Heart Disease in Dogs

Heart disease is the umbrella term to describe a wide range of conditions that affect the heart. Some of the most common types of heart disease in dogs include mitral valve disease, dilated cardiomyopathy and atrial fibrillation. Heart disease is often caused by a leaking valve, a vessel that is too narrow, or a change to the shape or thickness of the heart chamber. In this blog, we’ll explore some of the common types of heart disease in dogs, detail the symptoms to look out for, and how the conditions can be managed.

Symptoms of Heart Disease in Dogs

Heart problems can cause a range of symptoms. Some of the ones to look out for include:

  • Low energy
  • Reduced tolerance for exercise, or slowing down on walks
  • Coughing
  • Collapsing
  • Difficulty breathing (breathing may sound heavy) or excessive panting
  • Weight loss
  • Swollen belly

If you spot any of these symptoms, you should make an appointment to see your vet. Symptoms are not always noticeable until dogs go on to develop heart failure, which is why regular check-ups at the vet are so important.

Your vet will be able to use a stethoscope to listen to your dog’s heart. If they identify signs of heart disease, most commonly a heart murmur or irregular rhythm, they will advise further investigation.

There are many different types of heart disease, so before your pet can be treated, your vet needs to work out exactly what the problem is. While a stethoscope can help a vet identify the character, loudness and location of a murmur, only a heart scan can provide a definitive diagnosis.

Types of Heart Disease

Following diagnostic tests, which may include general blood tests, an ultrasound scan of the heart (known as an ‘echocardiogram’ or ‘echo’ for short), blood pressure measurement, ECG, or X-ray, your vet or specialist cardiologist will be in a better position to make a diagnosis.

Some of the most common types of heart disease in dogs include:

Dilated Cardiomyopathy (DCM)

Dilated Cardiomyopathy is a form of heart disease where the heart muscles stretch and become overly large. This makes them weak and floppy, so that they are less effective at pumping blood.

DCM is most common in middle-aged and older dogs, particularly larger breeds like Dobermans, Irish Wolfhounds and Great Danes.

Mitral Valve Disease (MVD)

Degenerative mitral valve disease is the most common form of heart disease in dogs.

The mitral valve is one of four valves in the heart that, when healthy, allows blood through in one direction and seals quickly to prevent any blood leaking backwards.

In MVD, the mitral valve can become thickened and lumpy, preventing it from being able to shut properly. The resulting leakages means the heart has to work harder to make sure enough blood reaches the body with each heartbeat. It also gradually causes the chambers of the heart to stretch, reducing the heart’s efficiency even further.

MVD is more common in small breeds like Dachshunds, Cavalier King Charles Spaniels, and some breeds of terrier.

Atrial Fibrillation

An arrhythmia is an abnormal heart rhythm, where the heart beats either too quickly, too slowly or in an irregular pattern. The most common arrhythmia in dogs is atrial fibrillation.

Atrial fibrillation is where the top two chambers of the heart generate their electrical signals too quickly to fully contract as they should, which causes them to quiver at an extremely fast rate.

While not all of these electrical impulses will be transmitted, atrial fibrillation still causes a very fast, irregular heart rate. It’s often so fast in fact, that the heart cannot completely empty and refill itself with every beat, resulting in less blood getting pumped around the body.

Other types of heart disease include congenital heart disease, which is an umbrella term for a range of different types of heart disease that a puppy is born with, and pericardial disease, which is where something goes wrong with the pericardium, the thin membrane that sits around the heart.

Congestive Heart Failure in Dogs

All types of heart disease reduce the heart’s ability to do its job effectively. Therefore, heart disease can eventually lead to something called congestive heart failure.

This is a condition where the heart valves, which usually regulate the flow of blood to and from the heart, stop working properly.

When the heart is not pushing enough blood out around the body, the pressure within the heart increases. Usually, it will be the left side of the heart that is affected. When this happens, the blood vessels in the lungs become unable to empty into the main vessels entering the heart, which causes congestion to develop there. Fluid leaks from the blood vessels into the lung tissue, known as pulmonary oedema.

Less commonly, the right side of the heart is affected. This causes congestion in the veins in the abdomen, and can lead to fluid accumulating in the abdomen (known as ascites) and chest cavity around the lungs (known as pleural effusion).

It is uncommon for left and right-sided heart failure to develop at the same time, though in severe cases, one can lead to the other.

Often dogs with suspected congestive heart failure will already have a known heart problem that’s been previously diagnosed. Dogs with left-sided congestive heart failure may display any of the same symptoms of heart disease listed above, including difficulty breathing and exercising, weight loss and collapse.

Dogs with right-sided congestive heart failure may experience difficulty getting comfortable, reduced appetite, a need to urinate more or a swollen belly.

How is Heart Disease Treated in Dogs?

Treatment will depend on the type and severity of your dog’s heart disease.

The early stages of mitral valve disease do not require treatment, but dogs with this condition will need to be regularly monitored for any changes. This usually includes a check-up every 6-12 months, sometimes with an echocardiography (commonly called an ‘echo’), which is an ultrasound of the heart. Dogs with more advanced mitral valve disease will require medication to help the heart pump effectively.

It is recommended that dogs who are diagnosed with dilated cardiomyopathy start daily treatment with a medicine that helps the heart to pump effectively. This medication may also delay the development of congestive heart failure. Dogs with dilated cardiomyopathy will also require regular check-ups and heart scans every 3-6 months.

Atrial fibrillation is also managed through medication and regular check-ups. Dogs who are very unwell or have collapsed might need to stay in the clinic until the arrhythmia is under control.

Congestive heart failure always requires treatment, and it’s a progressive disease which means dogs will need to be on lifelong medication. More than one medication may be prescribed, and which ones will depend on your dog’s individual circumstances, but the most important medication for dogs with congestive heart failure are diuretics. These relieve the fluid build-up in the lungs. Diuretics can be taken orally at home, or they are administered by injection at the vets.

As with the other forms of heart disease, regular monitoring is essential for a dog with congestive heart failure, which may consist of repeat echos and sometimes chest x-rays to assess the lungs.

Managing Your Dog’s Heart Disease

Scheduling regular check-ups with your vet is essential to managing any form of heart disease in your dog. They will be able to check that your dog is receiving the right doses of medication, and carry out scans to assess the condition of your dog’s heart.

For dogs with congestive heart failure, one of the best ways to monitor your dog’s condition at home is to measure their respiratory rate (breathing rate). When your dog is calm and relaxed, count how many breaths they take in 15 seconds (in and out is one breath). Multiply this by four to get a respiration rate per minute. Healthy dogs take less than 30 breaths per minute. Contact your vet if your dog’s respiratory rate is repeatedly over 40, or you see a steady increase over several days.

Your vet may also recommend a special diet for your dog to help support cardiac function. Royal Canin and Purina both offer specially formulated diets for dogs with heart conditions, which contain optimal levels of taurine, omega-3 fatty acids and other essential nutrients for heart health, as well as restricted sodium levels.

How Long Can a Dog With Heart Disease Live?

It’s not possible to predict exactly how long a dog with heart disease or heart failure will live because each case is very different. The prognosis will depend on the type of heart disease, how progressed it is and whether it’s likely to progress further, and whether or not they respond well to treatment.

Some dogs remain stable on medication for the rest of their life, while others may stop responding to treatment.

Wrapping Up

There are lots of different types of heart disease in dogs, with many of them causing the same kinds of symptoms. While any dog can develop heart disease, it’s particularly common for certain breeds. Cavalier King Charles Spaniels, dachshunds and some terriers are more prone to mitral valve disease for example, while giant breeds like Great Danes and dobermans are more at risk of dilated cardiomyopathy. Many types of heart disease can be managed well, especially if caught early, so recognising the symptoms of heart disease in dogs can make a big difference.

Animed Veterinary Nurse, Beth Walker
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