Mitral Insufficiency in Dogs

15 January, 2020
Mitral insufficiency is when the mitral valve doesn't or can't function properly. In this article, we'll tell you all about the condition and the key things you need to know.

Mitral insufficiency in dogs is associated with different disorders that lead to degeneration or deformation of the mitral valve. Experts also call it mitral regurgitation (MR) or mitral incompetence. Today, we’ll explain the function of the mitral valve and the complications that can come about as a result of its degeneration.

The structure of the heart

The heart is divided into two sides – right and left – and each side has two chambers. The two upper chambers are the atria and the two lower chambers are the ventricles.

Blood enters the heart from the body via the right atrium and passes to the right ventricle. It’s then sent to the lungs to release carbon dioxide and absorb oxygen.

Blood flow and valves

The oxygenated blood then returns to the heart, enters the left atrium and then flows to the left ventricle. At this point, it’s pumped through the aortic artery to deliver oxygen to the whole body.

The heart valves are located between the ventricles and the atria, and their job is to control the flow of blood through the different chambers of the heart. This helps to regulate the heart rate and blood flow.

A happy dog lying on some pebbles.
Source: Travel and Roll

The mitral valve is on the left side of the heart and separates the left ventricle from the left atrium. Its main job is to stop oxygenated blood returning to the atrium so that it can be pumped from the ventricle.

On the right side is the tricuspid valve, where the blood enters. This valve helps to keep blood flowing to the lungs and stops it from stagnating in the atrium.

What is mitral insufficiency in dogs?

Insufficiency is when a structure or organ in the body fails to perform its role correctly or fully due to an anomaly. This can be the result of either internal or external factors.

With the mitral valve, insufficiency happens when the valve doesn’t close properly. This stops blood from being pumped to the body and instead it returns to the left atrium.

To try and keep things in order, the body performs certain maneuvers to keep tissues and organs oxygenated. However, as the situation gets worse, these mechanisms eventually aren’t enough.

Causes of mitral insufficiency in dogs

We don’t yet know the exact cause of mitral valve deformation. Many specialists argue that it’s caused by a systemic change in collagen production and that it may even be partly hereditary.

However, we know that aging is a natural cause that can lead to a weakening of the structures in the heart. Pregnant females are also at risk.

Relevant causes and factors

Mitral insufficiency is also associated with the following conditions:

  • Mitral valve prolapse
  • Damage to the tendons that connect the mitral valve with the heart
  • Heart murmurs and changes in heart rhythm
  • Infection of the heart valves (endocarditis)
  • Radiotherapy
  • Trauma
  • Rheumatic fever
  • Deformations in the heart muscle (cardiomyopathy)
  • Congenital changes
  • Prolonged use of ergotamine-based drugs

Symptoms of mitral insufficiency in dogs

The clearest symptom is normally the build-up of fluid in the different parts of the body which produces swelling. Often, the animal will appear to have a large belly due to swelling around the abdomen.

Here is a list of common symptoms of cardiac insufficiency in dogs:

  • Tiredness, lack of interest and weakness
  • Cough and shortness of breath
  • Changes in heart rhythm
  • Difficulty performing physical exercise
  • Gray or blue gums, mucous membranes, or tongue
  • Fainting (or syncopes)
  • Collapsing

If the insufficiency also affects the tricuspid valve, the dog may also have problems with their liver and spleen.

A dog lying on a pebble beach with their owner.

Treating of mitral insufficiency in dogs

If you notice any of the above symptoms, it’s vital that you go straight to the vet. They will then diagnose the cardiac anomaly and identify the correct treatment.

If your dog’s health allows it, the vet may propose surgery to correct the problem. Otherwise, there are also medications available to strengthen the heart muscles.

If there is no build-up of fluid in the lungs or abdomen, the vet should take controlled samples. Diuretic drugs can also be supplied to help the body get rid of the fluid naturally and aid the proper working of the valves.

In the most serious cases, your dog may need to spend time in hospital and receive emergency oxygen therapies. Make sure it doesn’t get to that!