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Heart disease in small dogs

You might be surprised to find out that dogs can get heart disease too, just like humans. In fact, around one in ten dogs have heart disease.1

In dogs the most common type of heart disease is called mitral valve disease, or MVD for short. MVD accounts for 75% of all heart disease in dogs, and the disease gets worse with time.1,2

Small to medium-sized dogs have a higher risk of developing MVD, especially as they reach middle-age and beyond. But early diagnosis can give your dog the best chance of a longer, happier life. Find out more below.

What is MVD?

Just like human hearts, your dog’s heart is divided into four chambers, separated by valves which open and close so that blood flows in the right direction. In a dog with MVD, the valve between the chambers on the left side of the heart, known as the mitral valve, gradually becomes thick, lumpy, distorted and leaky.

This means that when the heart beats blood can flow in the wrong direction, leaking backwards through the valve.

What is an MVD murmur?

Lub ‘shhh’ dub. There it is – the tell-tale sign of MVD, a defect of the heart causing it to work harder to pump blood around the body.

When a vet listens with a stethoscope they hear this irregular blood flow as a ‘lub shhh dub’. Rather than a normal ‘lub dub’ sound, the ‘shhh’ is the sound of blood flowing the wrong way and is known as a murmur.


Shhh! Can you hear the murmurs of MVD?


Click here to listen to a normal heart beat

Click here to listen to a murmur heart beat

If your vet isn’t checking for a heart murmur, you won’t know it’s there. That’s why regular check-ups are so important. Dogs with heart murmurs can live many years without any symptoms and can seem happy and healthy. Your vet may refer to this stage as the “asymptomatic” or “silent” phase of MVD.

Over time the mitral valve becomes even more thickened and the leak worsens, making the murmur louder and putting more pressure on the heart. The heart compensates by working harder and it gradually becomes enlarged and less efficient

Click on the video below to learn about MVD

How does MVD progress?

MVD is a progressive disease that gets worse over time.

A dog with a leaky, damaged mitral valve can live for many years without showing any symptoms apart from a heart murmur.

However, in many dogs, the leak can worsen quickly. As more blood flows the wrong way through the heart, the murmur gets louder and more pressure is put on the heart. To compensate, the heart must grow larger and pump harder.

Eventually, there comes a point when the heart cannot cope with the additional strain any longer, and fails to pump enough blood around the body. This is known as heart failure.

Finding out whether your dog has an enlarged heart is very important, as this will allow you and your vet to:

  • Monitor the progression of your dog’s disease
  • Identify when treatment should be initiated

There are two non-invasive tests that your vet may use to determine if your dog has an enlarged heart:

  • X-rays
    A chest X-ray enables a vet to assess the overall size of the heart as well as checking for any fluid build-up in the lungs. Fluid in the lungs would indicate the presence of heart failure.
  • Ultrasound
    An ultrasound of the heart allows a vet to visualise the inside of the heart, enabling them to take measurements to assess heart size.

Symptoms of heart failure

Eventually, MVD can lead to heart failure and at this stage the symptoms are much more obvious.
Signs of heart failure include:

  • Increased<br>breathing rate

    breathing rate

  • Tiredness


  • Difficulty<br>exercising


  • Difficulty<br>breathing


  • Fainting/<br>collapse


If you recognise any of these symptoms in your dog, please speak to your vet urgently.

How can you help?

The good news is that something as simple as a routine check-up by your vet can help spot the early signs of the disease before symptoms are even visible. Detecting heart disease early is vital to prolong your dog’s quality of life.

By diagnosing early and treating the disease, it’s possible to:

  • Slow the disease progression
  • Extend your dog’s symptom-free time by delaying the onset of heart failure
  • Improve your dog’s quality and length of life

At-risk dogs should have regular check-ups, at least once a year.
Is your dog due a check-up?

  1. Atkins C, Bonagura J, Ettinger S, et al. Guidelines for the diagnosis and treatment of canine chronic valvular heart disease. J Vet Intern Med 2009; 23(6):1142–1150.
  2. Boswood A et al. Effect of Pimobendan in Dogs with Preclinical Myxomatous Mitral Valve Disease and Cardiomegaly: The EPIC Study—A Randomised Clinical Trial. Journal of Veterinary Intern Medicine 2016;30:1765-1779.
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