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Myocarditis in Dogs

Myocarditis is the inflammation of the heart's muscular wall (or myocardium), often caused by infectious agents. That is, bacterial, viral, rikettsial, fungal, and protozoal agents directly affecting the heart or reaching the heart from other body parts can lead to myocarditis.

Clinical symptoms depend on the type of infection and extent of lesions, but in severe cases, heart failure may result.

Symptoms and Types

The inflammation itself may be focal or diffused throughout the myocardium. Other symptoms associated with myocarditis include:

• Arrhythmias (abnormal heart rhythm)
• Cough
• Exercise intolerance
• Difficult breathing
• Weakness
• Collapse
• Fever
• Other symptoms related to infections may also be present

Causes

Although viral, bacterial, rikettsial, funal, and protozoal infections are the most common cause of myocaditis, drug toxicity to the heart can also be a factor.

Diagnosis

You will need to give a thorough history of your dog’s health, including the onset and nature of the symptoms. The veterinarian will then conduct a complete physical examination, paying close attention to the dog's cardiovascular system. Various laboratory tests -- such as complete blood count (CBC), blood culture biochemistry profile, and urinalysis -- will be used to isolate and identify the causative organism. The abnormalities revealed by these tests, however, will depend on the affected organ.

Your veterinarian will also perform an echocardiogram (EKG) on the dog to evaluate the extent of myocardial damage and abnormal accumulation of fluid around the heart. In addition to evaluating the abnormalities related to heart dysfunction, EKG findings help in differentiating the location of the lesions within heart. Thoracic X-rays, meanwhile, help evaluate the heart size, whether fluids are located in the lungs, and other such abnormalities.

Other more specific testing include pathological exams of fluid samples taken from around the heart.