Heart Disease (Mitral Valve Disease)

Heart Mitral Valve Disease (MVD), or more correctly, myxomatous mitral valve disease (MMVD) is the leading cause of death of Cavalier King Charles Spaniels throughout the world. MVD is a complex polygenetic disease which afflicts half of Cavaliers by the age of five and nearly all Cavaliers by age ten years, should they survive that long.

What is it?
Diagnosis
Symptoms
Treatment
Research
MVD Breeding Protocol

What is it?

MVD is a degeneration of the heart's mitral valve, one of four sets of valves in a dog's heart. As the mitral valve degenerates, the valve no longer fully closes after each pumping action, allowing some blood to flow backwards through it from the ventricle back into the atrium. As the condition worsens, more and more blood is able to backflow through the valve. In the final stages, the valve's struts sometimes break, causing the valve to collapse completely. MVD results in congestive heart failure in the CKCS.

Mitral valve disease is the most common heart disorder in older dogs of all breeds, affecting more than one third of dogs over 10 years of age. However, in the Cavalier, the prevalence of MVD is about 20 times that in other breeds, possibly reaching a life-threatening stage within as little as 1 to 3 years.

Diagnosis

All Cavaliers should be screened for heart murmurs once a year from the age of one year. Once MVD is detected, its progression can be monitored with a stethoscope (auscultations), x-rays, and echocardiograms. If a heart murmur is detected, it should be confirmed in 3 to 6 months.

Mitral valve murmurs are graded from the mildest and least audible, Grade 1, to the loudest and most turbulent, Grade 6. Most Cavaliers show a gradual progression in the loudness of the MVD murmur. The loudness of the murmur usually indicates the severity of the valve leak.

The progression of mitral valve disease can be rapid or slow. In most Cavaliers, the disease shows a gradual progression in the loudness of the murmur and to more serious symptoms.

Symptoms

Grades 1 and 2 murmurs are usually subclinical but as MVD progresses the early symptoms shown are exercise intolerance, breathlessness, coughing, a distended abdomen, weight loss and fainting. Breathlessness is the most common sign, starting as excessive panting with exercise.

Severe mitral valve disease can mean that a dog will have difficulty breathing even while at rest and will not tolerate even minimal exercise. A dog with end stage MVD suffers from a progressive deterioration of its quality of life, due to an inability to keep him free from fluid congestion, together with enlarged heart chambers, lethargy, collapse, and deterioration of its kidney and liver functions. At this stage no drug is able to remove enough of the fluids and increase the supplies of blood and oxygen to the heart, resulting in heart failure.

Treatment

Canine mitral valve disease cannot be cured but treatment with drugs can alleviate symptoms and prolong good quality of life. Dogs with MVD should not be allowed to become overweight as this puts extra strain on the heart and extreme exertion should be avoided.

Moderate MVD involves fluid and salt retention and such dogs are commonly treated with diuretics such as Frusemide. Dogs with severe mitral valve disease are now treated with pimobendan (Vetmedin). This relatively new drug (2007) has been shown to improve the quality of life for dogs suffering from chronic heart failure due to MVD.

For a more detailed explanation of all aspects of mitral valve disease visit Rod Russell's awesome website on Cavalier health.

Also visit the UK Cavalier Club's website.

Dr Brendan Corcoran's recently published paper, 'Understanding Mitral Valve Disease' (March 2009) is recommended and is published on the Cavalier Club website.

Research

Information on the various research projects worldwide may be found here.

And, 'Exciting New Developments in Mitral Valve Research' (Lupa Project), Simon Swift (2008). This European project aims to find the genes responsible for MVD.

It is planned to include MVD in the Estimated Breeding Values (EBVs) program at the Animal Health Trust. A full explanation of the EBV program can be found here.

MVD Breeding Protocol

The Breeding Protocol aimed at breeding away from early onset MVD can be downloaded here.

Sadly, in 15 years of this protocol being in place the incidence of early onset MVD has not improved. It is still the case that 50% of Cavaliers have a heart murmur by the age of five, and still far too many Cavaliers suffer and die young because of it. This is because the voluntary code of practice is ignored by the majority of Cavalier breeders, who routinely breed their dogs under the age of two and a half years.