Heart Inflammation (Myocarditis) in Cats

By PetMD Editorial on Feb. 14, 2010

Myocarditis in Cats


Inflammation of the heart's muscular wall (or myocardium) is medically referred to as myocarditis. It is often caused by bacterial, viral, rikettsial, funal, and protozoal infections, which may affect the heart directly or reach the heart from other body parts.


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




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.




You will need to give a thorough history of your cat’s health, including the onset and nature of the symptoms. The veterinarian will then conduct a complete physical examination, paying close attention to the cat'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 cat 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.



Cats with severe myocarditis, congestive heart failure (CHF), or severe heart rhythm problems may need to be hospitalized for intensive care and treatment. If specific causative organism is identified, infection will be treated with suitable medicine, such as antibiotics to fight off bacterial infections. There are also medications to correct heart rhythym issues, should the cat be suffering from them. In some patients, a pacemaker may need to be implanted.


Living and Management


The overall prognosis for myocarditis depends on the extent and severity of disease. Cats with CHF as a result of myocarditis, for example, have very poor prognosis, while those with milder forms of the disease respond well to treatment.


You will need to visit your veterinarian regularly for follow-up evaluation and frequent laboratory testing will be conducted to monitor progress and response to treatment. Limiting your cat's activity is important for recovery, as well as setting aside a quiet place for it to rest, away from household activity, children, and other pets.


Certain diet restrictions may be recommended, especially those concerning your cat's salt intake.

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