Heart Disease in Dogs

Causes, Treatment, and Prevention

Mixed breed dog at a vet's office
Heart disease can occur in any dog breed but some are at a higher risk of developing it.

Monty Rakusen/ Getty Images 

Heart disease is a multifaceted condition that can affect any dog, but older dogs are more vulnerable. Symptoms can be vague and seemingly unrelated to the heart, ranging from coughing and fatigue to abdominal distension. Untreated, heart disease will progress and likely prove fatal. Knowing the warning signs and treatment options for your dog's particular heart problem can help you keep your dog's heart going strong for as long as possible.

What Is Heart Disease?

Heart disease refers to any type of disease that affects the heart. The heart is an incredibly vital organ, and if it is unable to function properly, multiple parts of the body will suffer. About 10% of all dogs examined by a veterinarian are found to have some type of heart disease and they often go undetected by their owners unless the disease is severe.

Symptoms of Heart Disease in Dogs

Heart disease is often difficult to recognize since the heart is an internal organ and its malfunction causes vague symptoms. Once the problem becomes more severe, though, owners may begin to notice the following indications of illness:


  • Coughing
  • Shortness of breath
  • Fatigue
  • Collapse
  • Distended abdomen
  • Pale or blue gums

Since the heart is responsible for pumping oxygenated blood throughout the body, breathing issues will often be the first sign of heart disease in dogs. Coughing, fatigue, and shortness of breath are the most common signs, but if the disease worsens, then pale or blue gums and even collapse will occur as a result of low oxygen.

Some dogs with advanced heart disease will accumulate fluid in their abdomen as a result of blood leaking from vessels and pooling in the body cavity. This accumulation is a condition called ascites and is a particularly serious symptom that should be evaluated by a veterinarian as soon as possible.

Causes of Heart Disease

Heart disease often develops later in a dog's life, but certain heart problems can be present from birth. Heart disease that develops over time is a result of one or several of the following causes:

  • Heartworm infection from mosquitoes
  • Genetics
  • Bacterial, viral, or protozoal infection
  • Nutrient deficiencies (carnitine and taurine specifically affect heart health)
  • Toxins
  • Various medications
  • Tumors

Dogs that have congenital heart disease can develop it in utero from one or more of the following causes:

  • Genetics
  • Medications taken by the pregnant mother
  • Environmental factors
  • Infection
  • Poisoning
  • Poor nutrition

Diagnosing Heart Disease in Dogs

Since heart disease can easily go unnoticed, early stages may only be detected by your veterinarian. A full physical examination will be performed and your dog's breed, history, and any symptoms you are seeing or hearing at home will be taken into consideration.

A stethoscope will be used to listen to your dog's heart and determine if a murmur or abnormal rhythm is present. If heart disease is suspected, chest x-rays, blood tests (including a heartworm test), and an echocardiogram (ECG)may be recommended.


Once heart disease is diagnosed, a treatment plan specific to the type of heart disease your dog has will be discussed. Heartworm disease is a curable form of heart disease, but it requires strong medications to kill the heartworms inside your dog. The treatment program is lengthy and can be very taxing for a dog.

Aside from tumors, which may be surgically removed, most types of heart disease usually require life-long monitoring and medications.

Prognosis for Dogs with Heart Disease

The prognosis largely depends on the type and severity of heart disease in a dog. Heartworms can be eradicated, but dogs occasionally die during treatment. Tumors, especially if they are cancerous, are life-threatening and carry a guarded prognosis based on the severity and spread of the growth.

That said, many dogs with heart disease can be successfully managed with medication for months or years.

How to Prevent Heart Disease in Dogs

The most preventable form of heart disease is heartworm infection. In regions where winters are mild or heartworm cases appear throughout the winter months, heartworm prevention should be administered year-round to prevent heartworm transmission from mosquitoes.

While guaranteed prevention is impossible, you may be able to help lessen the chances of your dog developing heart disease during the course of its life by feeding a nutritious diet, giving daily exercise opportunities, and making sure your dog stays at a healthy weight.

If you are concerned about specific nutritional deficiencies that are known to contribute to heart disease, such as carnitine and taurine, discuss with your vet which diet may be best for your dog.

Medications with known side effects on the heart should not be administered without the need for them and avoiding exposure to toxins and contaminated areas should always be a priority for optimal health.

Types of Heart Disease in Dogs

Common diseases of the heart include:

  • Valvular Disease: Mitral valve issues are the most common type of valvular heart disease in dogs but tricuspid valve disease can also be seen. Valves are little flaps of tissue that act as doors between the chambers of the heart. These valves prevent blood from flowing backward through the heart but when they do not work as they should, blood does not flow properly through the body.
  • Arrhythmogenic Right Ventricular Cardiomyopathy: Also referred to as Boxer cardiomyopathy due to the nearly exclusive occurrence in the boxer breed, this is heart disease that causes an irregular heartbeat. The heart beats abnormally fast and blood is unable to be pumped throughout the body due to a change in the muscle in the right ventricle of the heart.
  • Heartworm Disease: Heartworms are passed through mosquitoes. When a mosquito bites a dog, the heartworm larvae enter the dog's bloodstream. They grow and develop into worms that eventually fill the lungs and heart of a dog if a dog is not on preventative heartworm medication.
  • Dilated Cardiomyopathy (DCM): The heart is responsible for pumping blood through the body but in dogs with DCM, the heart has lost its ability to do this job effectively. DCM is very common in dogs and may go undetected for some time.
  • Myocarditis: If a dog has myocarditis, the heart has become inflamed and muscle cells are dying off.
  • Congenital Abnormalities: Some dogs are born with abnormalities or defects in their hearts that do not allow them to work properly. Examples of congenital heart disease include patent ductus arteriosus (shunt), pulmonic stenosis, aortic stenosis, persistent right aortic arch, and ventricular septal defect.

Congestive heart failure (CHF) is not a disease itself but rather the result of heart disease. Heart failure occurs when blood is no longer able to be adequately pumped throughout the body by the heart. Since some heart diseases are not able to be cured, they will eventually progress to heart failure.

If you suspect your pet is sick, call your vet immediately. For health-related questions, always consult your veterinarian, as they have examined your pet, know the pet's health history, and can make the best recommendations for your pet.