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Mitral endocardosis

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Definition Signs Causes Diagnosis Treatment Prevention Complications When to see a vet Prognosis FAQ Sources Affected species

What is it?

Mitral endocardosis is the most common heart disease in dogs, especially in small, aging breeds. The mitral valve, which separates the two left chambers of the heart, thickens and distorts over time. It no longer closes properly: with each beat, part of the blood flows backwards instead of being sent to the body. It is this reflux that the veterinarian hears through the stethoscope in the form of a murmur. The disease progresses very slowly. Many dogs live for years with a murmur without ever showing the slightest sign; in others, the heart ends up no longer compensating and heart failure sets in.

Key point

Respiratory distress in a dog known to have a heart condition is a life-threatening emergency: do not wait until the next day.

Commonly observed signs

These signs are neither exhaustive nor specific. Only a veterinarian can establish a diagnosis.

Related signs — each one links to its page:

Cough Difficulty breathing Rapid breathing Fatigue Reduction Loss of appetite Shortness of breath on exertion Noisy breathing or snoring

At first, no signs: the disease is discovered during a routine visit, when the veterinarian hears a murmur.

Later, a dry cough, often in the evening, at night or after exercise.

A new fatigue: the dog drags on walks, stops, demands to come home.

Faster breathing, even at rest and during sleep.

Shortness of breath for efforts that previously posed no problem.

In advanced stages, marked difficulty breathing, loss of appetite and depression, sometimes brief discomfort with loss of consciousness.

When to consult without delay

This list does not replace veterinary advice. It gathers situations that justify a prompt consultation.

Causes and risk factors

The valve gradually changes: its tissue thickens, becomes loaded with gelatinous material and loses its flexibility. The ropes that hold it stretch and can break.

It is a phenomenon of aging of the valve tissue, very largely influenced by the genetics of the breed.

No infection or particular diet is responsible; it is not a disease that the dog catches.

Age: the frequency increases markedly from maturity and concerns a large proportion of small older dogs.

Breed and size: small breeds are by far the most affected, with a marked and early predisposition in the Cavalier King Charles, and a high frequency in the Poodle, the Dachshund, the Chihuahua, the Yorkshire, the Bichon and their crosses.

The male sex is a little more represented.

A dog from young affected parents has a greater risk of developing the disease early.

Diagnosis and care

Diagnosis is the veterinarian's responsibility, based on clinical examination and laboratory tests. Care is decided case by case.

It all starts with auscultation: the breath is the first clue, and its discovery justifies an assessment even in a dog who is well.

A chest x-ray can judge the size of the heart and look for fluid in the lungs.

Cardiac ultrasound is the reference examination: it confirms the damage to the valve, measures the impact on the chambers of the heart and determines the exact stage, which determines the decision to treat or not.

An electrocardiogram is added if the rhythm is irregular, and a blood test evaluates the kidneys before any treatment.

At home, the veterinarian will often ask you to count the dog's breathing movements during sleep: this is a simple and valuable indicator for spotting worsening before visible signs.

Treatment

There is no way to repair the valve in current practice; the objective is to slow down the progression and then relieve the heart.

As long as the heart is not dilated, no medication is necessary: we monitor with regular checks.

When the ultrasound shows a heart beginning to dilate, a drug from the inodilator family is prescribed: it has been shown to delay the onset of heart failure.

When fluid accumulates in the lungs, treatment combines diuretics and medications that reduce the work of the heart, including ACE inhibitors.

A moderately reduced salt diet and maintaining a correct weight are part of the treatment.

All doses are set by the veterinarian, reassessed at each check-up, and must never be changed on your own initiative: excess diuretic damages the kidneys, abrupt stopping can trigger an attack.

Treatment depends on the cause and the animal's condition: it must be determined by a veterinarian. No self-medication.

Prevention

We cannot prevent the degeneration of the valve.

The most effective lever is selection: do not breed an affected dog at a young age, and favor lines detected in breeds at risk.

For a dog already carrying a breath, prevention consists of avoiding aggravation: healthy weight, regular exercise but without excess, regular scaling and dental care, up-to-date antiparasitic treatment, and above all respecting the frequency of checks set by the veterinarian.

Auscultation at each annual visit, and twice a year in small older dogs, makes it possible to detect the murmur before symptoms.

Possible complications

Pulmonary edema: fluid passes into the lungs and causes respiratory distress, which is an emergency.

The rupture of a valve cord, which suddenly aggravates reflux and can cause a stable dog to tip over within a few hours.

Heart rhythm disturbances, causing discomfort or loss of consciousness.

Pulmonary hypertension, which increases fatigue and shortness of breath.

More rarely, a tear in the wall of the left atrium, with a very poor prognosis.

When to see a veterinarian

Your dog breathes more than thirty to forty times per minute while sleeping, several nights in a row.

He coughs at night, or an old cough becomes more frequent.

He gets tired on walks whereas he kept up the pace not long ago.

He felt unwell, collapsed for a few seconds then got up.

He is breathing with his mouth open, his neck stretched, or his gums are turning blue: it's an emergency, go to the vet immediately.

Prognosis

A dog with a non-dilated heart murmur can live for years without any treatment or discomfort.

Once treatment is started at the right stage, the onset of heart failure is significantly delayed.

After the first episode of pulmonary edema, life expectancy is more limited, but a comfortable quality of life remains possible for several months to several years when treatment is well followed.

The prognosis depends mainly on the stage at the time of diagnosis and the regularity of checks.

Frequently asked questions

My vet heard a murmur but my dog is fine: should we be worried?

No, but you have to follow it. Many dogs live a long time with one breath without ever getting sick. An ultrasound allows you to know if the heart is starting to dilate: it is this precise stage which triggers the initiation of treatment, and treating it at the right time really changes the evolution.

How do I count my dog's breathing at home?

When he is sleeping calmly, count for one minute the number of times his chest rises. Write down the number in a notebook or your phone. A value that rises significantly over the days is a reliable warning signal, often earlier than a cough.

My dog is coughing: it must be the heart?

No way. In a small older dog, the cough can come from the heart, but also from tracheal collapse or chronic bronchitis, and all three often coexist. Only an x-ray examination can tell the difference, and the treatment is not the same.

Should we stop walking?

No. Regular, moderate exercise is beneficial. What should be avoided are intense efforts, breathless games and outings in hot weather. Let your dog set the pace and stop as soon as he slows down.