Cardiomyopathy is defined as degeneration of the heart muscle. As a result of this degeneration, the muscle becomes thinner, particularly the thick muscle wall of the left ventricle. The pressure of the blood inside the heart causes these thin walls to stretch resulting in a much larger heart. This condition is described as Dilated Cardiomyopathy (DCM).
How common is the condition?
Dilated cardiomyopathy is the most common cause of heart failure in certain large breeds of dogs. These include Boxers, Dobermans, and Great Danes. Occasionally, German Shepherd Dogs and some medium sized breeds such as Cocker Spaniels, English Springer Spaniels are also affected. Small breeds rarely develop DCM.
Dilated cardiomyopathy may have a sudden onset of clinical signs, although the heart disease has been developing slowly and insidiously. Some dogs may develop severe congestive heart failure (CHF) in only a few hours. Rapid, heavy breathing, a blue tongue, excessive drooling or collapse may be the first signs.
How is the condition diagnosed?
Before a diagnosis of dilated cardiomyopathy is made, several tests are performed to assess different aspects of heart function.
Auscultation. Listening to the chest with a stethoscope allows the veterinarian to identify murmurs due to the improper closure of heart valves. The murmur’s location and intensity helps determine its significance. Heart rhythm is also assessed during auscultation, and if there are concerns, the veterinarian may simultaneously palpate or feel the pulse to determine its strength and rhythm. Auscultation is also used to evaluate the lungs.
Blood and urine tests. We are especially concerned about liver and kidney function because these organs are often impaired in heart disease.
Chest X-rays. Chest radiographs allow us to examine the lungs and measure the size and shape of the heart. Dilated cardiomyopathy usually causes obvious enlargement of the heart, particularly the left side.
Electrocardiogram (ECG). This is an assessment based on the electrical activity of the heart. It allows us to accurately determine heart rate and to diagnose any abnormal rhythms.
Ultrasound examination (echocardiogram). This gives the most accurate determination of each heart chamber’s size and thickness of the heart walls. Measurements of the heart contractions can be taken to evaluate the heart’s pumping efficiency.