Understanding Canine Heart Issues: A Guide by Veterinarian Catherine Barnette, Published on March 11, 2025
Common Causes and Symptoms of Heart Disease in Dogs
Heart disease, or cardiac disease, is a significant concern for many dog owners. Approximately 10% of dogs seen by primary care veterinarians have some form of heart disease, with the most common causes being degenerative mitral valve disease (DMVD), dilated cardiomyopathy (DCM), congenital heart defects, myxomatous degeneration of heart valves, heartworm disease, arrhythmias, and hypertrophic cardiomyopathy.
Degenerative Mitral Valve Disease (DMVD)
This is the most frequent heart condition, especially in small breed dogs like Cavalier King Charles Spaniels. It involves thickening and degeneration of the mitral valve, causing it to leak and impair blood flow. This valve leakage can cause murmurs and lead to heart failure if untreated.
Dilated Cardiomyopathy (DCM)
More common in large breeds such as Dobermans and Boxers, DCM is characterized by an enlarged and weakened heart muscle. This reduces the heart’s pumping efficiency and can cause heart failure. Nutritional deficiencies, such as taurine deficiency in dogs on certain diets (home-cooked, vegetarian, vegan), can contribute to DCM.
Congenital Heart Defects
These are structural heart problems present from birth and can be inherited. Examples include pulmonary valve stenosis and ventricular septal defects. These affect the normal flow of blood through the heart and can cause murmurs and cardiac complications.
Myxomatous Degeneration of Heart Valves
This condition causes thickened, stiff heart valves (commonly mitral valve) that leak. It is prevalent in older dogs and leads to abnormal blood flow, heart murmurs, and potential heart failure.
Heartworm Disease
Caused by parasitic infection, heartworms reside in the heart and pulmonary arteries, damaging heart function and blood flow. This is a treatable but serious cause of heart disease.
Arrhythmias and Hypertrophic Cardiomyopathy
Abnormal heart rhythms and thickened heart muscles, respectively, can also cause murmurs and heart dysfunction in dogs.
In its early stages, heart disease is often asymptomatic or nearly asymptomatic. However, as the disease progresses, signs at home may include coughing, increased respiratory rate, exercise intolerance, fainting, shortness of breath, difficulty breathing, a productive cough, a blue tinge to gums, swollen belly due to fluid accumulation, weak pulse, and lethargy. Congestive Heart Failure (CHF) is a late-stage effect of any form of canine heart disease, and is treated with diuretics such as furosemide to remove extra fluid from the body and the lungs, and often paired with Vetmedin and ACE inhibitors for cases of CHF caused by MVD or DCM.
Early veterinary diagnosis through physical exams, heart auscultation, and diagnostic imaging (echocardiograms, ECG) is crucial for managing these conditions. If a dog is showing signs of heart disease, schedule an appointment with a veterinarian.
It's also important to note that feeding an imbalanced diet can increase a dog's risk of heart disease. Discuss diet with your veterinarian and ensure that you are feeding a nutritionally complete and balanced diet appropriate for your dog's life stage.
Some breeds are more likely to develop heart disease than others, such as Cavalier King Charles Spaniels, Miniature Schnauzers, Toy Poodles, Chihuahuas, Shih Tzus, Boxers, and Doberman Pinschers. If you are considering a purebred dog, consult the Orthopedic Foundation for Animals' recommended list of breed-specific screenings to determine whether cardiac screenings are recommended for that breed.
In conclusion, heart disease in dogs can be a silent but potentially life-threatening condition. Regular veterinary check-ups, a balanced diet, and preventative measures such as year-round heartworm preventative can help ensure your dog's heart health.
- Science has shown that heart disease is a significant concern in the workplace-wellness of dogs, affecting approximately 10% of dogs seen by primary care veterinarians.
- Degenerative mitral valve disease (DMVD) is the most frequent heart condition, particularly in small breed dogs like Cavalier King Charles Spaniels, where it causes impaired blood flow due to the thickening and degeneration of the mitral valve.
- Dilated cardiomyopathy (DCM) is more common in large breeds such as Dobermans and Boxers, characterized by an enlarged and weakened heart muscle, which reduces the heart’s pumping efficiency and can cause heart failure.
- Congenital heart defects, present from birth and often inherited, can affect the normal flow of blood through the heart and include conditions like pulmonary valve stenosis and ventricular septal defects.
- Myxomatous degeneration of heart valves, prevalent in older dogs, causes thickened, stiff heart valves that leak, leading to abnormal blood flow, heart murmurs, and potential heart failure.
- Heartworm disease, caused by parasitic infection, resides in the heart and pulmonary arteries, damaging heart function and blood flow, making it a treatable but serious cause of heart disease.
- Arrhythmias and hypertrophic cardiomyopathy can also cause heart dysfunction, with abnormal heart rhythms and thickened heart muscles, respectively.
- In its early stages, heart disease is often asymptomatic or nearly asymptomatic, but as the disease progresses, signs may include coughing, increased respiratory rate, exercise intolerance, and lethargy, among others.
- Congestive Heart Failure (CHF) is a late-stage effect of any form of canine heart disease, and is treated with diuretics, Vetmedin, ACE inhibitors, and other medications.
- Regular veterinary check-ups, balanced nutrition, and preventative measures such as year-round heartworm preventative can help ensure a dog's heart health.
- Purebred dogs like Cavalier King Charles Spaniels, Miniature Schnauzers, Toy Poodles, Chihuahuas, Shih Tzus, Boxers, and Doberman Pinschers are more likely to develop heart disease.
- Consulting the Orthopedic Foundation for Animals' recommended list of breed-specific screenings can help determine whether cardiac screenings are recommended for a specific breed.
- Mental health, skin care, fitness, and exercise play an essential role in a dog's overall health and wellness, and should not be overlooked when considering a dog's heart health.
- Therapies, treatments, and medications such as cbd, antibiotics for skin conditions, and specialized diets for chronic diseases, can supplement veterinary care in managing canine heart disease, while proper parenting and weight management are vital for a dog's cardiovascular health.
