Endocarditis is caused by a bacterial infection and can only be confirmed by positive blood cultures; however, it is sometimes possible to see the vegetations on echocardiography, or at the very least, the regurgitation that so often results from this infection.
Patients usually present with lethargy and a fever, but can also present with lameness or neurological signs (Berrezaie et al., 2022). You may also hear a new murmur because of this patient’s new regurgitation.
The typical appearance of endocarditis on echocardiography is a mobile mass, usually attached to the surface of a valve leaflet. They are often described as having an “oscillating” appearance, because they don’t move entirely with the valve, and instead can look like they are “blowing in the wind.” In both dogs and cats, the mitral and aortic valves are the most commonly affected.
In the video below, look at the movement of the vegetation on this patient’s mitral valve.
Endocarditis cannot be excluded with echocardiography. This means that just because you do not spot a vegetation on ultrasound, that does not mean you can exclude endocarditis in your patient. This is really important.
To increase your chances of spotting endocarditis on echocardiography:
- Use the highest frequency possible, to maximise resolution
- Optimise depth and/or zoom, particularly over the valves
- Examine the valves from multiple angles and views
Get creative with your views
You may sometimes need to go off-axis or take unusual cuts through the valves in order to be sure you’ve examined every part. Remember, a valve is a 3D structure, and with echocardiography we are looking at one 2D slice at a time. If there is only one vegetation or the vegetations are small and localised to one part of a valve, you will actually miss it if your imaging is perfect and you are cutting dead through the centre of the valve.
Above: Diagram of the mitral valve in short axis. The pink is the anterior (or septal) leaflet, and the blue is the posterior (or mural) leaflet. You can see that, by achieving a perfectly on-axis cut in the right parasternal long axis view (through A2/P2), you would actually miss the vegetations on this valve.
What is unlikely to be endocarditis?
I have, many times, seen normal papillary muscles confused for vegetations, usually from a foreshortened apical view where one of the papillary muscles is coming in and out of plane throughout the cardiac cycle. To those new to echo, it can understandably appear to them that “a mass” is flicking in and out of view, which they suspect to be endocarditis. Usually, this is after hearing a murmur, but in the absence of any clinical signs of positive blood cultures – making it unlikely that what they are seeing is a mass.
Ruptured chordae can also be confused with endocarditis. They can display many of the typical signs: an oscillatory appearance, and torrential mitral regurgitation that is often acute in presentation. Endocarditis can cause ruptured chordae but a ruptured chord is not always due to endocarditis! Again, it is important not to rely on echocardiography alone for any diagnosis of endocarditis.
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Berrezaie, M. et al. (2022). Infective endocarditis in dogs in the UK: 77 cases. Journal of Small Animal Practice.