Heart disease in dogs has many causes. Learn more about common heart conditions in dogs.
Heart conditions are seen in more than 10% of dogs, affecting the heart’s structure, function, or electrical activity. Heart disease doesn’t resolve on its own, and it can worsen over time. Early detection of heart disease in dogs can help manage these conditions and help your dog live a happy, healthy life.
Heart conditions in dogs stem from a range of causes, such as age, breed, nutrition, and weight. Some conditions arise later in life, while others are present from birth. Heart diseases can worsen over time and become fatal, which is why early detection and diagnosis are key in managing them. Here’s what dog owners need to know.
Here are some common heart-related terms you may hear from your vet when discussing heart conditions in dogs:
Heart valve disease occurs when a heart valve becomes faulty or diseased. This allows blood to leak back through the valve in the wrong direction, resulting in turbulent blood flow and a characteristic heart murmur. In some cases, this can progress to congestive heart failure.
“A heart murmur is an abnormal heart sound that your vet may hear when listening to your dog's heart with a stethoscope. It sounds like a whooshing or swishing noise caused by turbulent blood flow through the heart. Murmurs can be innocent (for example, some puppies have murmurs that they outgrow) or associated with underlying heart disease of various severity. If your vet hears a heart murmur on your dog, they may recommend additional tests to determine the cause.” - Dr. Liza Cahn
The most common type of heart valve disease is myxomatous mitral valve degeneration (MMVD), which accounts for 80% of canine heart disease. It most commonly affects older dogs and smaller breeds, such as Cavalier King Charles Spaniel, Chihuahua, Miniature Poodle, and more.
Initially, there may be no symptoms associated with heart valve disease, but as the condition progresses, pet parents may notice coughing, exercise intolerance, and difficulty breathing. Certain treatments can help with the symptoms, including diuretics, heart-strengthening medications, blood pressure drugs, heart rhythm stabilizers, and a low-salt diet. The only way to truly fix heart valve disease is with surgery, which some vet cardiologists are able to do. Additionally, pimobendan may help slow the progression.
There are two types of heart muscle disease or myocardial disease. Dilated cardiomyopathy (DCM) occurs when the muscle becomes thin and weak and enlarges the heart, making it harder to pump blood. Large and giant breeds are especially at risk.
In 2018, the FDA began investigating a potential link between grain-free diets and DCM in dogs. Particularly those diets containing a high proportion of peas, lentils, other legumes, and/or potatoes as main ingredients. According to betterpet expert Dr. Erica Irish, “if caught early enough, pre-clinical DCM associated with grain-free diets can resolve if the diet is changed in time.”
Another type, called hypertrophic cardiomyopathy (HCM), occurs when the heart muscles develop too thickly. HCM prevents blood from filling the chambers of the heart, making it difficult for the heart to pump effectively. HCM is most common in certain breeds of cats, such as Maine Coons, but less commonly, it can occur in dogs.
Your vet may choose to treat these conditions with a variety of cardiac medications. However, it’s a very serious disease and needs diagnosis and treatment. If left untreated, heart muscle disease can be fatal.
Heartworm is a preventable disease transmitted through infected mosquitoes. Adult heartworms live in the blood vessels of the lungs and heart. Heartworm can cause significant damage and block blood from flowing from the heart and lungs. Injections of an immiticide and ivermectin oral medication help treat and kill heartworms. It’s critical to use a veterinary-prescribed monthly preventative year-round to prevent heartworm disease.
While heartworm is treatable, it can still cause permanent damage to your dog’s heart and surrounding blood vessels.
Any dog can develop arrhythmia or abnormal heart rhythm. Certain breeds are more prone to arrhythmias, so the cause and treatment vary. Ventricular arrhythmias cause dangerous heart rhythms, often occurring in boxers and bulldogs. Treatment includes monitoring and antiarrhythmic drugs. Large breeds like Great Danes and Dobermans can develop atrial fibrillation, which gets managed with medication.
Other arrhythmias in dogs include heart block, and sick sinus syndrome. These conditions may require a pacemaker or anti-arrhythmics.
Stenosis means narrowing. Two common forms of stenosis exist: pulmonic stenosis and subaortic stenosis.
This form of stenosis is a congenital heart defect that causes the narrowing of the valve between the right ventricle and the pulmonary artery (traveling to the lungs). It’s common in Bulldogs, Boston terriers, Samoyeds, and Labradors.
Subaortic stenosis is common in Boxers, Golden Retrievers, Rottweilers, and German Shepherds. Subaortic symptoms occur due to the narrowing of the aorta, the major blood vessel carrying oxygenated blood from the heart to the body. It’s commonly seen in large breeds and comes in varying degrees, forcing the heart to work harder. It can appear at birth or during the first year of life.
Severity and prognosis can vary widely. In mild cases, no medication is used to treat it. In more severe cases, your vet may recommend medication or surgery.
In pericardial (disease) effusion, an abnormal amount of fluid builds up within the sac around the heart (the pericardium), making it difficult for the heart to beat properly. One of the most common causes is bleeding from a tumor.
Treatment may include pericardiocentesis to remove the fluid, however, it’s important to address the underlying cause. Because this condition can reoccur, a specialist may recommend removing the pericardium, which may improve the quality of life.
Heart disease can lead to congestive heart failure (CHF). CHF occurs when the heart fails to pump enough blood needed throughout the body. Fluid can build up in the lungs, abdomen, or other tissues. The most common symptoms of CHF include coughing, increased respiratory rate and effort, exercise intolerance, weight loss, and swollen abdomen.
With congestive heart failure, some dogs may have increased thirst or urination. CHF is a serious and progressive condition, but it can be managed with medications like diuretics, vasodilators, and inotropic medications. The prognosis will depend on the underlying cause and response to treatment.
Decoding your dog’s symptoms can be challenging, especially since many of them overlap. With early heart disease, there may not be any symptoms, and sometimes, sudden death is the only symptom. However, early detection is key to heart disease. Routine vet visits can aid your vet in detecting heart disease early on.
Your vet may recognize certain symptoms pet owners may not immediately notice and perform diagnostic testing if they suspect a heart condition. Depending on the type of heart disease, dogs often experience a combination of symptoms.
Persistent or unusual coughing for more than a couple of weeks could indicate heart disease. Fluid may back up into the lungs, causing your dog to cough. An enlarged heart can also put pressure on the trachea, leading to a persistent cough.
Dogs may faint or lose consciousness due to a lack of blood flow and oxygen to the brain, a condition known as syncope. While causes of fainting or collapse vary, if this happens, immediately take them to the vet.
Fluid buildup can lead to breathing difficulties. You may notice labored breathing, distress, and a desire not to lie down. They may stand with their mouth open and visually appear to have difficulty breathing. This can also contribute to appetite loss as it’s harder to bend down and eat while having trouble breathing.
An unwillingness to exercise or excessively panting or breathing hard after non-vigorous play can all signal heart disease. Not wanting to play, acting lethargic, or taking a long time to recover can also be indicators.
Behavioral changes in your dog can also indicate they aren’t feeling well. They may hide, look visibly distressed, or act odd.
Abdominal swelling can occur with parasites, bloat, an obstruction, or a tumor. However, this can also be a symptom of heart disease due to fluid build-up.
Their gums may appear pale or have a blue/gray tinge. This coloring is due to a lack of oxygen due to insufficient blood flow and circulation.
High levels of cardiac hormone-like substances, decreased appetite, and metabolic demands can cause your dog to lose weight. This condition, known as cardiac cachexia, results in loss of muscle and body weight.
Loss of appetite
Not eating or refusing their favorite treats is a sure sign your dog is not feeling well. Fluid accumulation in the abdomen can make your dog feel less hungry and may indicate heart disease. Additionally, certain medications may cause GI upset.
Fluid buildup in the heart and lungs can cause difficulty sleeping in your dog. You may also notice difficulty breathing or coughing and restlessness at night.
Heart conditions in dogs can be hereditary or acquired. There is no one cause of heart disease, and a variety of factors can play a role. Aside from being born with a heart defect, age, breed, weight, and nutrition can exacerbate such conditions.
Hereditary heart disease passes from parent to child. These are genetic conditions that can either be present at birth or go undetected until later in life. Additionally, certain factors like obesity can heighten the risk of hereditary conditions.
Congenital heart disease differs from hereditary in that it arises during development in the womb. Because of how they develop, they are not passed from parent to child and are not inherited. Genetic defects, infection, poisoning, medication, environmental conditions, and poor nutrition during pregnancy can lead to congenital heart diseases.
Acquired heart diseases develop later in life. Symptoms of acquired heart disease may not be obvious until a dog is an adult or older. Certain breeds and genetics can play a role in your dog’s development of heart disease later in life. Overweight dogs and improper nutrition may also result in a higher risk of developing severe symptoms.
A veterinarian will physically examine your dog and listen to their heart and lungs to detect abnormal rhythms, murmurs, or signs of fluid in the lungs. They’ll also check their pulse and for any fluid build-up in their abdomen.
During a physical examination, your vet will also ask about their history, symptoms, and behavior and may perform further testing to evaluate your dog’s heart health. Sometimes, your vet may recommend a veterinary cardiologist if they suspect an irregular heart rhythm or heart murmur.
Your vet may also want to run bloodwork and perform other diagnostic tests. Treatment for heart conditions depends on the diagnosis and whether or not the condition is manageable.
Preventing heart disease in dogs is not always foolproof. Even with the best care and preventative steps, some dogs will still develop heart issues. However, there are several steps you can take to reduce the risk:
Choosing a breeder who tests their dogs for genetic heart conditions can lower the risk of heart disease in puppies. Testing can help avoid passing on these conditions and minimize the risk of abnormalities in litters.
Some dog breeds are more susceptible to heart disease due to their genetic makeup. Choosing breeds with a lower risk of heart issues can reduce the chances of them developing a heart condition. Certain susceptible breeds include Cavalier King Charles Spaniels, Dachshunds, Miniature Poodles, Dobermans, Boxers, Golden Retrievers, and Miniature Schnauzers.
Heartworm disease can cause serious heart problems and is preventable. Using a heartworm preventative protects them from heartworms infecting their blood vessels, heart, and lungs.
A balanced diet is essential for your dog’s heart health. Feeding them high-quality food ensures they get the optimal nutrients to support your dog’s cardiovascular system. Table scraps, excess treats, grain-free, and raw food diets can lead to nutritional imbalances.
Maintaining a healthy weight helps reduce stress on their heart. The more body weight your dog has, the more resistance their heart has to overcome to pump and circulate blood.
A physical exam is the first step in diagnosing early-stage heart disease in dogs. A vet checks the lungs and heart during a physical exam to listen for abnormal sounds. Your vet may also recommend bloodwork and imaging to help evaluate your dog’s heart.
Valvular disease and dilated cardiomyopathy are common heart conditions in dogs.
This can vary significantly depending on the underlying cause and severity of the disease. Generally, after CHF develops, a dog can live anywhere from six months up to two years with appropriate treatments.
Physical symptoms of a dog with a heart condition include lack of energy, fainting, collapse, coughing, breathing difficulties, weight loss, or a swollen stomach.
In simplified terms, Stage A means a dog is predisposed to heart disease, but their heart shows no changes. Stage B, a heart murmur is present. Stage C symptoms or signs of congestive heart failure are present. Stage D, the dog does not respond to treatment.
