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Early Signs of Heart Disease in Dogs

Developed in collaboration with Andrea Johnson, DVM | Co-Founder | PetVet365

Last reviewed: March 15, 2024

Detecting heart disease in dogs can be challenging, especially in its early stages. That's why it's crucial to be familiar with the early signs and symptoms of canine heart disease.

Heart conditions are quite prevalent in dogs, with the CVCA reporting that 35% of senior dogs and approximately 10% of all dogs are affected by some form of heart disease or condition. Identifying the problem early on and seeking treatment can significantly improve the chances of a positive outcome.

While there is no cure for heart disease in dogs, medication and lifestyle adjustments can help manage the condition. In this article, we will outline the most common symptoms, types, and treatments of cardiovascular conditions in dogs, along with valuable tips on how you can take preventive measures.

Key Facts
  • “Heart disease” is a broad term that refers to a wide range of heart-related problems that can affect your dog.
  • There are a number of heart conditions that your dog can have. Symptoms for all of them are similar.
  • Heart disease can be inherited (congenital) or acquired through poor diet, infections, parasites, and other factors.
  • Some dog breeds are more prone to heart disease than others.
  • Treatment usually consists of a combination of cardiac medications and, occasionally, surgery.
  • Some heart conditions can be prevented or delayed.

What is Canine Heart Disease?

“Heart disease” is a broad term that refers to a wide range of heart-related problems that can affect your dog. Some are minor and can be corrected with lifestyle changes. Others are life threatening and require immediate veterinary medical treatment. Depending on the severity of the condition, your veterinarian may refer you to a board-certified veterinary cardiologist.

Spotting Early Heart Disease Symptoms in Dogs

Heart disease frequently affects dogs, just like humans, often resulting from various underlying issues like arrhythmia, heart muscle illness, or heart valve degeneration. Despite the numerous kinds of heart diseases dogs may suffer from, owners can usually spot some shared symptoms signaling a potential problem.

Persistent Coughing
If your dog can't shake off a cough within a few days, it might be due to heart disease. Dogs with heart disease cough for assorted reasons. Sometimes, when the heart isn't pumping blood efficiently, fluid can build up in the lungs. This excess blood causes fluid leaks from the blood vessels, accumulating in the lung tissue and causing a cough. 

Other dogs could have heart conditions that enlarge the heart size, leading to pressing on the airways and inducing coughing. Any persistent cough lasting more than just a couple of days should have a veterinarian checkup.

Fainting or Collapsing
If a dog's heart isn't working effectively, vital organs like the brain may lack essential nutrients, particularly oxygen. Blood flow to the brain could be compromised in dogs with heart disease, leading to a fainting spell (syncope) or even collapse. Syncope and collapses usually happen during exercise or sometimes coughing in dogs with heart disease.

Difficulty Breathing / Change in Breathing Rate
Dogs suffering from heart disease often struggle with breathing (dyspnea). You might notice your dog breathing faster, harder, or stretching its neck out while sitting or standing with its legs wide apart. Dogs with severe heart disease typically have breathing difficulties when lying down and will often remain standing or sitting for long periods.

Fatigue, Unable to Exercise
Heart disease can cause dogs to get tired quickly during walks or other exercise. You may notice they sleep or rest more than usual.

Behavior Changes
You might also observe changes in your dog's behavior due to heart disease. Symptoms may include a decreased appetite, isolating themselves, or displaying reluctance to play or partake in activities they previously enjoyed.
Heart disease symptoms in dogs can often resemble those of other ailments such as arthritis, seizures, or chronic lung disease. However, a knowledgeable veterinarian can identify the correct diagnosis through detailed history and necessary diagnostic tests.

10 Common Types of Heart Disease and Heart Failure in Dogs

As mentioned earlier, “heart disease” is a broad term that refers to a wide range of cardiovascular problems that can affect your dog’s heart health and lead to death. Some of the more common heart conditions are:

  1. Left-Sided Congestive Heart Failure: This is the most common type of congestive heart failure (CHF) in dogs. The left side of the heart collects oxygen-rich blood and pumps it out to the body’s organs. When the upper and lower left side chambers are compromised or fail, fluid accumulates within the lungs (pulmonary edema). Dogs with left-sided congestive heart failure often faint due to lack of blood flow and oxygen to the brain. They may also have a low heart rate and low blood pressure.
  2. Right-Sided Congestive Heart Failure: If the right side of the heart is weak or has a dysfunctional valve, the heart is unable to pump enough blood to the lungs for oxygenation. Pressure builds up in the vessels that deliver blood to the right atrium and to the body’s veins and capillaries. This can cause fluid buildup in the abdomen (ascites). Fluid may also leak from veins in the limbs and cause swelling (peripheral edema).
  3. Mitral Valve Disease (MVD): Mitral valve disease is a problem with one of the valves inside the heart. It’s particularly common in small breeds.
  4. Dilated Cardiomyopathy (DCM): Dilated cardiomyopathy is a weakness in the heart muscle that causes the heart to become large, floppy, and unable to pump blood properly. DCM is most common among large/giant breed dogs.
  5. Myocardial Disease: When a dog’s heart muscles thicken and become weak. This makes the heart less efficient at pumping blood through the circulatory system. Myocardial disease cannot be cured, but it can be managed with proper nutrition and exercise.
  6. Pericardial Disease: When the pericardial sac becomes over-filled with fluid, making the heart work harder and less efficiently.
  7. Valvular Disease: When the valves within your dog’s heart are abnormal, which causes leaking and an enlarged heart. It is often an early sign of congestive heart failure (CHF).
  8. Arrhythmia or Heart Murmur: An irregular heartbeat or heart rhythm is when the heart beats abnormally and does not circulate blood efficiently. This usually means that the valves of the heart are not working properly. It is usually caused by another heart condition or old age. Young dogs can have innocent murmur that they outgrow quickly.
  9. Dilated Cardiomyopathy: An enlarged heart. Usually a symptom of an underlying heart condition. Can be genetic in cause or diet related (such as the recent grain free diet cases).
  10. Congenital Heart Disease: A heart disease your dog was born with, possibly inherited from one of their parents. And while it may not always be a problem, as your pet ages, it can lead to many other heart conditions. Common congenital heart conditions are:
    • Atrial septal defect: A hole in the heart.
    • Patent ductus arteriosus (PDA): Failure of a particular blood vessel to close normally at the time of birth.

5 Medical Causes of Heart Conditions in Dogs

  1. Heartworms: Heartworms can block heart valves or clog an entire heart chamber.
  2. Over- or under-active thyroid: The thyroid gland can affect your dog’s heart function. Hypothyroidism (under-active thyroid) causes a slower-than-normal heart rate. Hyperthyroidism (over-active thyroid) causes a faster-than-normal heart rate.
  3. Parvovirus: A viral infection that can damage heart muscle and cause acute heart failure in dogs.
  4. Bacterial infection: Bacteria enters the bloodstream and attaches to the heart valves, causing inflammation. A common source of this bacteria is from the gums if the pet has oral disease.
  5. Nutritional deficiency: A lack of vitamin E or Selenium can cause damage to a dog’s heart muscles. Grain free diets from companies that lack feeding trials are a newer concern. The exact mechanism of the disease is still unknown but being studied.

Pet medication logo

Your veterinarian may prescribe a customized, compounded medication. These medications are mixed by trained, licensed compounding pharmacists and often come in dosage forms designed to make giving or applying the medication easier and more accurate.

5 Other Causes of Heart Conditions in Dogs

  1. Age: Dogs’ hearts get weaker as they age, just like humans, which can lead to heart problems.
  2. Injury: Certain injuries, like broken ribs, can damage the heart, forcing it to work harder.
  3. Diet and weight: A high-fat diet, particularly one that includes lots of “people food” and table scraps, causes obesity and makes it more likely that they will develop heart problems.
  4. Exercise: Dogs need exercise, so make sure they get plenty of it. But don’t overdo it. Too much strain on a dog’s heart can cause problems, too.
  5. Breed: All breeds of dog can develop heart disease, but some breeds are more susceptible than others.
    • Middle-aged large and giant breeds more likely to have heart problems are the Great Dane, Rottweiler, German Shepherd, Boxer, Doberman Pinscher, St. Bernard, and Irish Wolfhound.
    • Smaller breeds over or around 5 years of age are at a higher risk.  They are Miniature Poodles, Cocker Spaniels, Pomeranians, Miniature Schnauzers, Dachshunds, Small Terrier Breeds, and Cavalier King Charles Spaniels.

The list of breeds and breed mixes that are more likely to develop heart disease is long. If your dog is not mentioned above, talk to your veterinarian, or visit the American Kennel Club’s website to look up your dog’s breed.

Drug Treatments for Your Dog’s Heart Condition

  • Medication: Cardiac drugs may improve heart function, but they do not cure the underlying disease process. In all likelihood, your pet will remain under treatment for the rest of its life. Daily medications, however, greatly improve the quality of life and life expectancy of dogs with heart disease.
    • o A newer class of heart medications called inodilators has shown great promise. Inodilators like pimobendan help lower the pressure in both the arteries and veins, as well as improve heart muscle strength. This improves blood flow to the body without causing heart muscle damage, which can prolong the symptom-free stage and overall survival of your dog.

    • Digoxin and other drugs like it directly affect cardiac muscle. Digoxin increases cardiac output by improving the heart’s ability to contract. It also decreases blood pressure and pulse rate which helps reduce edema (tissue swelling). Overall, the result is a reduction in heart size, heart rate, blood volume, and pulmonary and venous pressures.

    • ACE Inhibitors like enalapril and benazepril, help reduce blood volume and pressure, relieve stress on the heart, and slow the deterioration of the heart muscles.

    • Spironolactone is often prescribed by veterinarians to treat congestive heart failure and fluid retention.
  • Compounded treatments: Your veterinarian may prescribe a customized, compounded medication. These medications are mixed by trained, licensed compounding pharmacists and often come in dosage forms designed to make giving or applying the medication easier and more accurate. Visit the Wedgewood Pharmacy Medications page for a complete list of compounded medications available.

  • Pacemakers: Pacemakers are most often used for young dogs born with a congenital heart defect. They are not recommended for older dogs because the procedure is too hard on their aging bodies.

5 Tips for Caring for a Dog with Heart Disease

If your dog has been diagnosed by a veterinarian with heart disease, it is important that you as a dog parent be responsible for managing your pet’s cardiovascular health.

  1. Maintain a healthy diet: Work with your veterinarian to determine the best diet. There are prescription diets made specifically for different types of cardiac disease that may benefit your pet.
  2. Avoid high calorie treats: Limit high calorie treats by reading the nutritional information on the label before buying.
  3. No “people food”: Dogs with heart conditions should not eat human food. Our food has too much fat, salt, preservatives, and other bad stuff for your dog to digest properly and is the primary reasons dogs become overweight or obese.
  4. Monitor salt intake: A side effect of heart disease is swollen belly and water in the lungs. A low-salt diet can help manage this symptom better.
  5. Exercise: Exercise helps strengthen the heart. Work with your veterinarian to establish an exercise routine that is not too strenuous for your dog.


Heart disease is common among dogs and some breeds are more likely to develop a heart condition than others. Diagnosing heart disease in its early stages is key to ensuring your pet lives a long, happy life. The earlier you catch it, the sooner you and your veterinarian can treat and maintain the disease and reduce the chance of them developing heart failure.

Frequently Asked Questions

Frequently Asked Questions

Is Canine Heart Disease Curable?

Unfortunately, heart disease cannot be cured. Cardiac medications may improve heart function, but they do not cure the underlying disease process. In all likelihood, your pet will remain under treatment for the rest of its life. Daily medications, however, greatly improve the quality of life and life expectancy of dogs with heart disease.

Is It Possible to Prevent Heart Disease from Affecting Your Dog?

Preventing heart disease from developing in your dog is possible. Be sure to feed your dog a healthy diet, avoid high fat treats, do not give them people food or table scraps, and make sure they get exercise.

Some heart conditions, however, are unavoidable. Congenital heart disease and defects are hereditary, meaning they are passed down by your dog’s parents and you have no control over them. Some dog breeds are more susceptible to heart conditions than others. Knowing if your dog is more likely to develop a condition can help you take measures to catch it and treat it early.

How Is Canine Heart Disease Diagnosed?

The veterinarian will need your dog’s complete medical history along with a complete physical exam to diagnose what type of heart disease your dog has and what stage it is at. An accurate diagnosis will require a series of tests:

  • Blood and Urine Tests: Dogs with heart disease often have problems with their liver and kidneys.
  • Chest X-rays: These reveal the size and shape of the heart, as well as any changes in the lungs like fluid buildup.
  • Electrocardiogram (EKG): Detects abnormalities in the electrical activity of the heart rate and rhythm.
  • Ultrasound (Echocardiogram): Examines the size, shape, and movement of the heart. It can also determine whether the heart is pumping efficiently.
  • Heartworm Antigen Test: Detects abnormal proteins produced by heartworms.
When Should I Seek Urgent Veterinary Care for My Pet Due to Potential Heart Issues?

There are a number of heart diseases and conditions that your dog can have and, fortunately, the signs and symptoms for all of them are similar.

  1. Difficulty breathing
  2. Fast breathing
  3. Restlessness
  4. Persistent coughing or gagging
  5. Weakness
  6. Reduced ability to exercise
  7. Collapsing or fainting
  8. Decreased appetite
  9. Weight loss
  10. Distended or swollen belly

If your pet is experiencing any of these symptoms, contact your veterinarian immediately.

This article is meant to provide general and not medical advice. We strongly recommend that a veterinarian be consulted with for the specific medical needs of your animal.


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