Mitral Valve Disease in Dogs

What is mitral valve disease in dogs? 

Mitral valve disease is when the mitral valve in the dog's heart undergoes a degenerative change where it becomes thicker and floppy. While the cause of mitral valve disease is currently unknown it’s believed that it can be inherited through a dog's genetics. 

Mitral valve disease is also referred to as mitral valve insufficiency (MVI) or mitral regurgitation and is usually associated with heart murmurs. 

The disease can also be caused by a ruptured chordae tendineae where the fibrous cords that hold the valve leaflets in position, break. This causes the valve to not close properly. 

The mitral valve is positioned between the left atrium and left ventricle and is there to prevent blood flowing back into the heart. 

What are the stages of mitral valve disease in dogs?

There are four stages of mitral valve heart disease in dogs:

• A - This is where a dog is prone to MVD but doesn’t currently show any signs of having it
• B1 mitral valve disease in dogs - This stage is where a dog has a heart murmur but no symptoms of a heart problem and no changes appear on ultrasounds or x-rays.
• B2 mitral valve disease in dogs - This is where visible changes to the shape of their heart can be seen when using an ultrasound or x-ray.
• C - This is where a dog has symptoms of heart disease such as coughing, breathing problems, walking slowly and collapsing.

What are the consequences of mitral valve disease in dogs?

A leaking mitral valve is usually spotted when heart murmurs are found. They’re caused by a turbulent flow of blood going backward through the leaking mitral valve and into the left atrium. This can occur in dogs as early as 4 years old.

At the beginning MVD tends to be asymptomatic, meaning there are no obvious clinical signs of it happening. As the condition progresses the regurgitation can become more severe as blood flows back into the atrium causing the heart's efficiency to reduce. 

Congestive heart failure will begin to develop and it can be between a couple of months or years until the heart fails.

While heart murmurs don’t mean that heart failure is imminent it does mean that congestive heart failure can occur over time.

Mitral valve disease symptoms in dogs

Typical symptoms of mitral valve heart disease include:

• Heart murmurs.
• Coughing - This is often worse at night or happens when a dog lies down or sleeps.
• Low energy and becoming slower on walks.
• Quicker breathing than usual.
• Loss of weight.
• Collapsing or fainting. 

How to treat mitral valve disease in dogs

Unfortunately replacing the mitral valve is highly difficult in dogs and isn’t usually done, however there are drugs and treatments that can be prescribed to help improve heart function:

• Diuretics - These are used to remove excess fluid from the body and stimulate the kidneys. Furosemide and spironolactone are the most common diuretics used by vets.
• Inotropes - This form of drug lowers the pressure in the arteries and veins while improving the strength of the heart. Pimobendan is now being used more during the early stages of mitral valve disease as well as during the advanced stages of heart failure, as it could help to slow down the progression of the disease or failure. However, more research is being conducted in this area to determine whether it does contribute to slowing the progression.
• Angiotensin converting enzyme (ACE) inhibitors - These lower a dog's blood pressure and reduce the resistance or afterload to blood flowing out of the heart. Enalapril and benazepril are the most common ACE-inhibitors used in dogs.
• Cardiac glycosides - This is often used for rhythm disturbances like atrial fibrillation. However digoxin (the most common drug used in veterinary medicine) can have a number of potentially harmful side effects and must be regularly monitored and regulated. 
• A low salt diet - Lowering a dogs salt intake may help to prevent retention of excessive fluid in the body and there are several low salt diets a vet may prescribe.

FAQs

What causes mitral valve disease in dogs?

The cause of mitral valve disease isn’t currently known, but it’s suspected to be inherited through a dog's genetics. 

What is end-stage mitral valve disease in dogs?

End-stage mitral valve disease occurs when there’s no response to standard medications and their typical dosage. 

Is mitral valve disease in dogs painful?

Mitral valve disease doesn’t usually cause pain, but other symptoms, like coughing and rapid breathing may cause discomfort and become a medical emergency. 

What is myxomatous mitral valve disease in dogs?

This is the most common heart disease in dogs that occurs naturally. This is where the mitral valve progression is degenerative and causes blood to leak backward everytime the heart beats. 

What is degenerative mitral valve disease in dogs?

This is where the valve has thickened causing blood to be unable to flow in the right direction, causing the heart to enlarge. 

What is mitral valve disease in dogs' life expectancy?

The life expectancy of a dog with mitral valve disease will vary depending on how progressive their condition is. Some dogs may live for years if the condition is detected early on and others may only have a couple of months. 

Is mitral valve disease common in dogs?

Roughly 10% of dogs will develop a form of heart disease in their lifetime and 80% of heart disease is caused by mitral valve insufficiency. The disease is more likely to occur in small and male dogs. The dog breeds more likely to develop mitral valve disease include:

• Cavalier King Charles Spaniels.
• Fox Terriers.
• Cocker spaniels. 
• Pomeranians.
• Miniature Schnauzers.
• Miniature Poodles.
• Toy Poodles.
• Chihuahuas.
• Pekingese.
• Yorkies.
• Dachshunds.

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