News // 3.5.20

Heart Awareness - Myxomatous Mitral Valve Disease

Case: Poodle cross with a heart murmur

Harry is a 10 year old, male neutered, Poodle cross who presented to Allambie Vet for a routine lump assessment and surgical removal. On examination it was found that Harry had a heart murmur, recorded as a grade 3/6 systolic murmur. The veterinarian recommended that Harry’s heart murmur be investigated to obtain a diagnosis. A diagnosis would allow us to further understand his anaesthetic risks and to start treatment if required.

Harry was scheduled for an echocardiogram with Dr Jane. The Echocardiogram identified that Harry had an abnormal, degenerative mitral valve diagnosing ‘myxomatous mitral valve disease’.

What is Myxomatous Mitral Valve Disease (MMVD)?

In myxomatous mitral valve disease (MMVD), the thickened valve stops an appropriate seal forming between the atrium and ventricle on the left side of the heart. This then causes a back flow of blood into the atrium during heart contractions resulting in increased pressure within the atrium. Over time this causes the atrium to enlarge – a term referred as cardiac remodelling or cardiomegaly. 

How to treat MMVD

The latest studies on treatment of myxomatous mitral valve disease are based on how much the left atrium has enlarged compared to the aortic valve/root (or the LA:Ao ratio). If the atrium is greater than 1.6x the size of the aorta, then treatment with a positive inotrope (pimobendan) is recommended to allow more efficient contractility of the heart. Starting pimobendan early in the course of heart disease is associated with longer survival times and a later onset of heart failure (EPIC study: Boswood et al. 2016).

In the case of Harry, his left atrium was 2.39x the size of the aortic root! Thankfully, there were no signs of heart failure at this stage. Harry was started on pimobendan twice daily and his surgical procedure postponed for two weeks. We are looking forward to reassessing Harry before his surgical procedure. 

The vets at Allambie are far more comfortable knowing exactly what is going on with Harry’s heart so that we can tailor his anaesthetic plan.

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