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          Canine Cardiomyopathy          

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Dilated 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 collapse.


What is Cardiomyopathy?
DCM in Dogs
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What is cardiomyopathy?

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related terms: dilated cardiomypathy, Doberman cardiomyopathy, boxer cardiomyopathy
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 infections. 
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 extensive changes in the heart muscle and serious rhythm abnormalities, but without 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 this breed.

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 enlargement.

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 progressively 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 dog 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 (particularly 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 way 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 heart failure is present. If your dog has an abnormal heart rhythm without any evidence 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.

Breeding advice
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.  
FOR MORE INFORMATION ABOUT THIS DISORDER, PLEASE SEE YOUR VETERINARIAN.
Resources
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., Toronto.
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 Association.
Copyright © 1998 Canine Inherited Disorders Database. All rights reserved.Revised: December 15, 2000.
reprinted with kind permission from:-
 Alice Crook, DVM,Coordinator, Sir James Dunn Animal Welfare Centre, Atlantic Veterinary College,University of Prince Edward Island, 550 University Ave.Charlottetown, PEI C1A 4P3
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Dilated Cardiomyopathy (DCM) in Dogs

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Affected Animals
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 breeds.

Overview
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 blood flow to the rest of the body, DCM also can result in weakness, fainting, and exercise intolerance. Abnormal heart rhythms, or arrhythmias, frequently accompany DCM, and can complicate the treatment of dogs with this disease.

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.

Clinical Signs
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.

Symptoms
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 breath, rapid, shallow breathing, difficulty resting comfortably at night, and coughing.

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 exhibit signs 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 output is severely reduced.

Description
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 the name implies, the heart chambers are usually dilated or enlarged, and the heart muscle itself is usually thin and weak, contracting with much less vigor than normal. The term cardiomyopathy literally means "sick heart muscle."

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. When the heart muscle fails, pressures can increase and ultimately lead to left- or right-sided heart congestive heart failure. Reduced output from 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 Doberman pinschers. The development of an atrial arrhythmia called atrial fibrillation 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 these goals include diuretics, digoxin, and angiotensin converting enzyme inhibitors. Supplementation with substances such as taurine or l-carnitine may be helpful for some dogs with DCM.

Diagnosis
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 an extra heart sound called a gallop rhythm, or a soft heart murmur. Arrhythmias can be detected while listening to the heart with a stethoscope and while feeling for the pulse or heartbeat. Abnormal lung sounds are heard in dogs with left-sided heart failure, while distention or pulsation in the jugular veins, liver enlargement, or abdominal fluid accumulation may be present in dogs with right-sided heart failure. In addition, laboratory results may indicate mild changes in serum protein concentrations, sodium and potassium levels, liver enzymes, and mild increases in serum urea nitrogen and creatinine 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 disease. Heart enlargement and blood vessel changes consistent with heart failure 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 detected.

Prognosis
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 diagnosed with DCM before serious complications have developed may be able to live longer with treatment.

Transmission or Cause
There appears to be a strong association between breed and DCM. Infectious diseases, including Lyme disease, bartonellosis, and trypanosomiasis, have been reported in association with DCM and are usually accompanied by other symptoms.

Treatment
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 chronic settings.

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 contract, 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 muscle carnitine deficiency is difficult, and the appropriateness of supplementation with l-carnitine for all dogs with DCM is unknown, such supplementation is not known to be harmful. L-carnitine supplementation can be considered 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.

Prevention
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 that could pass DCM on to their offspring.
Reprinted with kind  permission from Roger Ross DVM,
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Dilated Cardiomyopathy
 DCM
 Cardiomyopathy Supplements

Hypertrophic Cardiomyopathy
 HCM


chloebutton  talabutton  

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.