“Heart disease” is not one diagnosis. It describes several conditions affecting a dog’s heart, and the cause matters because testing and treatment differ. Some dogs have a murmur for years without clinical heart failure. Others develop reduced pumping ability or abnormal rhythms that need closer monitoring.
Common types of canine heart disease
Degenerative mitral valve disease
In many older, smaller-breed dogs, the mitral valve gradually becomes leaky. A veterinarian may hear a murmur, but an examination and sometimes imaging are needed to determine whether the heart is enlarged or fluid congestion is present. A murmur by itself does not prove heart failure.
Dilated cardiomyopathy
This disease affects the heart muscle and its ability to pump blood. It is seen in some larger breeds and can lead to weakness, arrhythmias or heart failure. Genetics may play a role in predisposed breeds, but other causes are possible. An echocardiogram is often central to diagnosis.
Congenital abnormalities and rhythm disorders
Some dogs are born with structural heart defects. Other dogs develop electrical rhythm disturbances, sometimes without a murmur. The best testing depends on what the veterinarian finds during an examination.
Heartworm-related injury
Heartworms are transmitted by mosquitoes and can damage the blood vessels and cardiopulmonary system. Veterinary-recommended prevention and routine testing are important; a heartworm infection requires specific medical management, not ordinary home heart medications.
What does age or breed tell you?
Age, family history and breed can change risk, but none confirms a diagnosis. Small breeds may be predisposed to mitral valve disease, while some large breeds are at increased risk for cardiomyopathy. A veterinarian may recommend a heart examination or an echocardiogram for a dog with concerning findings or breed history.
Signs worth discussing with your vet
- Reduced interest in walks or tiring sooner than usual
- A persistent cough, especially with changes in breathing
- Fainting, weakness or episodes of collapse
- A swollen abdomen or unexplained weight or appetite changes
- Faster or more difficult breathing while resting
These signs have many possible causes. Coughing is not proof of heart disease, and some dogs with heart disease do not cough. Learn more in our guide to canine heart-disease symptoms.
Which tests might the veterinarian use?
After listening to the heart and lungs, a veterinarian may recommend chest X-rays, an echocardiogram, an electrocardiogram, blood pressure measurement or laboratory work. A cardiology consultation may be useful for complex or advanced disease. Test selection should answer a specific clinical question rather than follow a fixed checklist.
When to seek emergency help
Labored breathing, blue or very pale gums, collapse or unresponsiveness are emergencies. Seek in-person veterinary care immediately. An online appointment should not delay transport. A new cough, reduced stamina or a new murmur deserves a veterinary appointment even when your dog otherwise seems comfortable.
Can heart disease be prevented?
Not every heart condition can be prevented. Work with your veterinary team on heartworm prevention, a balanced diet, appropriate exercise and checkups. Avoid giving heart supplements or changing a diet to “treat” a suspected heart problem without discussing the diagnosis and nutritional needs with your veterinarian.
Further reading: ACVIM consensus guidance for degenerative mitral valve disease; Merck Veterinary Manual: when to seek veterinary help.
General educational guidance, not a veterinary diagnosis. No individual veterinarian review is represented.
This article is for general education and is not a substitute for care from your own veterinarian. Learn about The Pet Vet and our editorial policy.