Endocarditis is an infection of the inner lining of the heart and heart valves. It is caused by the entry of infection or bacteria into the bloodstream, so can occur secondary to infections of the uterus (pyometra) or prostate, bite wounds and abscesses, or even in periodontal disease. The mitral and aortic valves are the most common sites of vegetation growth in dogs. These vegetations progressively damage the valve leaflets, resulting in irreversible destruction and often very severe regurgitation (where the blood leaks back through the damaged valve). Parts of the vegetation, clot and even infected tissue itself can also break off (embolise), causing stroke, or occluding blood flow to other parts of the body.
In humans, endocarditis is most common in patients with foreign bodies inside their hearts (for example, catheters and picc lines in patients on dialysis, or some types of implanted defibrillators or pacemakers), after invasive dental work or surgery, or in intravenous drug users. Endocarditis is also more likely to occur in patients who have artificial valves, or their own valve is congenitally abnormal or degenerative, as the haemodynamic conditions of these types of valves provides a surface to which vegetations can potentially adhere.
In both humans and animals, endocarditis usually presents as fever, lethargy, and shortness of breath. A murmur is often detected by the doctor or veterinarian. Positive blood cultures support the diagnosis, as does the identification of a vegetation on ultrasound. Transesophageal echocardiography is generally the most sensitive test, but is rarely available in the veterinary setting, and often unsuitable even with human patients. Therefore, transthoracic echocardiography is the first line diagnostic test to search for evidence of endocarditis, either by spotting a vegetation or from secondary clues, such as significant, acute valve regurgitation that is often quite eccentric in its direction.
Endocarditis can progress very rapidly, and if left untreated, is almost always fatal.
Below is a video of two scans performed 6 days apart in a patient with aortic valve endocarditis.
You can see just how quickly this condition progressed (despite strong antibiotics) from a single vegetation attached to the aortic valve with moderate regurgitation, to severe, almost free-flow regurgitation, and abscess formation in the right coronary sinus.