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Diagnosing Dilated Cardiomyopathy and Screening Dogs for Heart Disease

How to Recognize Whether Your Dog Has DCM

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Heart Disease in Dogs Caused by Canine Dilated Cardiomyopathy

Dilated cardiomyopathy (DCM) is one of the most common heart diseases seen in large breed dogs. There are many tests used to screen dogs for DCM and to diagnose heart disease caused by DCM.
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Dilated cardiomyopathy is a disease that affects the muscle of the heart, effectively making the heart unable to contract efficiently.

Screening Dogs for Heart Disease Caused by Dilated Cardiomyopathy

One of the most common causes of dilated cardiomyopathy is a genetic mutation. As a result, screening a dog who belongs to a high risk breed is often desirable. The process is not as simple as it might sound, since evidence of the disease may not show up until later in life.

Unfortunately, the genetic mutation responsible for causing dilated cardiomyopathy is not the same in each breed. In some breeds, the mutation has been discovered and genetic tests are available to screen these breeds. Breeds in which genetic testing is available include Boxers and Doberman Pinschers. However, even in these breeds, a positive test for the mutated gene does not guarantee that the dog will develop disease.

In many breeds, the mutation has not been isolated and research is still ongoing. In these breeds, there is no genetic test.

A thorough physical examination by your veterinarian should be performed regularly and may reveal an abnormal heart beat (known as an arrhythmia). However, in many cases, the physical examination is completely normal.

Other types of screening depend on the breed and the type of dilated cardiomyopathy most likely to occur. For instance, in Boxers, a form of dilated cardiomyopathy known as arrhythmogenic right ventricular cardiomyopathy (ARVC) is known to exist. In this breed, using a Holter monitor for 24 hours is recommended as a screening test. (A Holter monitor is a device that measures the electrical activity of the heart on a continual basis while in use.) A Holter monitor is often recommended for Doberman Pinschers as a screening test as well.

An echocardiogram is another diagnostic test commonly used to screen for dilated cardiomyopathy. An echocardiogram is an ultrasonographic study of the heart. In dogs with dilated cardiomyopathy, the echocardiogram can allow visualization of the heart muscle and the chambers of the heart. It can be used to evaluate the ability of the canine heart to pump effectively. In dogs with dilated cardiomyopathy, the heart does not pump as effectively as it should. However, in the early stages of dilated cardiomyopathy, the findings may be subtle and difficult to impossible to detect.

Diagnosing Canine Heart Failure Resulting from Dilated Cardiomyopathy

Diagnostic testing for a dog that is actually sick from heart disease is a bit different than the screening procedures recommended for healthy dogs that are showing no signs of illness.

If your dog is ill, the first thing your veterinarian will want to do is a thorough examination. The examination may show evidence of a heart murmur, an arrhythmia or other signs of heart failure.

Radiographs (x-rays) of the chest are an important part of diagnosing dilated cardiomyopathy as well. Radiographs may show enlargment of the chambers of the heart and/or evidence of fluid building up within the lungs.

An electrocardiogram (EKG, ECG) may be recommended to look for an abnormal heart rate or rhythm (arrhythmia). The electrocardiogram may be a 20-30 second recording of the electrical activity of your dog's heart done in the veterinarian's office or it may be in the form of a Holter monitor.

An echocardiogram is usually recommended as part of the testing for dilated cardiomyopathy as well. For dogs that are suffering heart failure resulting from dilated cardiomyopathy, the echocardiogram is quite accurate in diagnosing the disease and is often considered the most important diagnostic test.

Your veterinarian may also recommend blood testing to rule out other causes of heart problems. Blood testing may include measurement of blood electrolytes, measurement of taurine, heartworm testing and other tests to look at your dog's overall health.

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