Heart valve disease a common cause of heart murmurs in middle aged and older small breed dogs. A heart murmurs is a change in the sound heard through a stethoscope from the normal “lub-dub” to a swooshing noise.
There are four valves in the heart and their function is to ensure that blood flows in one direction. Degeneration of the valve structure means that the valve no longer close properly and blood leaking back through the valve is the cause of the audible murmur. The valves commonly affected by degenerative change are the mitral and tricuspid valves which are located on the left and right sides of the heart respectively.
Our approach to dogs with a new heart murmur is firstly to ask some questions to find out if the murmur is causing any symptoms. Then we perform a physical examination looking at parameters such as gum colour, heart rate and rhythm, pulse quality and for any signs of fluid retention. We will then perform echocardiography – an ultrasound scan of the heart. Echocardiography is painless, does not require any sedation and you can stay with your dog throughout the scan whilst a nurse holds them on their side on a padded bed. The scan takes less than 30 minutes and most dogs tolerate it well.
Echocardiography allows us to establish the cause of the heart murmur and also obtain measurements of heart size which allow us to know whether we are dealing with mild disease or a more advanced problem.
This video is from a dog with mild valve leakage. The mitral valve is positioned vertically in the centre of the image with the left atrium on the right side of the image and the left ventricle on the left of the image:
We then superimpose colour on the image to show the direction of blood flow – red and blue show normal flow up the image from the left atrium to the left ventricle. The green flash in the atrium is due to mitral valve leakage:
These are similar images from another dog with more advanced disease result in more marked thickening of the mitral valve:
And with superimposed colour showing more severe mitral valve leakage:
If we find that your dog has degenerative valve disease then we can advise on best treatment options to keep your dog performing normal activities with minimal symptoms.