What is Endocarditis In Dogs?

If a dog has heart failure, there’s a very good chance that endocarditis is to blame. As VetStreet notes, endocarditis is at the root of around two-thirds of heart disease cases in dogs, making it the number one cause of canine heart failure. Despite that, it’s still a rare condition, which, combined with the fact that no single test can confirm its occurrence, makes it difficult to diagnose. Endocarditis is caused when bacteria enters the body (sometimes via systemic infection, other times via a wound, an abscess, a surgical procedure, or even advanced dental disease) and makes its way to the heart via the bloodstream.

Although endocarditis can affect any one of the heart valves, it most typically attacks the mitral and aortic valves. As a result, blood flow through the heard is restricted to one direction only. In severe cases (known as vegetative endocarditis), visible clumps of bacteria, inflammatory cells, and clotted blood can be seen at the site of the infection. Once endocarditis develops, the infection can rapidly spread from the heart to other organs. Even so, it’s the damage done to the heart that is the most life-threatening.

Symptoms of Endocarditis

As the heart affects so many functions of the body, the symptoms of endocarditis present themselves very quickly, and in a number of different ways. In the early stages of the disease, a low-grade heart murmur may be the only symptom. As it progresses, other symptoms can come into play. While many of the symptoms are similar to those found in other illnesses, be vigilant if you notice your dog develop one or a combination of the following;

  • Coughing
  • Arrhythmia
  • High blood pressure
  • Collapse
  • Lameness
  • Joint Pain
  • Weakness
  • Fatigue
  • Weight loss and anorexia
  • Shortness of breath or breathing difficulty
  • Exercise intolerance
  • Ascites (fluid in the abdomen)
  • Fever
  • Heart murmur

Causes of Endocarditis

Typically, endocarditis is caused by a bacterial infection. The infection can develop in any part of the body, before being transported to the heart via the bloodstream. Certain things can increase the risk of a dog developing endocarditis, including cancer, surgical procedures, and immunosuppressive medical treatments. A pre-existing heart condition can also make dogs more susceptible to the disease – those with a weakened immune system are similarly at risk. Males dogs and older dogs are most vulnerable to developing the disease, and while it can occur in all dogs, larger breeds such as Labrador Retrievers, German Shepherds, German Shepherd mixes, Golden Retrievers, and Rottweilers tend to be at most risk.

Diagnosis of Endocarditis

If your dog presents the symptoms of endocarditis, your vet will carry out several physical tests to confirm a diagnosis.

  • Blood tests (including a complete blood cell count and serum biochemistry). A blood test will pick up any signs of abnormalities that may suggest either endocarditis or some other infection.
  • Chest radiographs (X-rays). A chest x-ray will be ordered to check for signs of heart failure or enlargement.
  • Electrocardiography (ECG). As endocarditis can often result in an irregular heartbeat, an ECG will be ordered to check for abnormalities.
  • Echocardiography (ultrasound of the heart). One of the most useful means of detecting endocarditis is by taking an ultrasound of the heart, which allows your vet to see the condition of the heart valves.
  • Infectious disease testing. Your vet may sometimes order blood tests to check for specific pathogens. Although blood tests can be useful in establishing the agent involved, they are not always the most reliable mean of diagnosis and can often yield false-negative results.

Unfortunately, there’s no sure-fire, definitive way of diagnosing endocarditis, and your vet will often need to complete several rounds of tests before establishing a diagnosis. If multiple tests show findings that are consistent with endocarditis, your vet will take this as sufficient to confirm the disease and to proceed with treatment.

Treatment of Endocarditis

Once a diagnosis has been confirmed, your vet will begin a course of treatment. Endocarditis is treated with a long-term course of antibiotics, which can be prescribed for anything from 3 to 6 months. As well as treating the disease itself, your vet will usually prescribe supplementary medications to support with any of its associated symptoms. As endocarditis can present itself in one or more of multiple symptoms, these medications may include pain medications, IV fluids. and medications to treat heart failure (diuretics, cardiac glycosides, vasodilators, and angiotensin-converting enzyme inhibitors).

As PetPlace notes, antiarrhythmic drugs may be prescribed to control severe or potentially life-threatening abnormal rhythms. Very occasionally, a dog may experience septic shock, a complication that can be lethal and, unfortunately, hard to reverse. Your vet may attempt one of several treatments (including administering intravenous fluids, antibiotics, and glucocorticoids (although the latter is considered controversial) to treat the condition.

Throughout the course of treatment, your vet will continue to monitor your pet to check the progression of the disease. Depending on the individual circumstances, they may order additional chest X-rays, blood tests, and heart testing. While treatment is ongoing, it’s vital to watch for signs of a continued or recurring infection. Loss of appetite, lethargy, weakness, joint pain, limping, intolerance to exercise, coughing and difficulty in breathing should all be reported to your vet as soon as possible.

Prognosis of Endocarditis

The prognosis of endocarditis can vary. Factors such as a dog’s overall health, their age, the heart valve affected by the disease, and the bacteria responsible for causing the disease can all influence the overall prognosis. If the endocarditis has affected the aortic valve, the prognosis is usually poor. Progression of endocarditis which has affected the mitral valve and has not developed into congestive heart failure, however, is much slower, and dogs are expected to live normal lives provided antibiotics are properly administered.


The most crucial aspect of treatment is to ensure that all prescribed medication is administered as directed. If you notice any adverse reactions, or if any other symptoms develop, notify your vet as soon as possible. Your vet may also recommend a diet that will help manage heart or kidney failure, depending on the particular needs of your dog.

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