Heart disease in dogs

Heart disease in dogs infographic

How do dogs get heart disease, what are the symptoms to watch out for, how do you know if your dog is affected, which breeds are most at risk, and what are the treatment options?

Dogs, much like humans, can be at risk from a range of heart diseases. Understanding the differences between the common types, including their risk factors and symptoms, can help you to identify them early on and manage them effectively, ultimately enhancing your dog’s outcome and overall well-being.

What is heart disease?

Heart disease is a broad term used to describe a range of abnormalities that affect the heart’s normal function, ranging in severity from mild to life-threatening. These can either be congenital (present at birth) or develop later in life due to genetic risk factors or environmental reasons.

At birth (or congenital) diseases

While congenital heart diseases in dogs are fortunately rare, here are some of the most common types:

Aortic, subaortic and pulmonic stenosis

Aortic stenosis (AS) and subaortic stenosis (SAS) involve the narrowing of the aortic valve, which restricts blood flow from the heart to the rest of the body. Similarly, pulmonic stenosis (PS) is where the pulmonary valve is narrowed. As this valve if found between the right ventricle and the main artery leading out of the heart to the lungs, pulmonic stenosis causes a restriction of blood flow through the heart.

These conditions increase blood pressure within the heart, which causes the heart to enlarge and become less efficient. Left untreated, they can cause exercise intolerance, lethargy, breathing difficulties, fainting, congestive heart failure, and even sudden death.

Atrial septal defects (ASD) and ventricular septal defects (VSD)

These birth defects are abnormal ‘holes’ within the walls of the heart. ASDs affect the atrial wall, whereas VSDs affect the ventricular wall. These openings disrupt the heart’s normal blood circulation, resulting in a range of symptoms depending on the size and location of the hole.

Patent ductus arteriosus (PDA)

This rare congenital heart condition develops when a foetal blood vessel, known as the ductus arteriosus, fails to close after birth, causing an abnormal blood flow between the aorta and the pulmonary artery. This puts strain on the heart, and over time, can lead to congestive heart failure if left untreated.

Adult-onset (or acquired) diseases

Here are some of the most common types of acquired heart disease in dogs:

Mitral valve disease (MVD)

Mitral valve disease (MVD) is the most common acquired heart disease among dogs, particularly in small breeds such as the Cavalier King Charles Spaniel. The condition is due to the mitral valve becoming less effective at passing blood into the correct chamber, and essentially “leaks” blood backwards in the wrong direction. Because of this, the heart must work harder to circulate blood throughout the body. As the valve leakage worsens, it can lead to the heart enlarging and becoming less efficient, ultimately resulting in breathing difficulties and congestive heart failure.

The Kennel Club Heart Scheme assesses Cavalier King Charles Spaniels for MVD and other potentially significant heart diseases. This thorough examination involves using a stethoscope to listen to the dog’s heart for signs of a murmur and an echocardiographic scan to assess valve integrity. Specially-trained cardiologists use a pre-defined protocol to determine the severity of any detected abnormalities. This grading system is used to advise owners if their dog is affected by heart disease and to provide guidance to breeders on how to lower the risk of producing affected puppies. Although this scheme is currently only available for the Cavalier King Charles Spaniel, it is hoped to be expanded to additional breeds in the future. For details of The Kennel Club Heart Scheme, please visit Cavalier King Charles Spaniels Scheme page

Dilated cardiomyopathy (DCM)

Dilated cardiomyopathy (DCM) is the second most common acquired heart disease among dogs, typically developing later in life and most commonly found in large and giant breeds. This degenerative disease is characterised by the heart enlarging, and becoming less elastic within the heart’s lower chambers (ventricles), which in turn reduces its ability to pump blood throughout the body. Life expectancy varies depending on the individual and the extent of heart damage.

Atrial fibrillation (AF) is an irregular heart rhythm leading to reduced efficiency. While some affected dogs may present with no clear symptoms, certain breeds, such as the Irish Wolfhound, may experience AF as a precursor to DCM.

Arrhythmogenic right ventricular cardiomyopathy (ARVC)

Arrhythmogenic right ventricular cardiomyopathy (ARVC) causes normal heart muscle to be replaced by fatty fibrous tissues. Dogs affected by ARVC typically show symptoms such as fast abnormal heart rhythms (tachyarrhythmias), fainting, and in severe cases, sudden death. Boxers and some bull breeds such as Bulldogs have been known to be affected by this condition.

What causes heart disease?

The development of heart disease is influenced by various factors including age, genetics, lifestyle, and other health conditions.

While we do not yet fully understand how heart disease is inherited in the majority of breeds, it is likely very complicated, involving multiple different genes and environmental factors. The hereditary component of heart disease is part of ongoing research.

How can I tell if my dog has heart disease?

Symptoms of heart disease in dogs vary depending on the type and severity of the specific condition. These may include a blue or grey tinge to their gums (meaning your dog has low blood oxygen levels), persistent coughing, difficulty breathing, not wanting to exercise, lethargy, and general weakness. If left untreated, severe cases can escalate to abnormal heart rhythms, fainting, congestive heart failure, and even sudden death. Prompt veterinary attention is crucial for dogs exhibiting any of these symptoms.

What age does heart disease normally develop?

As each heart disease is influenced by a range of factors that affect the heart in different ways, there will be different ages depending on the type of disease. Symptoms of congenital (present from birth) heart disease typically show during puppyhood or in younger dogs, whereas symptoms of acquired (adult-onset) heart disease may not become clear until the dog reaches middle age or older.

What breeds are affected by heart disease?

Heart disease is seen across dogs and breeds, however some breeds are known to be at a higher risk of specific conditions. The following lists provide a general overview and may not include every affected breed. It is important to note that heart disease is also not limited to purebred dogs and can affect crossbreeds too.

Breeds known to be affected by:

  • Aortic stenosis/ subaortic stenosis (SAS) include the Boxer, Bullmastiff, Bull Terrier, Bull Terrier (Miniature), and Newfoundland.
  • Atrial fibrillation (AF) include the Irish Wolfhound and Newfoundland.
  • Atrial septal defects (ASD) include the Boxer.
  • Patent ductus arteriosus (PDA) include the German Shepherd Dog and Newfoundland.
    • Pulmonic stenosis include the Boxer, Bulldog, and French Bulldog.
    • Mitral valve disease (MVD) include the Chihuahua (both varieties), Cavalier King Charles Spaniel, Dachshund (all varieties), Havanese, and Whippet.
    • Dilated cardiomyopathy (DCM) include the Deerhound, Dobermann, Dogue de Bordeaux, Great Dane, Irish Wolfhound, and Newfoundland.
    • Arrhythmogenic right ventricular cardiomyopathy (ARVC) include the Boxer and Bulldog.

How is heart disease diagnosed?

Veterinary diagnosis involves a range of examinations, including physical assessment, blood tests, blood pressure measurements, auscultation (stethoscope examination to detect any abnormal rhythms or sounds in the dog’s heart and lungs), and imaging techniques such as chest radiographs and echocardiography (ultrasound of the heart).

How do I test for heart disease?

Always speak to your vet if you are concerned about your dog’s heart. If necessary, they may recommend a referral to a veterinary cardiologist. These specialists have undergone advanced training to diagnose and treat heart disease in animals with a high level of expertise. For a list of accredited veterinary cardiologists, please visit the Veterinary Cardiovascular Society’s (VCS) website here.

For those considering breeding a Cavalier King Charles Spaniel, there’s an official screening scheme for detecting heart disease within this breed. More information about this screening scheme can be found on Cavalier King Charles Spaniels Scheme page.

What treatment options are available for heart disease?

Treatment for heart disease is tailored to the specific type and severity of the condition. Therefore, it's important to promptly seek veterinary attention if you observe any signs associated with heart disease in your dog.

Treatment aims to manage symptoms, improve heart function, and slow disease progression. Depending on the individual case, a combination of medications, surgical interventions, and lifestyle adjustments (such as changes to your dog’s diet or exercise regime) may be recommended. Such medications may include diuretics to reduce fluid retention, angiotensin converting enzyme (ACE) inhibitors to reduce blood pressure by dilating blood vessels, beta-blockers to regulate heart rate and blood pressure, and inotropic drugs to change the force of the heart’s contractions. You should always consult with your vet before giving any supplements.

Can heart disease be cured?

It is important to discuss the long-term prognosis and treatment options with your veterinarian.

Can I breed from my dog if they have heart disease?

If a dog is affected by heart disease, we do not recommend that this dog is used for breeding. By using this dog for breeding you may be putting any puppies produced at risk of developing the condition and you could be perpetuating “risky” genes within the breed as a whole. For more information about inherited conditions where no test is yet available please visit Inherited conditions with no tests page

Unfortunately, as the inheritance and development of heart disease is complex, there is no guarantee against producing affected puppies. However, through available screening schemes and responsible breeding practices breeders can reduce the risks and be aware of their breeding dogs’ heart status before breeding.

What can I do to prevent heart disease?

Heart disease can significantly impact a dog’s quality of life if not properly managed. Thus, both early detection and intervention play a crucial role in providing your dog with the best opportunity to manage or overcome their condition. Therefore, ensuring regular veterinary check-ups, providing a balanced diet, and promoting a healthy lifestyle can reduce the risk of heart disease and improve your dog’s overall well-being.

Can heart disease cause other problems?

Heart disease can result in secondary complications that impact other organs and systems within the body. Therefore, early detection, effective management, and consistent veterinary care are essential for managing these complexities, improving outcomes, and ultimately enhancing the dog’s quality of life.

Where can I find further support and resources?

For additional support, we encourage you to reach out to your veterinarian. You may also find it helpful to contact your breed health co-ordinator, or members of your local Breed Club, for any breed-specific guidance and advice.


Can I contribute to any research?

Owners can contribute to ongoing research efforts by staying informed about current projects. Please visit our research page here to see current projects that apply to your breed.

Find a vet near you

If you're looking for a vet practice near you, why not visit the Royal College of Veterinary Surgeons' Find a vet page.

Think your dog may be affected?

If you're worried about your dog's health, always contact your vet immediately!

We are not a veterinary organisation and so we can't give veterinary advice, but if you're worried about any of the issues raised in this article, please contact your local vet practice for further information