Dog Heart Disease by Breed: Small vs Large Risks

A dog's breed and body size are key clues to heart disease risk. Small breeds tend toward degenerative valve disease (AVVI), while large breeds tend toward dilated cardiomyopathy (DCM). Here's how to monitor early.

As a veterinarian, one question I hear all the time is, "Doctor, is my dog's breed prone to heart disease?" The answer surprises many owners: your dog's breed and body size are key clues that tell us which type of heart disease they are most likely to develop. Today I'll walk you through why small breeds and large breeds face completely different cardiac risks, so we can plan the right heart care for your dog as early as possible.

In 1 Minute

Breed and body size are important indicators of which type of heart disease a dog is at risk for.
Small breeds (Chihuahua, Shih Tzu, Toy Poodle) are prone to degenerative valve disease (AVVI), or a leaky mitral valve.
Large and giant breeds (Great Dane, Doberman, Golden Retriever) are prone to dilated cardiomyopathy (DCM).
Added factors such as being male, weighing under 20 kg, and older age raise the risk of degenerative valve disease.
At-risk dogs without severe symptoms should still exercise regularly and stay at a healthy weight.
Annual check-ups and heart auscultation help catch the earliest signs before symptoms appear.

Small Breeds: Watch for Degenerative Valve Disease (AVVI)

In small-breed dogs, heart disease and heart failure most often stem from Atrioventricular Valvular Insufficiency (AVVI), better known as a leaky mitral valve.

High-risk breeds: Chihuahua, Shih Tzu, Toy Poodle, and other small breeds.
How it develops: A valve that once sealed tightly begins to thicken and deform, letting blood leak backward. This forces the heart to work harder, eventually leading to an enlarged heart and heart failure.

Part of this risk comes from genetics and the body size determined by a dog's genes, which is why smaller dogs tend to be diagnosed with this group of conditions more often.

Large and Giant Breeds: Watch for Dilated Cardiomyopathy (DCM)

For large-breed dogs, the main concern is not the valves but the heart muscle itself, a condition called Dilated Cardiomyopathy (DCM).

High-risk breeds: Great Dane, Doberman Pinscher, and Golden Retriever.
How it develops: The heart muscle thins and stretches, sharply reducing the heart's pumping strength. These dogs are at high risk of sudden, life-threatening heart failure.

Knowing whether your dog's breed falls into the DCM or AVVI risk group is valuable information. You can read more in our article on genetic diseases found across dog breeds.

Risk Factors Beyond Breed

Beyond breed, epidemiological research has identified several factors that affect the likelihood of detecting degenerative mitral valve disease (DMVD):

Factor	Effect on Risk
Gender	Male dogs are 1.4 times more likely to be diagnosed with DMVD than females.
Body Weight	Dogs weighing under 20 kg are 2 times more likely to develop it than dogs over 20 kg.
Age	The older the dog, the more clearly valve degeneration appears.

The age factor matches what I see in the clinic, because as dogs enter their senior years, heart disease often arrives alongside other chronic illnesses in senior dogs that need to be managed together.

A Common Myth and Preventive Monitoring

When owners learn their dog's breed carries a cardiac risk, many restrict activity and let their dog stay still. This is a misunderstanding.

At-risk dogs that do not yet show severe symptoms still need regular exercise and healthy weight control, because obesity is a major culprit that makes the heart work far harder.

And because heart disease often shows no symptoms in its early stages, preventive monitoring is essential.

Annual health checks: Even when your dog looks normal, a veterinarian's heart auscultation can detect a heart murmur, an important early sign.
Knowing your breed: Understanding which disease your dog's breed is prone to helps you decide on specialized tests, such as a heart ultrasound (Echocardiogram), in time.

This approach is at the heart of preventive medicine for dogs. The earlier we detect and manage the disease, while it is still in the pre-clinical stage, the greater the chance your dog will live a longer life with better quality. If you notice your dog developing a persistent cough, especially at night or after waking, tiring easily, or struggling to breathe, take them to a veterinarian right away to check the heart and lungs.

1. How does a dog's body size relate to the risk of different types of heart disease?

Body size and breed are key clues that point to different risks. Small breeds (such as Chihuahua, Shih Tzu, and Poodle) tend to be at risk for degenerative valve disease (AVVI), or a leaky valve. Large and giant breeds (such as Great Dane, Doberman, and Golden Retriever) tend to be at risk for dilated cardiomyopathy (DCM), where the heart pumps more weakly and is prone to sudden heart failure.

2. Beyond breed, what physical factors increase the risk of degenerative valve disease?

Research shows male dogs are about 1.4 times more likely to be affected than females, and dogs weighing under 20 kg are about 2 times more likely to develop the disease than larger dogs. Age is also a major factor, because the older a dog gets, the more likely the valves are to degenerate with age.

3. What foods should a dog with heart disease or at-risk dogs especially avoid?

The most important thing in a heart-disease diet is to avoid high-sodium (salty) foods such as human snacks, processed foods, and seasoned items, because sodium makes the body retain more water in the bloodstream, raising blood pressure and forcing the heart to work harder. You should also avoid foods that push weight above normal, since obesity accelerates the onset of heart failure.

4. What kind of exercise is safe for dogs at risk of heart disease?

At-risk dogs without severe symptoms can still play and exercise. Focus on gentle, gradual activities without overexertion, such as short walks or mental exercise like treat-hunting games and puzzle toys, to control weight and gently work the heart safely. But if you begin to notice signs such as a persistent nighttime cough, tiring easily, or difficulty breathing, take your dog to the veterinarian and restrict activity immediately.

References

Clinician's Brief. Dog Breeds at Risk for Heart Failure. cliniciansbrief.com
PubMed. Epidemiology of degenerative mitral valve disease (DMVD) in dogs. pubmed.ncbi.nlm.nih.gov

Written by Dr. Monticha Kitnitchee

Heart Disease by Breed: When Your Dog's Size Predicts the Risk