Cardiomegaly in Dogs
Cardiomegaly causes the heart of a dog to become enlarged. Cardiomegaly is not a specific disease, but can be caused by a number of health problems including hypertension (high blood pressure), heartworms and valve disorders. There are two main types of the condition, cardiomegaly caused by dilation, an underlying condition that causes the heart to grow, and cardiomegaly caused by ventricular hypertrophy, in which the heart grows as the result of increased pumping. Both varieties can cause serious health problems in dogs, and can result in heart failure.
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Symptoms
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Symptoms of cardiomegaly in dogs can include fatigue, shortness of breath after exercise and dizziness. Irregular heart beats or murmurs also often accompany cardiomegaly. In the long term, fluid can develop in the lungs of the dog and cause harm to the respiratory system, resulting in coughing and wheezing.
Diagnosis
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Cardiomegaly in dogs can be identified via chest X-rays and ultrasounds or electrocardiograms (ECGs). ECGs record and interpret the electrical impulses in the heart, providing veterinarians with information on heart function. According to veterinarian Rachel Peeples, while earlier stages of cardiomegaly can go undetected, in later stages of the condition the ECG will display an irregular wave pattern.
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Types
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There are two distinct types of cardiomegaly in dogs, one caused by dilation, the other ventricular hypertrophy. In cardiomegaly caused by dilation, the heart muscle itself causes the abnormal enlargement of the heart and is unable to pump out all the blood that flows in. In cardiomegaly caused by ventricular hypertrophy, the heart grows as a result of added stresses being put on it, often caused by damaged valves.
Dilated Cardiomyopathy
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One of the most common types of cardiomegaly caused by dilation is dilated cardiomyopathy. Dogs with this disease have hearts that hold more blood than can be successfully pumped out and delivered to the body. In some breeds, according to animalhealthcare.ca, dilated cardiomyopathy is the result of a deficiency in carnitine, an amino acid that boosts heart function. According to the website dvm360.com, Doberman pinschers, Great Danes, boxers, German shepherds and cocker spaniels are the most susceptible to the disease.
Mitral Valve Disease
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Mitral-valve disease is the most common occurring heart disease in dogs. Dogs suffering from this disease have valve leaflets that are mutated and unable to function properly, which results in a blood volume overload in the heart. While it was once thought that the disease was an inevitable part of the canine aging process, this may no longer be the case. According to dvm360.com, cells infected by mitral-valve disease produce serotonin, which drives the disease. If scientists can find a way to block serotonin production, they may be able to prevent or cure mitral-valve disease in dogs.
Treatment
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Treating cardiomegaly will vary depending on the underlying disease. However, diuretics--used to increase fluid output--are often prescribed alongside other drugs to decrease the swelling of the heart.
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