Dilated Cardiomyopathy (DCM) is a disease of the heart muscle in which it becomes weak and is no longer able to contract properly. As a result, the heart becomes dilated – hence the name dilated cardiomyopathy. It requires veterinary cardiology treatment.
What causes DCM?
There are several reasons why the heart muscle may become weak, such as infectious disease and low thyroid hormone levels among others. If the heart is forced to work harder for a long time due to another cardiac disease or faster (arrhythmias), the heart muscle may also become weak and lead to dilation. All of these conditions look like DCM and have to be excluded before a definite diagnosis of DCM may be issued.
Complete understanding of the cause or causes of DCM is still not within our grasp. A genetic cause has been identified or is strongly suspected for a few breeds.
Affected breeds
- DCM is more common in large breed dogs with a few exceptions such as Cocker Spaniels and Dalmatians.
- Doberman
- Great Dane
- Irish Wolfhound
- Newfoundland
- Portuguese Water Dogs
Onset and natural progression
DCM is an adult onset disease – often around 5-7 years – except in the Portuguese Water Dog. Most of the information available refers to the Doberman breed and the disease may be roughly divided into 3 stages:
Stage 1 – Dogs with the disease but without any signs of heart disease
Stage 2 (Occult Disease) – Evidence of disease (heart dilation and/or irregular heartbeats) but no clinical signs (lasts 2-4 years)
Stage 3 (Overt Disease) – Clinical signs of heart failure
Diagnosis
Overt stage
Heart muscle “weakness” and enlargement of the heart may be easily identified on an ultrasound scan of the heart – echocardiographic examination. Other diseases are also excluded with this exam. A 24 – 48 hour electrocardiogram – Holter examination – allows proper assessment of the heart rate and rhythm to diagnose and manage the arrhythmias which are common in this disease. Chest radiographs allow identification of signs of congestive heart failure, such as fluid in the lungs or chest cavity. Blood pressure measurement and blood tests to assess kidney function and electrolytes complete the necessary information to appropriately manage this disease.
Occult stage
Diagnosis of DCM in the occult stage constitutes a challenge. Yearly examinations with echocardiography and Holter monitoring are advised in predisposed breeds in order to identify affected dogs at a very early stage.
“Any signs of arrhythmia, heart murmur or heart enlargement should prompt a cardiovascular examination in any dog”
Unfortunately, identification of affected dogs that are still normal but go on to develop the disease later in life is still not possible.
Treatment
Unfortunately a cure does not exist for this condition. A combination of drugs is used to control signs of congestive heart failure and prolong life with the best quality of life possible.
Overt stage
- Furosemide is used to excrete the excess fluids in the body and treat congestive heart failure
- ACE inhibitor is used to counteract fluid retention by the kidneys and dilate the blood vessels and lessen the load on the heart
- Pimobendan is used to improve heart muscle strength and dilate the blood vessels to lessen the load on the heart
- Anti-arrhythmic drugs are also given if necessary
Occult stage
Significant arrhythmias may warrant therapy with anti-arrhythmic drugs.
Treatment with Pimobendan is recommended as it contributes to a delay in the onset of heart failure and improves survival time.
Monitoring
Overt stage
Regular examinations will be necessary to appropriately manage DCM at this stage.
What will happen during a re-examination?
At each visit you will be asked a number of questions to assess how your dog is coping with treatment and with the condition. After being examined, blood pressure will be measured and an echocardiographic examination and thoracic radiographs will normally be repeated. Some blood tests will be essential to assess how the kidneys are coping with treatment and disease, and also provide further important information needed for treatment adjustments. Regular Holter examinations will probably also be necessary.
Monitoring at home
An easy and reliable way to monitor for signs of heart failure (fluid in the lungs or chest) is to monitor the breathing rate at home during sleep. Count the number of breaths in 15 seconds and multiply by 4. Values above 30 suggest the presence of heart failure.
Treatment adjustments
After any treatment adjustments a brief re-check at your vet may be necessary. The same blood tests will be repeated to assess the kidneys response to therapy, blood pressure and eventually chest x-rays if there has been previous congestive heart failure. Usually this is performed 5-10 days after the initial examination.
Occult stage
Yearly examinations with an echocardiographic examination and Holter examination.
Prognosis
Overt stage
Depending on response to therapy, some dogs may cope well with the disease for a fair amount of time, whereas others unfortunately do not. This varies with each case and is very difficult to predict. Sudden death is possible, especially in the Doberman.
Occult stage
This stage may last for up to 4 years or more in which no external signs of disease are perceived. Some dogs will die suddenly during this stage without ever showing clinical signs up to that point. This is more common in the Doberman breed.