Heart conditions in dogs are seen in more than 10%, 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 (Trusted Source) (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. Treatments for heart valve disease include diuretics, heart-strengthening medications, blood pressure drugs, heart rhythm stabilizers, and a low-salt diet.
There are two types of heart muscle disease or myocardial disease. Dilated cardiomyopathy (DCM) (Trusted Source) 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 (Trusted Source) . Particularly those diets containing a high proportion of peas, lentils, other legumes, and/or potatoes as main ingredients.
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.
Any dog can develop arrhythmia or abnormal heart rhythm (Trusted Source) . 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, myocarditis, and sick sinus syndrome. These conditions may require a pacemaker or anti-inflammatory treatments.
Stenosis means narrowing. Two common forms of stenosis exist: pulmonic stenosis (Trusted Source) and subaortic stenosis. Pulmonic 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 (Trusted Source) 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, (Trusted Source) 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). (Trusted Source) 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.
Heart conditions in dogs can be hereditary, congenital, 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:
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.
