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Dilated cardiomyopathy in dogs

In dilated cardiomyopathy, it is the heart muscle itself that is diseased. It loses its force of contraction, the chambers expand and the heart becomes a large, soft pump that no longer sends enough blood through the body. Unlike endocardos...

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

What is it?

Unlike endocardosis, which affects small dogs, this disease mainly affects large and very large dogs, often middle-aged.

Its particularity is to be silent for a long time: the muscle weakens for months, sometimes years, before the first visible sign. This explains cases where a seemingly healthy dog collapses without warning.

Key point

Discomfort with loss of consciousness in a large breed dog should always be considered a cardiac sign until proven otherwise.

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:

Fatigue Difficulty breathing Rapid breathing Cough Weight loss Reduction Loss of appetite Swelling Shortness of breath on exertion

A long phase without any signs, where only an ultrasound can detect the disease.

Then fatigue from the effort, a dog who no longer follows, who sits while walking.

Faster breathing at rest, shortness of breath, sometimes coughing.

Weight loss with wasting of muscles, despite an unchanged diet.

A belly that swells due to accumulation of fluid, in breeds where the right heart is affected.

Discomfort or sudden loss of consciousness, linked to rhythm disturbances: the dog collapses for a few seconds then gets up, often after an effort or emotion.

Loss of appetite and marked depression in the advanced stages.

When to consult without delay

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

Causes and risk factors

In the majority of affected dogs, the origin is genetic: the heart muscle is constitutionally fragile and deteriorates over time. Several distinct hereditary forms are described depending on the breeds.

Some forms are linked to diet, notably a deficiency in taurine or L-carnitine; they are rarer but important to recognize, because they can partially regress once the deficiency is corrected. Cases have been reported in dogs fed unbalanced or atypical diets, and this avenue is still being studied.

More rarely, inflammation of the heart muscle, a hormonal disease such as hypothyroidism, or certain anticancer treatments can lead to the same picture.

Breed is the dominant factor: Doberman, Boxer, Great Dane, Great Dane, Irish Wolfhound, Newfoundland, Saint Bernard, Irish Wolfhound and other large breeds are significantly overrepresented. The Cocker Spaniel and the Spaniel are affected by forms linked to taurine.

Adult to mature, mid to late life, but early cases exist in the most affected breeds.

The male sex is more often affected and often develops a form more quickly.

An unbalanced diet, homemade without supervision or seriously unbalanced, is a factor to be corrected.

Diagnosis and care

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

Diagnosis is based on echocardiography, which shows dilated chambers and weakened contraction. This is the only test that confirms the disease.

An electrocardiogram is essential, because rhythm disturbances are common and sometimes the only ones present at the beginning. In breeds at risk, recording the rhythm over twenty-four hours can be suggested to identify them.

A chest x-ray assesses the impact on the lungs.

A blood test completes the assessment: thyroid function, kidneys, and depending on the case, taurine dosage.

In breeds with a high predisposition, annual screening is recommended in adults, even without any symptoms: this is how we save months of treatment.

Treatment

The treatment does not cure the muscle but supports the heart and significantly prolongs the dog's life.

From the silent stage detected on ultrasound, a drug from the inodilator family is put in place: it has been shown to delay the onset of heart failure.

In case of declared heart failure, diuretics are combined to evacuate the fluid and ACE inhibitors to relieve the heart.

Rhythm disorders, when dangerous, justify specific antiarrhythmic treatment chosen by the veterinarian.

If a deficiency is identified, appropriate supplementation and a return to a complete and balanced diet are an integral part of the treatment.

None of these molecules is used without prior ultrasound or monitoring: the doses are individual and readjusted regularly.

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

Prevention

For hereditary forms, prevention involves reproduction: screening breeding dogs of the breeds concerned and excluding affected dogs.

For all dogs, offer a complete and balanced diet, adapted to size and age. A homemade ration or an atypical diet should be formulated with a veterinarian to avoid deficiencies.

Maintain a healthy weight and regular activity.

In breeds at risk, an annual cardiac check-up from adulthood is the most useful measure: the disease detected in the silent stage is treated much more effectively.

Possible complications

Pulmonary edema, with respiratory distress, which is an emergency.

The accumulation of fluid in the abdomen or around the lungs, making it difficult to breathe.

Serious rhythm disturbances which can cause sudden death, particularly feared in Dobermans and Boxers.

The formation of clots in dilated cavities, with risk of obstruction of a vessel.

Muscle wasting and general weakening, the body being less well irrigated.

When to see a veterinarian

Your large breed dog tires unusually quickly or refuses to walk.

He breathes quickly at rest or while sleeping.

His stomach swells without having gained weight elsewhere.

He has felt unwell, even briefly, even once: this sign alone justifies a quick consultation.

He is breathing with his mouth open, gray or bluish gums: immediate emergency.

You own a Doberman, a Boxer or a breed at risk and he has never had a heart check-up: make an appointment without waiting for any symptoms.

Prognosis

The prognosis is more guarded than that of endocardosis, but it varies greatly depending on the race and stage.

Detected at the silent stage and treated, the disease sees its progression substantially delayed.

Once heart failure sets in, life expectancy is measured in months, with great individual variability.

Forms linked to dietary deficiency have the best prognosis: cardiac function can improve significantly after correction.

The risk of sudden death from arrhythmia exists even in a dog that appears stable, which justifies monitoring the heart rate in the breeds concerned.

Frequently asked questions

My large breed dog has no symptoms, should I still have an ultrasound?

In breeds at risk, yes. The disease remains silent for a long time and this is precisely where the treatment brings the most benefit. An annual checkup starting in adulthood is the usual recommendation for these breeds.

Could diet be the cause?

It can be in a minority of cases, particularly in cases of taurine or L-carnitine deficiency, or with an unbalanced ration. These forms are important to identify because they often improve after correction. Do not change the diet alone: talk to the veterinarian, who will be able to measure the taurine.

Can my dog die suddenly?

This is a real risk in certain breeds, linked more to rhythm disturbances than to muscle weakness. This is the reason why the veterinarian suggests an electrocardiogram, sometimes over twenty-four hours: an identified rhythm disorder can be treated.

Can I still play sports with him?

Intense efforts, running and playing out of breath should be stopped as soon as the diagnosis is made. Quiet walks are still recommended. Your veterinarian will specify the activity level depending on the stage.