Sociedade Protetora
Animais de Marrocos
A Sociedade Humanitária
de Marrocos

Société Protectrice
des Animaux du Maroc

The Humane Society
of Morocco

Heart Diseases in Dogs

Heart Disease In Dogs, Causes, Diagnosis and Treatment

What are the most common heart diseases in dogs? And what treatment solutions exist?

By far the most common heart disease in dogs (75-80% of cases) is “Degenerative Mitral Valve Disease” (MVD).

This is a disease affecting the mitral valve, the “valve” which is located in the left heart, between the atrium and the ventricle. This valve, whose tissue tends to degenerate with age, gradually thickens, and, losing its elasticity, can no longer close tightly. This failure to close leads to abnormal blood flow inside the heart, which we call mitral “leaks” or “regurgitations”.

When the disease worsens, the small cords connecting the valve to the left ventricle can break; this complication can lead to pulmonary edema and other complications detrimental to the dog’s life.

A common disease in small dogs

“Degenerative Mitral Valve Disease” can appear at the age of 5 years in more than 80% of small dogs weighing less than 15 kg. In the Cavalier King Charles and the Dachshund, it is a very harmful genetic disease that can appear from the age of one year.
The disease is progressive, gradually worsening over time, more or less quickly depending on the individual. Medical treatment aimed at relieving the work of the heart and curing pulmonary edema must be prescribed as early as possible to prolong the dog’s life as much as possible.
This treatment is updated once or twice a year on a case-by-case basis through clinical, blood, and ultrasound checks at the veterinarian.
At the start of the disease, the heart carries out physiological adaptation work called the “compensatory phase”, the disease is at this stage “dormant”; When the adaptive capacities of the heart are exceeded, symptoms such as fatigue, cough, syncope appear.
The disease is said to be in its “decompensated phase”. Medications are essential here and prescribed for life unless surgery is decided at the most appropriate time in the dog’s life. Indeed, surgical treatment of “Degenerative Mitral Valve Disease” is now available with a high success rate, more than 90%. It consists of “tightening” the mitral valve that has become “too flaccid” to reduce or even eliminate leaks and then repairing the broken cords.
This is an intervention under extracorporeal circulation and requires an efficient and perfectly experienced veterinary team. After this intervention, the vast majority of small dogs are “cured” of their heart failure and no longer need to take medication. This surgical procedure is a revolution for a large number of our little dogs, whose lives we can finally save!

Large dogs: it’s the heart muscle that can pose a problem

Large dogs are also affected by “Degenerative Mitral Valve Disease”. But they are rarely as sick as the little ones. On the other hand, certain medium or large breeds are predisposed, no longer to an anomaly of the valve, but to a disease of the heart muscle, which we callMyocardiopathyand more commonly in large breed dogsMyocardiopathy Dilated.”

They account for approximately 15-20% of heart diseases in dogs. During this disease, the heart muscle becomes fragile, becomes significantly thinner, loses its contractile capacity and finally stops because it no longer has the strength to make any beats. At the same time, the heart chambers expand enormously.

The breeds for which a genetic predisposition has been determined are: the Doberman, the Cocker Spaniel, the Dalmatian, the Great Dane, the Irish Wolfhound, the Newfoundland, the Saint Bernard, the Portuguese Water Dog, the Boxer. In the latter, the disease has a particular name: “Arrhythmogenic Myopathy of the Right Ventricle”. Only medical treatment can provide relief for dogs affected by this disease, but with an often very guarded prognosis and a fairly short survival period after the appearance of the first symptoms. Surgical treatment, if one existed in dogs, would be a heart transplant as in humans. This technique is not yet developed in dogs.

Congenital heart defects can affect dogs

Finally, a small percentage of dogs (around 5%) are affected by heart disease at birth, which is called “congenital heart disease”. The most common are:

“malformations” of valves, either aortic, pulmonary, mitral, or tricuspid. Currently, all but the aortic valve can be surgically repaired in dogs, but success rates are yet to be determined. In the presence of medical treatment alone, the least severely affected dogs can survive for a few years but the time limit is generally quite short;

communications between the left heart and the right heart or between oxygenated and non-oxygenated blood. The most common birth defect is called patent ductus arteriosus. This anomaly has an excellent surgical prognosis, close to 100% if the operation is performed young enough. The puppy is then cured for life and does not take any treatment. Others, such as communication between the two ventricles for example (called “inter-ventricular communication”), are also operable but with a slightly lower success rate currently.

Puppies with congenital heart disease all have an audible heart murmur in the first few months of life. Performing an echocardiogram and a Doppler is then essential to establish a diagnosis, and a prognosis and propose the most appropriate treatment.

Dilated cardiomyopathy (an enlarged heart) in a dog can have numerous potential causes and many severe side effects. Here, we list the causes of this serious condition, symptoms, and treatment options.

What is DCM in dogs?
In dogs, an enlarged heart (also referred to as Dilated Cardiomyopathy). is a serious condition that refers to the expansion of the heart’s lower chambers (ventricles) or, less frequently, the upper chamber (atria).

The heart is unable to contract properly and push blood to the rest of the body, causing expansion. Blood builds up inside the heart before pressure is put on the heart’s valves and outer walls, expanding it. This leads to a thinning of the outer walls.

When this happens, it becomes more difficult for your pup’s heart to pump blood throughout the body, and to the organs that need it. As this condition becomes more advanced, organs such as the lungs and kidneys will begin to malfunction. The disease’s progression will eventually make dilated cardiomyopathy severe.

Causes of an Enlarged Heart in Dogs
A dog of any age or breed can have an enlarged heart, but the condition is much more common in dogs between 4 and 10 years of age.

While dilated myopathy does not have a definitive cause, many factors can contribute to the development of the condition in your pet. Nutritional deficiencies in taurine and carnitine have been proven to influence the development of an enlarged heart in dogs.

In addition, other factors such as genetics and infectious diseases can play a role in cardiomyopathy in dogs. Some dog breedsespecially large breedsare known to be predisposed to developing this condition due to taurine insufficiency. They include:

  • Newfoundland
  • American Cocker Spaniels
  • English Setter
  • Golden Retriever
  • Labrador Retriever
  • Saint Bernard

While other breeds are genetically prone to DCM, they are not linked to taurine deficiency. These include:

  • Boxers
  • Irish Wolfhounds
  • Great Danes
  • Doberman Pinschers


If your dog is one of these breeds, take more caution about what you’re feeding than the average dog owner. The longer you feed your dog the same food, the more likely he or she will be impacted by any excesses or nutritional deficiencies it contains.

Therefore, when it comes to DCM in dogs and diet issues, rotate foods regularly, changing between different brands of foods with different primary ingredients. Foods with primary ingredients of peas, potatoes, lentils, and other legume seeds have been linked to the condition.

What are the signs of DCM in dogs?
Signs of dilated cardiomyopathy in dogs may range from mild to severe as the condition progresses.

This disease is often difficult to diagnose in its early stages, as early signs of DCM in dogs do not often appear. There is sometimes a long pre-clinical phase. That said, your vet may be able to identify subtle or hidden signs of the condition during a physical examination.

This is why it’s imperative to bring your pooch to your veterinarian.

It is important to diagnose and treat challenging cases with access to numerous diagnostic tools and treatment methods.

These are some of the most common symptoms of DCM in dogs:

  • Lethargy
  • Anorexia
  • Labored breathing
  • Ofegante
  • Tosse
  • Abdominal distension
  • Sudden collapse
  • Irregular or weak pulse
  • Heart murmur
  • Muffled breathing or crackling sound while breathing


Diagnosing an Enlarged Heart in Dogs

While a routine physical examination can suggest to your vet that your pup may have an enlarged heart, a final diagnosis will require further diagnostic testing to determine if the above symptoms are a result of dilated cardiomyopathy.

X-rays
A chest x-ray of your dog may reveal abnormalities in their heart and lungs such as an unnaturally large heart or the presence of fluid in the lungs. Both of these are strong indicators of dilated cardiomyopathy.

Electrocardiogram
This test monitors the electric impulses that cause your dog’s heart to beat. This test can reveal heart issues such as an irregular heartbeat (arrhythmia) and an abnormally fast heartbeat (ventricular tachycardia) can both be detected using this method.

Echocardiogram
This diagnostic test uses ultrasound to monitor the movements and shape of your dog’s heart in real time. This test allows your vet to check your dog’s heart for tinned muscle walls and the efficacy of their heart’s contractions. This is the definitive test to determine whether your canine companion can be diagnosed with an enlarged heart or not.

Treatment of Dilated Cardiomyopathy in Dogs
Treatment may vary depending on the underlying cause of the condition in your dog. If nutritional issues such as taurine deficiency have influenced its onset, treatment may begin with dietary changes and supplements.

Treatment often involves therapies and several medications designed to strengthen your dog’s heart, which will assist with blood circulation. Dogs experiencing breathing problems due to fluid in the lungs may require oxygen therapy until the fluid drains naturally from their lungs. Your vet may also prescribe either a diuretic to drain the fluid or do this manually.

However, the condition is not reversible. It often turns progressive and there is no cure, depending on the underlying cause of your dog’s enlarged heart. In these cases, the vet will focus treatment on extending your furry friend’s life and making it as comfortable as possible.

The long-term prognosis for DCM in dogs varies considerably. Unfortunately, most dogs with signs of congestive heart failure when they are diagnosed die as a result of the disease within 6 months. In the most severe cases, some dogs may survive only weeks to a few months. Sometimes, dogs may do well clinically for 1 to 2 years.

Observação: The advice provided in this post is intended for informational purposes and does not constitute medical advice regarding pets. For an accurate diagnosis of your pet’s condition, please make an appointment with your vet.

Are you seeing signs of DCM or other illnesses in your dog? If symptoms listed here or others have you concerned, contact your veterinary team right away.

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