Heart Valve Infection in Cats

Though the condition is rare in cats, the complications of it can lead to heart failure and death. Prompt treatment of the underlying infection is necessary in order to save the cat's heart and life.

The heart wall is composed of three separate layers: the inner endocardium, the middle myocardium and the outer epicardium. When the endocardium becomes infected, infective endocarditis results, causing infection in the inner heart wall and one or more heart valves. Any generalized infection can cause an infection in this portion of the heart.

Symptoms can differ in type and intensity depending on the site of the initial infection, the health of the heart and complications from the underlying infection. These symptoms may include:

• Weakness
• Lethargy
• Reluctance to exercise or move
• Body pains and aches
• Lameness or inability to walk that may be intermittent
• Weight loss
• Loss of appetite
• Dry cough
• Blue discoloration of mucous membranes
• Breathing difficulties
• Elevated respiratory rate
• Vomiting
• Diarrhea
• Shaking
• Abdominal pain
• Depression
• Seizures

Infective endocarditis can be caused by a variety of generalized infectious organisms. Cats who have weakened immune systems, have recently had surgery or who have a previously weakened endocardium are most susceptible to these infectious organisms. The most common infectious organisms known to cause infective endocarditis include:

• Staphylococcus aureus
• Pasteurella spp.
• Streptococcus spp.
• Pseudomonas spp.
• Corynebacterium spp.
• Escherichia coli
• Erysipelothrix rhusiopathiae
• Bartonella spp.
• Actinomyces turicensis 

The veterinarian will need to know the cat's complete health history, which will include any recent surgeries, heart problems or hospitalizations, a complete list of all of the cat's symptoms and an approximate date when the symptoms first began.

The veterinarian will perform a physical examination of the cat by taking its temperature, listening to its lungs and heart with a stethoscope, taking its blood pressure, and looking for discoloration in the mucous membranes. The veterinarian will also look for any problems with the cat's gait, which could signify a blood clot.

A complete blood count, biochemical profile and a urinalysis will be completed. These tests can help the veterinarian determine if an underlying infection is present and the infection's effect on the organs of the body. A blood culture will also be performed. The blood culture will identify the specific underlying infection, which will help determine the best antibiotic to treat the bacteria.

An X-ray may be taken in order for the veterinarian to do a visual examination of the lung cavity. An echocardiogram (ECG), which is an ultrasound of the heart, will be performed. The echocardiogram can show the veterinarian any inflammation that may be present as a result of the infection and show how the heart is functioning. As blood cultures are only positive in 50 to 90 percent of cases, the ECG is the most important diagnostic tool in heart valve infection cases. An electrocardiogram (EKG) may also be done. An EKG shows the electrical activity in the heart and can show any skipped heart beats or palpitations that are occurring.

Fluid Therapy

Cats who have been diagnosed with infective endocarditis will need to be hospitalized for treatment. Fluids will be administered intravenously to prevent dehydration and ensure that the other organs have the fluids necessary to function properly. The veterinarian will monitor the fluid's effect on the other organs, such as the kidneys and lungs, if the heart isn't pumping properly.

Antibiotic Therapy

Antibiotics will need to be given for approximately 12 weeks in order to clear the underlying infection that caused the infective endocarditis. A generalized antibiotic will be given until the blood culture has identified the infectious organism and the proper antibiotic to treat it.

When caught early, cats with a mild heart infection typically respond well to aggressive treatment and make a full recovery. If the infection has spread beyond the heart wall and into the valves, however, the prognosis is poor.

The cat will need to remain in the hospital where the veterinarian will draw blood labs regularly to determine how the infection is responding to the antibiotics. After the infection has cleared, follow up appointments will need to occur to re-test blood samples to ensure that the infection hasn't returned. If other organs were affected by the infection, treatment for any accompanying conditions will need to take place. Because infective endocarditis can permanently affect the heart's function, the veterinarian may recommend a specialized diet to help decrease the heart's workload.