Mitral Valve Disease (MVD)

What is it?

The mitral valve sits between the left atrium and left ventricle. In mitral valve disease (also called myxomatous or degenerative mitral valve disease, or mitral insufficiency), the valve thickens and becomes floppy, so it no longer closes properly. About 80% of heart disease in dogs is due to this condition. It is more common in small breeds and in males; predisposed breeds include Cavalier King Charles spaniels, Chihuahuas, miniature schnauzers, poodles, Pomeranians, Yorkshire terriers, and dachshunds.

What signs should I watch for?

The first sign is usually a heart murmur your veterinarian hears, sometimes as early as four to six years of age. Many dogs have no signs for months to years. As leaking worsens, heart failure can develop: watch for gagging as if clearing the throat, a chronic hacking cough, and tiring more easily on walks. A rising sleeping or resting breathing rate can mean the condition is getting worse.

How is it diagnosed and treated?

Diagnosis uses a physical exam and stethoscope, chest X-rays, blood and urine tests, an ECG, and an echocardiogram, which is the most useful test and is repeated over time. Treatment depends on the stage (A to D) and may include pimobendan, diuretics, ACE inhibitors, other heart drugs as needed, and a lower-salt diet with no high-salt treats.

Can it be prevented, and what's the outlook?

• The cause is unknown, though genetics likely play a role in some breeds, so it cannot be prevented.
• Most dogs with heart failure need lifelong treatment, but many that stabilize quickly enjoy good quality of life for many months to a few years.
• Counting your dog's resting breathing rate at home helps your vet track how treatment is working.