7 Common Heart Problems in Dogs [+Signs, Causes & Prevention]

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About 10-15% of dogs suffer from some type of cardiac disease. While some conditions are congenital or present at birth, most (95%) of heart problems are acquired during a dog’s lifetime.

Heart problems that commonly affect dogs include:

  • Atrioventricular valve disease
  • Dilated cardiomyopathy (DCM)
  • Heartworm
  • Pericardial disease
  • Congestive Heart Failure
  • Shunts
  • Stenosis

Common Heart Problems

Unfortunately, dogs suffer from heart disease almost as much as humans. By understanding the common conditions, you’ll be more prepared to recognize trouble and seek treatment early for the best possible outcome.

Mitral valve disease

In mitral valve disease, the valve that regulates the normal flow of blood from the left atrium to the left ventricle malfunctions, allowing some blood to flow backward. As the valve thickens and stiffens, it becomes more leaky and causes the heart to be less efficient.

As an acquired condition, mitral valve disease takes time to develop and become symptomatic. It is usually diagnosed in adult dogs.

Signs of mitral valve disease include:

  • Heart murmur
  • Exercise intolerance
  • Cough
  • Breathing difficulty
  • Increased respiration rate
  • Loss of appetite
  • Difficulty resting comfortably

The cause of degenerative mitral valve disease is not fully understood, but there appears to be a genetic component. In some cases, a rupture of the valve tendons can cause mitral valve disease. Small breed dogs, including Cavalier King Charles Spaniels, Chihuahuas, Fox Terriers, Yorkshire Terriers, Pomeranians, Miniature Poodles, and Dachshunds, are predisposed to developing the condition.

If mitral valve disease goes untreated, the valve can become more leaky, thus causing the heart to become less efficient.  As a result, the cardiac muscle thickens to compensate. Over time, dogs may suffer from heart failure.  

The best way to prevent mitral valve disease in your dog is through selective breeding. You can also feed your dog a balanced diet to help him maintain a healthy weight that places less strain on the heart.

Treatment of mitral valve disease in dogs varies depending on the stage or severity of the condition. Early-stage disease can be monitored, and dogs can be placed on a heart-healthy diet. In more advanced stages, your veterinarian will prescribe diuretics and cardiac drugs to improve heart strength and function and reduce blood pressure.

Dilated cardiomyopathy (DCM)

Dilated cardiomyopathy (DCM) is a condition in which the heart grows larger and the muscle becomes thinner and weaker.

Because DCM is a progressive, acquired disease, it takes time to develop in dogs. The age of onset is usually between 3 and 7 years.

Signs of DCM include:

  • Rapid, difficult breathing
  • Restlessness
  • Wet cough
  • Exercise intolerance
  • Weakness and lethargy
  • Loss of appetite
  • Bluish mucous membranes
  • Fainting

Causes of DCM in dogs may include infections, nutrition, and genetics. It appears to occur more commonly in certain large breeds, including Doberman Pinschers, Irish Wolfhounds, Newfoundlands, Boxers, and Great Danes.

Without treatment, DCM usually causes congestive heart failure, decreased quality of life, and premature death.

Preventative measures for DCM include selective breeding, avoiding boutiques, eating grain-free diets, and supplementing with vitamins and minerals that support heart health.

Treatment for DCM involves medical management with drugs to increase the heart’s efficiency and reduce the burden on the muscle. 


Heartworm disease occurs when the parasite Dirofilaria immitis clogs the pulmonary vessels or the heart and interferes with circulation. 

The heartworm parasite can infect dogs at any age.

Signs of heartworm disease in dogs include:

  • Cough
  • Exercise intolerance
  • Lethargy
  • Weight loss 
  • Panting or labored breathing
  • Collapse
  • Sudden death

Dogs become infected with heartworm when a mosquito that carries the larvae deposits it while taking a blood meal. The larvae then migrate through the dog’s body until they arrive in the heart and grow to adulthood.

Without treatment, adult heartworms can reproduce and overwhelm the heart, leading to congestive heart failure and death.

Prevention of heartworm disease in dogs involves annual blood tests to screen for the disease and monthly antiparasitic medications.

Treatment for heartworm disease starts with exercise restriction and supportive care to stabilize your dog’s condition. When your dog is ready, the multi-step regimen in which your veterinarian will inject a drug to kill the adult heartworms and administer antibiotics. The injections are repeated a month later, and then drugs are given to kill the larvae. Depending on the severity of the infection, the prognosis is guarded.

Pericardial disease

When the sac surrounding the heart becomes stiff or fills with fluid, it interferes with the heart’s ability to pump blood effectively.

Middle-aged dogs are most likely to develop pericardial diseases.

Signs of pericardial disease include:

  • Rapid/difficult breathing
  • Exercise intolerance/lethargy
  • Gagging/vomiting
  • Pale gums
  • Loss of appetite
  • Ascites 
  • Collapse

Various factors can cause pericardial disease, including tumors, clotting disorders, toxins, congestive heart failure, infections, or low blood protein. Large-breed dogs, including Great Danes, Labrador/Golden Retrievers, German Shepherds, Saint Bernards, Bulldogs, and Boxers, are predisposed to develop pericardial disease.

Without treatment, pericardial disease can cause death. This condition is a medical emergency.

Prevention of pericardial disease includes selecting puppies with no familial history of heart problems and treating any underlying conditions that could cause pericardial disease.

Treatment for pericardial disease usually involves treating the underlying condition. If the heart can’t pump properly, treatment includes removing fluid from the pericardial sac to relieve pressure on the heart.

Congestive Heart Failure (CHF)

Congestive Heart Failure (CHF) occurs when the heart can’t pump blood effectively to the rest of the body. 

CHF occurs most often in middle-aged to older dogs. However, some puppies and young adults can develop congestive heart failure if they have a congenital heart condition.

Signs of congenital heart disease include:

  • Coughing, sometimes with foam
  • Labored breathing.
  • Increased respiratory rate
  • Exercise intolerance
  • Lethargy and fatigue
  • Blue gums
  • Distended abdomen/ascites
  • Collapse or sudden death

Causes of congestive heart failure include mitral valve disease, congenital defects, pericardial disease, DCM, heartworm disease, and heart tumors.

When dogs don’t receive treatment for CHF, they will have a decreased quality of life and a shorter lifespan.

To prevent CHF in dogs, schedule regular checkups with your veterinarian, feed a balanced diet that supports heart health, and treat any underlying conditions that can cause CHF.

Treatment for CHF varies depending on the severity and cause but will include diuretics to reduce fluid retention in the lungs and other body tissues and a low-sodium diet. Your veterinarian will also prescribe other cardiac drugs to treat the underlying cause and support heart function.

Shunt/Patent Ductus Arteriosus

Shunts are congenital defects, such as patent ductus arteriosus(PDA), that interfere with normal blood circulation. The ductus arteriosus is open during gestation to let blood bypass the lungs, but it usually closes shortly after birth. 

Shunts are present at birth and can cause significant problems in puppies.

Signs of PDA include:

  • Loud heart murmur
  • Difficulty breathing
  • Exercise intolerance
  • Stunted growth
  • Sleeping a lot

PDA is more common in female dogs and appears to have a genetic link. Some breeds, including Pomeranians, Maltese, English Springer Spaniels, American Cocker Spaniels, Shetland Sheepdogs, German Shepherds, Newfoundlands, Labrador Retrievers, and Irish Setters are predisposed to PDAs. 

Leaving a PDA untreated places a burden on the heart that can cause pulmonary hypertension, congestive heart failure, and death.

Prevention of PDAs focuses on selective breeding to cull any stock with a history of PDAs. 

Treatment of PDAs focuses on closing the shunt. Depending on the severity of your dog’s condition, a cardiac specialist may perform surgery to tie off the duct or insert a blocking device via heart catheterization.


A stenosis is a narrowing of an area around the heart valve that restricts normal blood flow. The narrowing can affect the aorta or pulmonary vein.

Puppies are born with the condition, which is usually detected during a juvenile physical exam.

Some dogs won’t show outward signs of stenosis. More severe cases may display observable symptoms, including:

  • Mild to severe murmur
  • Lethargy
  • Exercise intolerance
  • Fainting or collapse
  • Ascites

Stenosis is a congenital condition with a genetic component. Predisposed breeds include Newfoundlands, Bullmastiffs, Boxers, Golden Retrievers, Rottweilers, Bulldogs, and Beagles.

Mild cases of stenosis may only need monitoring without treatment. However, leaving moderate to severe stenosis untreated places a burden on the heart that can cause changes in the muscle and eventual congestive heart failure.

To prevent stenosis in dogs, refuse to breed stock that carries the condition.

Treatment for stenosis may include drugs that help increase heart efficiency or balloon catheterization to stretch the valve tissue and enlarge the opening.

Heart Health Problems across the lifecycle

Dogs can experience heart health issues at various stages in their lives. For example, congenital conditions like PDA are present from birth, while other problems like CHF usually appear later in life.

Heart Health Problems in Puppies

The most common heart health problems that affect puppies are congenital defects. When the ductus arteriosus fails to close after birth, puppies will develop symptoms of a PDA. Stenotic valves are also present at birth and are usually detected in puppies.

Heart Health Problems in Adult Dogs

Many acquired heart health problems take time to develop and manifest in adults. Mitral valve disease is usually diagnosed in adults, and the average age of dogs diagnosed with DCM is 3-7 years. 

Some other conditions like heartworm disease and pericardial disease may affect dogs at any age but are more likely to manifest during the adult years. 

Heart Health Problems in Senior Dogs

Heart health issues in senior dogs are usually caused by cumulative effects of other conditions. Congestive heart failure often surfaces in middle-aged or senior dogs after years of stress on the heart muscle.

Heart Problem Signs Dog Parents Should Beware of

Many heart problems in dogs share common signs. If you see the symptoms listed below, contact your veterinarian and schedule a checkup for your furbaby.

  • Heart murmur
  • Exercise intolerance
  • Cough
  • Breathing difficulty
  • Restlessness
  • Loss of appetite
  • Bluish mucous membranes
  • Weight loss 
  • Fainting/collapse
  • Ascites 
  • Stunted growth

Common Causes of Heart Problems

While many heart conditions have a genetic component, there are other contributing factors.

  • Genetic predisposition
  • Nutrition/diet
  • Infections
  • Parasites
  • Tumors
  • Toxins
  • Other heart conditions

Heart Health Care Tips and Problem Prevention

Taking the best possible care of your dog’s heart includes some preventative measures and basic health care practices.

  • Work with a reputable breeder who won’t use stock with heart health issues.
  • Feed a balanced diet that supports heart health
  • Give your dog monthly heartworm preventative medicine
  • Keep your dog at a healthy, lean body weight
  • Provide appropriate daily exercise for your dog based on his breed and health
  • Schedule annual health checkups for your dog

The Final Woof

1 in 10 or more dogs will deal with some form of heart disease in their lifetime. Understanding the common conditions can help you identify trouble in your pooch and seek care as soon as possible. Depending on the issue, heart problems may affect your dog at any stage of life. Fortunately, you can take preventative measures and follow healthcare practices to help protect your pooch.

Photo of author
Dr. Libby Guise earned her DVM from the University of Minnesota in 1994. After working in private practice in Wisconsin for two years, she joined the USDA as a Veterinary Medical Officer. In 2011, Libby came home to focus on raising and teaching her adoptive daughter. She lives in Wisconsin with her daughter, husband, and two furbabies: Charis, a lab-mix rescue pup, and Chesed, a Springer Spaniel.

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