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Heart Inflammation (Myocarditis) in Dogs

Myocarditis in Dogs

Myocarditis in canines refers to the inflammation of the heart’s muscular wall, known as the myocardium. This inflammation is typically triggered by various infectious agents such as bacteria, viruses, rickettsiae, fungi, and protozoa. These agents can directly affect the heart or reach it from other parts of the body, leading to myocarditis.

The clinical symptoms exhibited by affected dogs vary depending on the type of infection and the severity of the lesions. In severe cases, myocarditis can result in heart failure.

Symptoms and Types

Myocarditis can manifest as either focal or diffuse inflammation within the myocardium. Additional symptoms linked with myocarditis encompass:

  • Arrhythmias (abnormal heart rhythm)
  • Cough
  • Exercise intolerance
  • Difficulty breathing
  • Weakness
  • Collapse
  • Fever

Furthermore, other symptoms associated with infections might also be evident.


While viral, bacterial, rickettsial, fungal, and protozoal infections are typically the primary causes of myocarditis, drug toxicity affecting the heart can also contribute to its occurrence.


To diagnose myocarditis in your dog, it’s essential to provide a detailed history of your pet’s health, including when symptoms began and their nature. The veterinarian will then conduct a comprehensive physical examination, focusing on the cardiovascular system. Various laboratory tests, including a complete blood count (CBC), blood culture, biochemistry profile, and urinalysis, will be utilized to identify the causative organism. The abnormalities detected in these tests will vary depending on the affected organ.

Additionally, an echocardiogram (EKG) will be performed to assess the extent of myocardial damage and any abnormal accumulation of fluid around the heart. EKG findings not only help in assessing heart dysfunction but also aid in determining the location of lesions within the heart. Thoracic X-rays will also be conducted to evaluate heart size, the presence of fluid in the lungs, and other abnormalities.

Further specific testing may involve pathological examinations of fluid samples taken from around the heart.


Dogs diagnosed with severe myocarditis, congestive heart failure (CHF), or significant heart rhythm disturbances may require hospitalization for intensive care and treatment. If a specific causative organism is identified, appropriate medications will be administered to address the infection, such as antibiotics for bacterial infections. Additionally, medications aimed at correcting heart rhythm abnormalities will be prescribed if necessary. In certain cases, implanting a pacemaker may be deemed necessary for patient management.

Living and Management

The overall prognosis for myocarditis depends on the severity and extent of the disease. Dogs with congestive heart failure (CHF) resulting from myocarditis typically have a poor prognosis, whereas those with milder forms of the condition tend to respond well to treatment.

Regular visits to your veterinarian for follow-up evaluations are essential, along with frequent laboratory testing to monitor progress and response to treatment. It’s important to limit your dog’s activity during recovery and provide a quiet resting place away from household activity, children, and other pets.

Your veterinarian may recommend certain dietary restrictions, particularly regarding your dog’s salt intake, to support their recovery process.

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