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What is dilated cardiomyopathy?
Dilated cardiomyopathy means that the heart muscle, becomes unable to pump properly. The pressure of the blood inside the heart then allows this weakened heart muscle to stretch, resulting in a much larger left ventricular chamber. Therefore, the two characteristics of dilated cardiomyopathy are a heart wall that does not contract or pump normally and a chamber that is much larger than normal
How common is dilated cardiomyopathy?
Dilated cardiomyopathy is not the most common cause of heart failure in dogs in general. However, this is the most common cause of heart failure in large breeds of dogs. Small breeds are only occasionally affected. The most commonly affected breeds are Boxers, Dobermans and Great Danes. Occasionally, medium sized breeds, notably Cocker Spaniels and English Springer Spaniels, and occasionally German Shepherd Dogs are also affected.
Are there any signs of heart failure which would be noticeable to me?
When the heart is not pumping properly, blood backs up into the vessels of the lungs. Increased pressure within the vessels results in small amounts of fluid leaking out of the capillaries and eventually into the air passageways. This fluid collection in the lungs produces coughing and/or gagging, the most obvious sign of heart failure. Dogs in heart failure also tire very easily from minimal exercise.
Congestive heart failure begins when the heart is not able to pump blood with adequate oxygen to the tissues. Without adequate oxygen, the body’s cells become desperate and trigger a series of responses. Various hormones are released by several organs in an attempt to correct the problem. These hormones conserve fluid in an effort to increase blood volume and the output of oxygenated blood by the heart.
For a variable period, these compensatory responses help the situation. However, increased fluid retention eventually becomes harmful. More and more fluid leaks out of capillaries, causing increased gagging and coughing, and reduced stamina. Fluid may collect in the abdominal cavity and body tissues. Fluid in the lungs is called pulmonary oedema, fluid below the skin is called peripheral or limb oedema, and fluid in the abdomen is called ascites (dropsy). Congestive heart failure is a common cause of these signs.
My dog seemed to get very ill just in the last day or two. How can this happen?
Dilated cardiomyopathy may have a very sudden onset. Some dogs go into severe heart failure in what appears to be a matter of hours. Rapid, heavy breathing, a blue tongue, excessive drooling, or collapse may be the first signs.
What tests are done to assess the situation?
There are several tests that are used. All provide valuable information while looking at different aspects of heart function.
Listening with a stethoscope (auscultation).
This valuable tool allows us to identify murmurs, their location, and their intensity and an abnormal heart rhythm (arrhythmia or dysrhythmia). It also allows us to hear lung sounds; this aids in our understanding of what is happening within the lungs. Thus the lungs are also affected.
Chest radiographs (x-rays).
These give us the best look at the lungs and a view of the size and shape of the heart. In most cases, dilated cardiomyopathy causes tremendous enlargement of the heart. These changes are usually very apparent on the x-rays.
Ultrasound examination (Echocardiogram, ultrasonography).
This examination uses sound waves which bounce off the structures of the heart and are read on a TV-like monitor. It gives the most accurate determination of the size of each heart chamber, and permits measurement of the thickness of the heart walls. This is seen on the monitor in actual time so the contractions of the heart can be evaluated. Certain measurements can be taken which allow the actual strength of the heart’s contraction to be measured as a number and compared to the normal animal. Ultrasound may not be available in all Veterinary practices because of the additional training needed to learn how to perform the examination and because of the cost of the sophisticated equipment.
. This is an assessment of the electrical activity of the heart. It allows us to accurately determine heart rate and to more accurately identify any abnormalities of rhythm that may be present.
The combination of all of these tests gives us our best evaluation of the dog and its heart function. However, if cost considerations prohibit us performing all of them, two or three will provide much valuable information.
Is there a treatment for heart failure caused by dilated cardiomyopathy?
If the dog has a sudden onset of heart failure, rapid administration of the proper drugs is essential to survival. Treatments must be precisely tailored to the individual dog
How much longer will my dog live?
There are many factors that must be considered before this question can be answered. The results of the tests are important, and the response that occurs within the first few days is another indicator.
If response does not occur within a few hours to days, the prognosis is not good. However, most dogs that stabilise quickly will live for a period of a few months to many months, but the long-term prognosis is not good. It can be difficult to generate an accurate estimate for life-expectancy when a dog has heart disease because many variables impact on survival, not least of which is the dog’s activity levels.
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