HOW TO BREAK A HEART

Pathophysiology of Mitral Valve Disease

Starting off our webinar this week, James McMurrough BVSc CertAVP(SAM) CertAVP(VC) MRCVS shows some startling statistics. 10% of dogs presenting to Veterinarians have heart disease, and of those a staggering 75% have mitral valve disease. A truly shocking 85% of small breeds have valve lesions by 13 years old (!), and male dogs are 1.5 times as likely to suffer from mitral valve disease. The disease itself isn’t heart failure from the beginning – there’s a long period of time where outwardly the dog is doing fine. Internally, it’s a different story. One that consists of big hearts working hard and inefficiently. Breeds to keep an eye out for are CKCS (the classics), Dachshunds, Yorkshire Terriers, Chihuahuas, and Miniature and Toy Poodles.

CLEAR THE STAGE

Staging a Mitral Valve Disease patient

If there’s one thing to remember from the entire talk, it’s the stages of mitral valve disease. It’s a succinct way to assess how the animals disease has progressed and if you need to refer then the referral vet will be up to speed quickly. Staging was first mentioned in the ACVIM consensus statement, which was revised in 2019. To make it simple, have a look at the image that I’ve attached below this paragraph. I’ve also found this PDF which is a really handy guide for treatments and diagnosis of each stage of mitral valve disease.

WHAT TO WATCH FOR

Clinical Signs of Mitral Valve Disease

The very first clinical sign that can be identified is a left apical systolic mitral murmur. You can see this as early as pre-clinical stage B1.

Many veterinarians will later fall into the trap of hearing a cough and thinking of cardiac heart failure. Unfortunately, it’s not quite as simple as that. Coughing isn’t a particularly good indicator, instead we should look for the sequelae of poor heart function.

Poor heart function can manifest as exercise intolerance and tachypnoea. If you think about the heart simply pumping weakly then the rest of the clinical signs become clear – reduced pulse quality, cachexia, hypothermia due to poor peripheral perfusion. Pale mucous membranes, prolonged CRT, and of course the end-stage signs like lung crackles and ascites.

Just because a dog with mitral valve disease is coughing, it doesn’t mean it’s in heart failure.

A BIG HEART IS NOT BETTER HEART

Identifying Cardiomegaly in Mitral Valve Disease

The key to figuring out the progression of cases of mitral valve disease is identifying cardiomegaly – that is, the structural hypertrophy of the heart seen from stage B2 and onwards. You can do this through a range of strategies that are presented in the webinar. These include Vertical Heart Score, Left Atrial Bulge, Vertebral Left Atrial Size, and Echocardiography (which is the only way to diagnose mitral valve disease – otherwise the cardiomegaly can hypothetically be caused by other factors). You can find the techniques for calculating these scores in the webinar! There are also plenty of other valuable resources online, so I’ll refrain from boring you here.

There’s also a short section on using biomarkers in the investigation. What to remember about biomarkers like Quantitative proBNP and Troponin 1 is that you can’t make a diagnosis of them. They can still be useful for screening and indicating a need for an echocardiogram.

DON’T LOSE HEART

Treatment and Management of Mitral Valve Disease

Crucially, you must remember that in cases of heart disease it’s not a case of ‘treating’, it’s a case of ‘managing’. This is a lifelong progressive disease. As this disease is progressive, we’ve staged it to pinpoint where in their heart disease journey our patients are. And further, we’ve been able to advise what the ideal treatment is for each stage of mitral valve disease. This can progress from the recommendations in stages A and B1 which are mostly just monitoring of various kinds (auscultation, radiographs) to B2 (pimobendan) and further on to the ‘quad therapy’ necessary in step C. ‘Quad therapy’ is a nice little cocktail of four different drugs which helps with the symptoms, prevents remodelling, and has been shown to be really quite good at what it’s meant to do. This can get quite expensive, so James McMurrough has also offered some slides which advise how to treat stage C mitral valve disease on a budget, and how treatment can proceed in a hospital setting. 

KEEPING YOUR FINGER ON THE PULSE

Monitoring a Mitral Valve Disease Patient.

We love attentive pet owners. Monitoring at home can be really easy for good pet owners, and there are plenty of apps to help out with calculating and recording sleeping respiratory rates and sleeping heart rates. This is a great little ‘exercise’, I suppose you can call it, which helps the client have a closer awareness of their pets health. It also helps you as a clinician to monitor any progression, and it means that if things do go badly quickly, your client will hopefully notice and bring in their pet.

HAND ON HEART

Summary

In summary, stage stage stage your mitral valve disease patients! The staging is crucial to figure out what treatment will suit Fluffy the best. There are some great resources you can save or print out for your clinic, and if you’d like to check out the webinar for more in-depth education which includes recommended drug protocols and doses, as well as alternative protocols to use when hospitalised or on a budget then you can find it here. It’s free to attend for our Unlimited Members, or you can get access for £40+VAT.

In the case you have a mitral valve disease patient that you need to anaesthetise, there are some things to consider. Good thing we’ve written a blog post about that! In the case that you need to learn about CPR, we’ve also written about that before as well!

If you have anything you’d like to add, chat about, or share then you can do that on our Facebook group.

Written by Theresa Hamilton