Bacterial myocarditis

Bacterial myocarditis is an inflammation of the inner layer (membrane) of the heart, which is localized mainly on the endothelium of the valve leaflets and is characterized by the formation of specific growths on the leaflets - vegetations.

This disease is extremely rare in dogs. In cats, it is even less common - 0.006-0.018% of cases.

In order for the endocardial surface to be colonized and vegetations to appear, a prerequisite is persistent bacteremia. Therefore, if endocarditis is suspected, a systemic cause should be sought: abscesses, bitten wounds, catheter-induced infection, periodontitis, sepsis, etc.

Vegetations are accumulations of fibrin, microorganisms, platelets, immune cells, and inflammatory mediators.  Most often, lesions occur on the mitral valve and aortic valve.

Confirming the diagnosis is not easy. A comprehensive approach is required: history taking, thorough clinical examination of the patient, ECHO, blood tests. X-ray, ECG, blood culture are additional methods of investigation. However, the changes that can be detected by these tests are not specific, and even a negative culture result does not exclude infective endocarditis (in about 30% of cases, the culture is negative).

Duke's criteria are used to make the diagnosis. There are large and small criteria.

Large criteria:

Positive blood culture (isolation of the pathogen from 2 or more blood samples)
Signs of endocardial damage (vegetation on the valve, sudden onset of regurgitation).

Small criteria:

Fever
Thromboembolism
septic infarctions
immunological manifestations (glomerulonephritis)
repeated non-sterile intravenous injections

To make a diagnosis, it is necessary to identify two major criteria, or one major and three minor criteria, or five minor criteria.

Treatment is aggressive antibiotic therapy and supportive care.

The prognosis is usually cautious, closer to unfavorable. The mortality rate is 56%. Cats, unfortunately, are more severely affected. The cause of death in bacterial endocarditis can be heart failure, thromboembolism, renal failure, or rhythm disturbances.