.
In boxers, there are 3 distinct stages of cardiomyopathy:
Stage I. An irregular heart rhythm is discovered incidentally
during a routine examination, or examination for other purposes. The
has no clinical signs of illness.
Stage II. These dogs are examined because of intermittent
episodes of collapse or weakness. On examination, an abnormal heart
rhythm (generally originating in the ventricles) is found.
Stage III. These dogs show signs of heart failure which may
include weakness, depression, exercise intolerance, a soft cough
at rest or at night), a loss of appetite, weight loss which may be
dramatic, and fainting or collapse.
The episodes of fainting, collapse, or weakness are generally due
to abnormal rhythms in the heart, because of the damaged heart muscle.
For this reason, regular monitoring by electrocardiogram is the best
of assessing the progression of cardiomyopathy in these dogs. Dogs in
either of the first stages may develop heart failure at any time.
For all dogs with dilated cardiomyopathy, the arrhythmias that can
cause fainting or collapse can also cause sudden death. Up to 50% of
affected dogs die suddenly, often without having shown any other signs
of the disorder.
Once dogs with cardiomyopathy develop congestive heart failure, the
prognosis is poor.
How is cardiomyopathy diagnosed?
X-rays generally show an enlarged heart, predominantly on the
left side. Boxers may show no abnormalities on radiographs.
In both Dobermans and boxers with cardiomyopathy, there may be no
abnormalities on radiographs, on physical exam, or on the resting
electrogardiogram. If cardiomyopathy is suspected and all routine
diagnostic tests are normal, a 24 hour ambulatory electrocardiogram ( a
Holter monitor) is recommended. The unobtrusive monitor is worn by the
dog during its normal activities, and records irregular heart rhythms.
FOR THE VETERINARIAN:
RADIOGRAPHS:see generalized cardiomegaly with left atrial and
ventricular enlargement predominating. In Dobermans, only left
atrial enlargement may be evident. In boxers, thoracic radiographs may
be normal, or there may be mild to moderate cardiomegaly.
ELECTROCARDIOGRAM: atrial fibrillation is seen in 75 to 80
per cent of giant-breed dogs with dilated cardiomyopathy. There may be
subtle changes such as high amplitude or widened QRS complexes (left
ventricular enlargement), or widened P waves (left atrial enlargement).
In Dobermans and boxers, one sees ventricular premature
contractions of variable frequency, singly or in runs, and, later,
paroxysms of ventricular tachycardia.
ECHOCARDIOGRAM: reduced contractility, ventricular dilation (may
not be seen in boxers).
PHYSICAL EXAM: occasional to frequent premature beats, pulse
deficits, paroxysmal tachyarrhythmias or a totally irregular
ventricular rhythm, variability in femoral pulse strength.
How is cardiomyopathy treated?
Decisions about treatment are based on several factors: whether the dog
is showing clinical signs such as weakness or collapse, what
arrhythmias are seen on the electrocardiogram, and whether congestive
is present. If your dog has an abnormal heart rhythm without any
of congestive heart failure, your veterinarian may prescribe
anti-arrhythmic drugs, depending on the severity of the arrhythmia.
Episodes of collapse indicate a serious arrhythmia and must be treated
as an emergency.
Treatment for dogs with signs of congestive heart failure involves
rest, diet restrictions, and drugs to stabilize and support the failing
heart as well as to control the arrhythmias. If low doses of
anti-arrhythmic drugs are effective, then the heart can often be
stabilized. Serious ventricular arrhythmias that can only be controlled
by high doses of anti-arrhythmic drugs have a poorer prognosis.
New treatments are being used in Dobermans and boxers with
cardiomyopathy in an attempt to delay the onset of congestive heart
failure or sudden death.
Affected individuals and their parents should not be used for
breeding. Siblings should only be used after careful screening.
How can cardiomyopathy be controlled?
There are ways to approach the control of this disease. Although signs
of heart failure are often not evident until middle age, abnormalities
on the electrocardiogram are often apparent earlier. In affected breeds
with a family history of cardiomyopathy and in ALL Doberman pinschers,
breeding animals should be evaluated yearly for evidence of cardiac
arryhthmias, using an ambulatory (Holter) monitor if possible. Dogs in
which occult dilated cardiomyopathy has been identified (ie. no
clinical signs) should not be used for breeding.
INFORMATION ABOUT THIS DISORDER, PLEASE SEE YOUR VETERINARIAN.
Calvert, C.A. 1995. Diagnosis and management of ventricular
tachyarrhythmias in Doberman pinschers with cardiomyopathy.
In R.W. Kirk and J.D. Bonagura (eds.), Current Veterinary
Therapy XII Small Animal Practice, p. 799-806. W.B. Saunders Co.,
Jacobs, G. 1998. Comprehensive update on Doberman
cardiomyopathy. ACVIM-Proceedings of the 16th Annual Veterinary
Medical Forum: 107-109.
Meurs, K.M., Brown, W.A. 1998. Update on boxer
cardiomyopathy. ACVIM-Proceedings of the 16th Annual Veterinary
Medical Forum: 119-120.
Copyright © 1998 Canine Inherited
Disorders Database. All rights reserved.Revised: October 30, 2001.
This database is funded jointly
by the Animal Welfare Unit at the Atlantic Veterinary College,
University of Prince Edward Island, and the Canadian Veterinary Medical
Copyright © 1998 Canine
Inherited Disorders Database. All rights reserved.Revised: December 15, 2000.
with kind permission from:-
Crook, DVM,Coordinator, Sir James Dunn Animal Welfare Centre, Atlantic
Veterinary College,University of Prince Edward Island, 550 University
Ave.Charlottetown, PEI C1A 4P3
Dilated Cardiomyopathy (DCM) in Dogs
The dogs most frequently diagnosed with DCM are large and giant
purebred dogs, including Scottish deerhounds, Doberman pinschers,
boxers, Saint Bernards, Afghan hounds, Newfoundlands, and old English
sheepdogs. Recently, both English and American cocker spaniels have
been diagnosed more frequently with DCM than other small breed dogs.
Most dogs with DCM are older, as the prevalence of DCM increases with
age. Male dogs are affected more commonly than female dogs for most
The term cardiomyopathy literally means "sick heart muscle".
Dilated cardiomyopathy, or DCM, occurs when the heart muscle is thin,
weak, and does not contract properly. DCM most commonly affects large
or giant purebred dogs, but it also can be seen in smaller breeds such
as cocker spaniels, and in mixed breed dogs. The condition can lead to
congestive heart failure, in which fluid accumulates in the lungs, the
chest or abdominal cavities, or under the skin. Because of reduced
flow to the rest of the body, DCM also can result in weakness,
and exercise intolerance. Abnormal heart rhythms, or arrhythmias,
accompany DCM, and can complicate the treatment of dogs with this
In rare cases, supplementation with substances such as l-carnitine or
taurine may dramatically reduce signs in individual patients, but for
most dogs, the main goals of treatment are to lessen signs due to
congestive heart failure and to attempt to improve the heart's ability
to pump blood. The long-term outlook for dogs with DCM is usually quite
poor, and most dogs with DCM eventually die from the disease. Despite
the poor long-term outlook, however, many dogs with DCM can benefit
from medical treatment that helps control symptoms.
Signs may be consistent with right heart failure, left heart failure,
or both. Right heart failure signs can include abdominal distention due
to ascites, jugular venous engorgement or pulsation, hepatomegaly,
pleural effusion, edema, pericardial effusion, and weight gain due to
fluid retention. Left heart failure signs can include cough due to
pulmonary edema, shortness of breath, tachypnea, and dyspnea. Some
signs can be seen with right or left sided heart failure, including
fatigue and weakness, exertional dyspnea, gallop rhythm, pallor,
increased capillary refill time, cyanosis, cool
extremities, and weight loss.
Dogs with dilated cardiomyopathy can show symptoms due to right-sided
congestive heart failure including abdominal enlargement; distention of
the veins in the neck or other parts of the body; and fluid
accumulation in the abdomen or chest, in the sac around the heart or
underneath the skin, especially in the legs and on the underside of the
body. This fluid retention can lead to weight gain. Other dogs will
show evidence of lung problems
due to left-sided congestive heart failure, including shortness of
rapid, shallow breathing, difficulty resting comfortably at night, and
It is also common for dogs with DCM to show signs of both right and
left heart failure. These signs can include weakness and exercise
intolerance, and difficulty breathing with increased activity. Weight
loss is common in dogs with DCM that do not retain fluid. Some animals
due to reduced blood flow to tissues, including pale mucous membranes,
bluish color to the mucous membranes, and cold feet and legs. Fainting
may occur if abnormal heart rhythms are present, or if the heart's
is severely reduced.
Heart failure occurs when the blood returning to the heart from the
rest of the body cannot be pumped out fast enough to meet the demands
of body tissues. Heart muscle disease is one of the potential causes of
heart failure. Dilated cardiomyopathy is a condition characterized by a
variety of changes in the heart muscle that result in pump failure. As
implies, the heart chambers are usually dilated or enlarged, and the
muscle itself is usually thin and weak, contracting with much less
than normal. The term cardiomyopathy literally means "sick heart
The primary abnormality occurring with DCM is impaired function of the
ventricles due to decreased strength of the heart muscle. The left
ventricle pumps blood from the lungs to the rest of the body, and the
right ventricle pumps blood from the rest of the body to the lungs.
the heart muscle fails, pressures can increase and ultimately lead to
left- or right-sided heart congestive heart failure. Reduced output
the heart may result in signs such as weakness, exercise intolerance,
fainting, and shock. Heart valve insufficiencies, abnormal heart
rhythms or arrhythmias, and the results of the body's compensatory
responses to reduced heart
muscle performance can compound the problems seen with DCM. Ventricular
arrhythmias can often lead to sudden death, especially in boxers and
pinschers. The development of an atrial arrhythmia called atrial
can have important short-term and long-term consequences for dogs with
DCM. This arrhythmia can be seen in all breeds of dogs.
Medications are used to treat the consequences of heart muscle failure,
to attempt to improve the heart muscle's ability to contract, and to
normalize or improve rhythm disturbances. Drugs used to accomplish
include diuretics, digoxin, and angiotensin converting enzyme
Supplementation with substances such as taurine or l-carnitine may be
helpful for some dogs with DCM.
The diagnosis often is first suspected when symptoms compatible with
DCM are present in a large or giant purebred dog or cocker spaniel.
Physical examination abnormalities frequently include the presence of
heart sound called a gallop rhythm, or a soft heart murmur. Arrhythmias
can be detected while listening to the heart with a stethoscope and
feeling for the pulse or heartbeat. Abnormal lung sounds are heard in
with left-sided heart failure, while distention or pulsation in the
veins, liver enlargement, or abdominal fluid accumulation may be
in dogs with right-sided heart failure. In addition, laboratory results
indicate mild changes in serum protein concentrations, sodium and
levels, liver enzymes, and mild increases in serum urea nitrogen and
levels, or kidney values.
Although they will not always reveal major changes, chest x-rays
should always be evaluated in patients suspected of having heart
Heart enlargement and blood vessel changes consistent with heart
may be seen, and fluid accumulation in or around the lungs can be
identified if heart failure has developed.
The most definitive diagnostic test for DCM is the echocardiogram, an
ultrasound evaluation of the heart. Heart chamber dilation and
enlargement, reduced heart muscle wall thickness, and decreased heart
muscle wall movement are the hallmarks of DCM. In addition, mild heart
valve abnormalities may be seen. Doppler echocardiography may be used
to assess the severity of valvular abnormalities based on changes in
blood flow through the heart.
The electrocardiogram may identify abnormal rhythms or changes in the
normal tracings. The most common rhythm disturbance occurring with DCM
is atrial fibrillation, a condition characterized by a tremendous
increase in the rate of contraction of the atria, the uppermost
chambers of the heart, coinciding with an increased rate of contraction
of the ventricles, the lower and larger chambers of the heart. Other
rhythm disturbances, including premature ventricular beats, may be
Currently, DCM is almost always fatal. Most dogs die within six to 24
months after being diagnosed. Severely ill dogs often do not survive
the first two days in the hospital. Doberman pinschers may have a worse
prognosis compared to other breeds. However, the response to treatment
will vary for any individual dog. Treatment should always be attempted
before rendering a prognosis. As with almost any disease, dogs
with DCM before serious complications have developed may be able to
longer with treatment.
Transmission or Cause
There appears to be a strong association between breed and DCM.
Infectious diseases, including Lyme disease, bartonellosis, and
have been reported in association with DCM and are usually accompanied
by other symptoms.
DCM generally is not curable, and spontaneous recovery is unlikely. The
primary goals of treatment are to lessen clinical signs of heart
failure and to prolong survival. Treatment of an individual dog is
dictated by the severity of its signs at the time of diagnosis, and the
presence or absence of changes such as congestive heart failure and
arrhythmias. The primary drug to reduce fluid accumulation secondary to
congestive heart failure
is furosemide, marketed as Lasix. It can be used to treat acute,
life-threatening fluid accumulation or to control and prevent
congestive abnormalities in
Digoxin is used for several reasons in the treatment of DCM. It may
help increase the heart's ability to contract and slow down the
ventricular response rate in dogs with atrial fibrillation. Digoxin
also blunts some of the neurological and hormonal responses to heart
failure that lead
to worsening of the condition. Drugs such as dobutamine, amrinone, and
milrinone may be used to increase the heart muscle's ability to
but they are indicated primarily for short-term emergency situations.
Recently, the use of drugs called angiotensin converting enzyme,
or ACE, inhibitors has been shown to benefit dogs with DCM by reducing
the signs due to heart failure and improving exercise tolerance.
ACE-inhibitors have many effects, including blood vessel dilation,
which reduces the resistance the heart has to pump against. The drug
also remodels the diseased heart muscle. Other types of blood vessel
dilators can be used in the short-term or long-term treatment of DCM to
reduce the load that the heart has to
pump against to get blood to flow.
Other drugs control heart rhythm disturbances. Digoxin is commonly used
in dogs with atrial fibrillation. Other anti-arrhythmic drugs,
including procainamide, marketed as Procan, and mexiletine, marketed as
Mexitil, are used for dogs with ventricular arrhythmias due to DCM.
L-carnitine is a compound that plays an important role in fatty acid
metabolism and in neutralizing potential toxins in cells. Carnitine
deficiency in the heart muscle has been shown to be potentially
reversible in at
least one family of boxers with DCM. Although the diagnosis of heart
carnitine deficiency is difficult, and the appropriateness of
with l-carnitine for all dogs with DCM is unknown, such supplementation
is not known to be harmful. L-carnitine supplementation can be
for all dogs with DCM.
Another substance that may play a role in the treatment of DCM,
particularly in cocker spaniels, is taurine. Taurine deficiency was
found to be the most important factor associated with DCM in cats in
the 1980's, and correction of cat food formulations to eliminate
taurine deficiency resulted in
the almost complete elimination of DCM as a major heart muscle disease
in cats. However, the exact role of taurine in the treatment of DCM in
dogs remains undetermined. Other substances, such as coenzyme Q-10, may
also play a role in the treatment of this disease.
Affected dogs should not be bred. Early screening of dogs of breeds
that have a high incidence of DCM may help identify important changes
prior to the onset of signs. This can help prevent the breeding of dogs
could pass DCM on to their offspring.
Reprinted with kind
permission from Roger Ross DVM,
The above information is simply
informational. It's intent is not to replace the advice of a
veterinarian nor to assist
you in making a diagnosis of your pet. Please consult with your own
veterinarian for confirmation of any diagnosis. Your pets life may
depend on it.