Heart Disease in Dogs
Causes, Symptoms, Diagnosis and Treatment of Heart Disease in Dogs
This article is written by Pet Circle veterinarian,
It can be very worrying when your vet detects a heart murmur in your dog at their check up, particularly if they are showing no symptoms of any problems. Heart disease can be either congenital (meaning that it is present at birth) or acquired (meaning that it develops over the life time of the dog). There are multiple causes for heart disease in dogs, and many factors such as breed, age and other health concerns can all contribute. Take a read through our guide below for the most common types of heart disease seen in dogs.
Contents:
Causes
Heartworm
Breeds Most at Risk
Symptoms
Diagnosis
Treatment
Diet
Management
Further reading
Causes of Heart Disease in Dogs
While there are multiple causes of heart disease in dogs, the most common forms diagnosed are Mitral Valve Disease and Dilated Cardiomyopathy.
Mitral Valve Disease in Dogs
Image source: PDSA UK.
Mitral valve disease is the most common heart disease diagnosed in small dogs. The heart is divided into 4 chambers - the left and right atria (the smaller chambers at the top of the heart) and the left and right ventricles (the larger chambers at the bottom of the heart). The heart functions by receiving blood into the atria, then pumping this into the ventricles, and from the ventricles out to either the lungs or the rest of the body. The atria and ventricles are divided by valves. The function of these valves is to keep blood flowing in the one direction.
The Mitral valve divides the left atrium from the left ventricle. Mitral Valve Disease (MVD)occurs when there is degeneration of the valve and this degeneration has affected its integrity, causing loss of function and this inability to adequately seal off the left atrium from the left ventricle. This causes some backflow, or regurgitation, of blood from the left ventricle into the left atrium instead of the blood flowing out into the organs. Eventually this can lead to fluid build-up in the lungs and congestive heart failure.
Dilated Cardiomyopathy
Image source: PDSA UK.
In large dogs, the more prevalent heart condition is Dilated Cardiomyopathy (DCM). Often an inherited condition, affected dogs will have weakened muscles in their heart which causes them to be unable to contract or pump blood effectively. To compensate for this, the muscles will enlarge and this will help the body for some time until ultimately, the pressure in the heart leads to fluid accumulation in the chest.
Nutritional deficiencies have also been linked to development of DCM. Dogs with taurine deficiency may later on present with DCM, as taurine is an important amino acid required for development and function of the heart. Dogs on vegetarian or vegan diets, in particular, may benefit from appropriate supplementation.
Does a Grain-free diet cause heart disease in dogs?
Many pet parents choose to go grain free in an effort to find the healthiest possible food for their pets, so naturally when the FDA announced in July 2018 that they were investigating a potential link between grain free dog food and heart disease, it's no wonder many were left wondering whether they had made the right choice.
The FDA released an update regarding their investigation into this issue on 27th June 2019 and while some common dietary factors between many of the cases have been identified, particularly the feeding of grain free diets and diets containing peas and/or lentils, the root cause is still yet to be determined. At this stage there is still no definitive evidence to link the cases to diet altogether, although identifing a specific dietary link between cases remains the primary focus of the investigation.
For more information, take a look at our article on Does Grain Free Dog Food Cause Heart Disease?
Heartworm in Dogs
Heartworm infection can also cause heart disease in dogs. It is important to worm your pet regularly. Heartworm is spread by mosquitoes and will lead to serious lung disease and heart failure. This is a fatal disease if not treated. However, treatment for heartworm can also be complicated and dangerous. Prevention is easy and always the best cure!
For more information, check out our 6 Fact You Need to Know about Heartworm.
Top Heartworm Preventatives
There are a range of products which prevent heartworm infection. Some are 'all-in-one' products, which also protect against fleas, ticks and intestinal worms. Others just protect against heartworm, or heartworm and intestinal worms. If your dog is not currently up to date with a heartworm preventative, then speak to your vet or our Vet Squad for advice prior to commencing on any product.
Simparica Trio is an all in one monthly chewie which protects against heartworm, fleas, ticks and the major intestinal worms.
Advocate is an easy to use spot on treatment applied monthly for the control of fleas, heartworm and intestinal worms.
Interceptor is a tasty monthly chewie for heartworm and intestinal worming (including tapeworm) control.
Shop All Heartworm Preventatives Now
Which Breeds Are Susceptible to Heart Disease?
A number of large dog breeds have been associated with Dilated Cardiomyopathy, most notably:
- Doberman Pinschers
- Boxers
- Standard Schnauzers
- Great Danes
- Irish Wolfhounds
- Newfoundlands
- Dalmatians
- Cocker Spaniels
- Portugese Water Dogs.
Mitral valve disease on the other hand, commonly presents in senior small dogs. The Cavalier is the most commonly affected breed, but other small breeds are often affected such as:
- Miniature Poodle
- Chihuahua
- Dachshunds
- Pomeranians
- Shih Tzu.
Symptoms of Heart Disease in Dogs
There may be little to no symptoms initially, but your veterinarian may pick up a heart murmur at an annual vaccination or health check appointment. As the disease progresses, there may be fluid accumulation in the chest leading to congestive heart failure.
- Coughing
- Lethargy
- Exercise intolerance
- Shortness of breath or trouble breathing
- Pale or blue-ish gums
- Collapse
- Fluid in the abdomen (depends on the heart condition, usually occurs with right sided heart failure)
Diagnosis of Heart Disease in Dogs
A strong suspicion of heart disease and congestive heart failure is usually made on the initial clinical exam if a heart murmur or abnormal sounds (such as fluid crackles or muffled respiratory sounds) are heard.
This may then prompt further investigation such as chest x-rays and/or referral to a cardiologist where an echocardiogram can be performed. Echocardiography is an ultrasound scan of the heart which will allow a diagnosis to be made.
Treatment of Heart Disease in Dogs
Treatment may vary and should be tailored for each individual and their specific heart condition. Many medications are available to help manage heart problems. The main goal of treatment is to improve your dog's quality of life and help them live longer.
Pimobendan is a commonly used medication for both Mitral Valve Disease and for Dilated Cardiomyopathy. This drug helps to improve the heart muscle contraction so that it may pump blood more effectively. It can also open up the blood vessels, which makes it easier for the heart to pump blood forwards. ACE inhibitors also have a similar effect and may be part of the treatment protocol.
Diuretics are often used in combination with the medications above to clear out and control accumulation of fluid in the lungs. A common first line diuretic for heart treatment is furosemide. In some cases, an additional diuretic may need be added.
It is important to bring your pet in for regular re-assessment and blood tests may be required to monitor the kidneys and electrolyte imbalances.
Nutrition for Cardiac Support
Your veterinarian may recommend a low sodium diet for your dog. Restricted sodium levels can be helpful especially with patients in more severe stages, in congestive heart failure, as this could help to reduce fluid retention. Senior-specific diets will usually contained reduced sodium compared to adult dog foods, though your vet may recommend a prescription diet for the best effect. Always consult with your vet on the best food for your pet's health.
Recommended diet for dogs with heart disease
The following diets are prescription-only diets, so it is important to check with your vet to ensure that they are appropriate for your dog.
Management of heart disease in dogs
Treatment with medications is lifelong once initiated. In addition to medical therapy, lifestyle changes are also important. For dogs showing mild symptoms or are in earlier stages, regular light exercise can be beneficial. Some dogs may require complete rest. Ask your vet for their advice on the exercise levels, and always monitor closely. If they seem tired or weak, it may be time to stop and rest.
It is often recommended to check your dogs breathing rate as they are sleeping. A general guideline is to observe whether the resting respiration rate regularly rises above 30 breaths per minute, as this could be an indication of progression of their heart disease. Life expectancy can range from several months to several years, depending on the severity and stage of heart failure.
Further reading
Premium pet food: Is it worth it?
What's the Best Senior Dog Food
How to read the label on a bag of pet food
Want to know more? Check out our Discover Page for more tips from our expert vets on keeping your pets happy and healthy.