Dilated Cardiomyopathy – by Petplace Veterinarians
Dilated cardiomyopathy (DCM) is a disease characterized by dilation or
enlargement of the heart chambers and markedly reduced contraction. The
left ventricle is most always involved. Advanced cases demonstrate dilation of
DCM is very common in dogs, representing the most common reason for
congestive heart failure (CHF). This heart disease also can cause heart valve
leakage causing heart murmurs or abnormal electrical activity of the heart-
producing arrhythmias (irregular or abnormal heartbeats). Large and giant
breed dogs, especially males, are predisposed. Doberman pinschers, Irish
wolfhounds, Scottish Deerhound, boxer, Afghan hound, Old English Sheepdog,
Great Danes, Dalmatians, Newfoundlands, and Saint Bernards are common
breeds. English and American cocker spaniel breeds and Portuguese water
The clinical condition of canine DCM can range from overtly healthy (occult
disease) to severe heart failure. Some dogs experience primary electrical
disturbances (arrhythmia) such as atrial fibrillation or ventricular tachycardia.
The disease is thought to be genetic in Doberman pinschers, Irish wolfhounds,
Newfoundlands, boxers, and Portuguese water dogs. The disease is
sometimes seen in Dalmatians fed a low protein diet and in cocker spaniels
and gold retrievers with taurine deficiency.
The average age of onset is 4 to 10 years, although Portuguese water dogs
can acquire the disease when very young.
DCM is very serious and the mortality rate, even of treated cases, is very
The advent of these problems should alert you that a serious emergency is at
Diagnostic tests are needed to recognize dilated cardiomyopathy and exclude
• Complete medical history and physical examination including auscultation of
• Packed cell volume test or a complete blood count (CBC)
• Serum biochemistries, which are blood tests that are especially important if
there is heart failure, thromboembolism or complications in other organs
• Echocardiogram (ultrasound of the heart) to establish the diagnosis and
• In advanced cases leading to congestive heart failure, drug therapy with a
diuretic, angiotensin converting enzyme inhibitor (such as enalapril or
benazepril and/or digoxin is prescribed.
The diet is changed to reduce sodium intake. Additional drugs may be added
such as the diuretic/hormone antagonist, spironolactone. Nutraceuticals such
as taurine pills or L-carnitine are recommended in very specific instances.
• In cases of "arrhythmogenic" dilated cardiomyopathy, drugs that regulate
the electrical heart rhythm are indicated.
• In "occult" dilated cardiomyopathy (healthy dog with early DCM diagnosed
by echocardiography), an angiotensin converting enzyme inhibitor drug and
possibly a beta-blocker drug is recommended to protect the heart muscle
• Administer any veterinary prescribed medications.
• Watch for difficulty in breathing, increase in coughing, lethargy or sudden
inability to use one or more limbs. Observe the breathing rate when your pet
• Schedule regular veterinary visits to monitor the condition.
DCM is thought to be the result of diverse processes that affect heart muscle
cell function. The vast majority of cases of DCM are idiopathic, which means
they have no known cause and are probably predisposed by genetic factors.
• Deficiency of metabolic substrates (taurine)
• Myocarditis (inflammation of the myocardium)
• Severe global myocardial ischemia (lack of blood supply to the heart)
• Toxic injury to the heart muscle cells that can be caused by some drugs like
doxorubicin or potassium iodide toxicity
• Persistently abnormal heart rhythms such as sustained ventricular or
• Chronic hypokalemia (low blood potassium)
A number of other diseases can be easily confused with dilated
cardiomyopathy unless an appropriate diagnostic evaluation is completed.
Diagnostic tests should help exclude the following conditions from
• Congenital heart diseases (birth defects)
• Hypertensive heart disease (heart enlargement from high blood pressure)
• Pericardial diseases (the lining around the heart)
• Mediastinal masses (tumors in the front part of the chest cavity)
• Myocarditis (inflammation of the heart muscle - a most difficult condition to
• Moderate to severe anemia (anemia can cause heart failure)
• Fever (fever can result in a heart murmur)
A complete medical history should be obtained and your veterinarian should
complete a thorough physical examination. Medical tests are needed to
establish the diagnosis, exclude other diseases, and determine the impact of
this disorder on your pet. The following diagnostic tests are often
• A thorough physical examination. Special attention is paid to auscultation
(stethoscope examination) of the heart. Heart murmurs, abnormal heart
sounds, and irregular heart rhythms may indicate a problem with the heart.
• Thoracic radiographs. X-rays of the chest identify heart enlargement and
• An electrocardiogram (EKG). While this test is often abnormal in cases of
serious heart disease, it can be normal in many other pets with heart disease.
• An echocardiogram. An ultrasound examination of the heart is required for
Important examination issues include the size of the heart and the ability of
the ventricle to contract. This examination may require referral to a specialist.
Your veterinarian may recommend additional diagnostic tests to exclude or
diagnose other conditions, or to understand the impact of dilated
cardiomyopathy on your pet. These tests insure optimal medical care and
• Complete blood count (CBC). This blood test may be needed to identify
anemia or other problems such as infections or inflammations.
• Serum biochemistry tests. This blood test is especially important if there is
heart failure or complications in other organs.
• Taurine concentrations may be determined from a blood sample.
• Urinalysis to evaluate kidney function
• Heartworm test if prevention has not been given
The principles of therapy depend on the presentation or current condition of
the pet. If symptoms are severe, hospital therapy is necessary. Precise
treatments depend on the problems caused but may include: treatment of
congestive heart failure, control of an arrhythmia or abnormal heart rhythms,
management of kidney failure, treatment of low blood pressure or shock
caused by severe heart failure, or treatment of complications of thrombosis
• Hospital treatment of severe congestive heart failure includes oxygen, the
diuretic furosemide (Lasix®), and often nitroglycerin or nitroprusside. If blood
pressure is low or heart function very bad, the drug dobutamine, which is a
stimulant of heart contraction, is often recommended for 24 to 72 hours.
Therapeutic thoracocentesis taps accumulated fluid from the chest cavity to
improve breathing, and is the best treatment for a large pleural effusion (fluid
• When present, chronic congestive heart failure (CHF) is managed with drug
therapy, including a diuretic, pimobendan angiotensin converting enzyme
inhibitor, such as enalapril or benazepril ,and digoxin. Beta-blocker drugs such
as carvedilol , metoprolol or atenolol is also used to help minimize
• The diet is changed to reduce sodium intake.
• Nutriceuticals like taurine pills, L-carnitine , and/or Omega-3 fatty acids are
• In cases of arrhythmogenic dilated cardiomyopathy, drugs that regulate the
electrical heart rhythm are indicated. If atrial fibrillation is present, digoxin
often combined with either a beta blocker or a calcium channel blocker drug is
• The dog with "occult" dilated cardiomyopathy is healthy, but has been
diagnosed with early DCM by echocardiography. There is evidence that an
angiotensin-converting enzyme inhibitor drug can protect the heart muscle
from further damage and enlargement. The drugs enalapril (Enacard) and
benazepril are the most often used for this purpose. A beta-blocker drug is
also effective in preventing further heart muscle damage, but must be chosen
Optimal treatment for your pet with dilated cardiomyopathy requires a
combination of home care and professional veterinary care. Follow-up can be
critical. Administer prescribed medication and alert your veterinarian if you
are experiencing problems treating your pet. Optimal follow-up care often
• Administering prescribed medications. Remember – erratic administration of
medication is a common reason for treatment failure.
• Observe your pet's general activity level, appetite, and interest. These are
quality-of-life issues of importance to you and your pet.
• Watch your pet for labored or rapid breathing or for coughing. If possible,
learn to take a breathing rate when your pet is resting. Ask your veterinarian
• Follow-up chest X-rays may be required to monitor the response to therapy.
• A blood digoxin test is done approximately 7 to14 days after initiation of
therapy to identify therapeutic vs. toxic drug levels.
• Blood chemistry is checked periodically to monitor the effects of drugs on
the kidneys and electrolytes like potassium. If kidney values or electrolytes
are abnormal, the dose of diuretic must often be lowered.
• Arterial blood pressure measurements should be checked periodically.
• An echocardiogram should be done initially and repeated periodically (3 to 6
months after diagnosis and again in 9 to 12 months). Some dogs experience
improvement though most show progression of heart muscle disease.
• Of course, the precise follow-up depends on the severity of your dog's
disease, response to therapy, your veterinarian's recommendations, and your
The prognosis for dogs with DCM is guarded. From diagnosis, the average
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