Heart Disease in Dogs: Symptoms, Causes, and Treatment

Heart disease in dogs is any condition that affects the heart’s ability to pump blood effectively, including valve disease, heart muscle disorders, arrhythmias, and heartworm infection. Early signs may be subtle—such as coughing, fatigue, or decreased stamina—but the condition can progress to breathing difficulty or congestive heart failure if left untreated.

Prompt diagnosis and ongoing management with medication, diet changes, or, in some cases, surgery can significantly improve a dog’s quality of life. Here’s what pet parents need to know about symptoms, causes, treatment, and prevention.

What Is Heart Disease in Dogs?

Heart disease in dogs refers to any abnormality within the heart that reduces its ability to pump blood efficiently.  

Dog heart disease symptoms are initially mild but can quickly progress if the condition is not managed.  

Dog heart condition symptoms may include trouble breathing, coughing, and lethargy. Prompt diagnosis and treatment is essential in slowing disease progression and preserving a dog’s quality of life.  

Most Common Types of Heart Disease in Dogs

Let’s look at the most common types of heart disease in dogs: 

• Heart valve disease: The heart has four valves that keep blood moving in the right direction. When a dog is born with a faulty valve or a valve becomes diseased or damaged, blood flow through the heart becomes turbulent (less smooth). This causes a heart murmur and can eventually lead to congestive heart failure as blood flow becomes less efficient. Myxomatous mitral valve degeneration (MMVD) is the most common type of heart valve disease in dogs, and tends to affect older, small-breed dogs. 

• Myocardial (heart muscle) disease: The heart is made mostly of muscle. If that muscle degenerates and thins, the heart becomes less able to pump blood. This is called dilated cardiomyopathy, or DCM. Hypertrophic cardiomyopathy or HCM, is another type of heart disease that develops when the heart muscle becomes too thick, preventing normal amounts of blood from filling the heart chamber. 

• Heartworm disease: Heartworms are spread through the bites of infected mosquitos. Adult heartworms live in the lung’s larger blood vessels and in a dog’s heart. They cause a lot of inflammation and damage and can block the flow of blood from the heart into the lungs. 

• Arrhythmias: A heart rhythm that is too slow, too fast, or irregular can make it hard for the heart to pump blood to the lungs and rest of the body. 

• Shunts: Shunts are abnormal vessels or holes in and around the heart that prevent blood from circulating normally. Most cardiac shunts in dogs—such as patent ductus arteriosus and ventricular septal defect—are congenital (present at birth). 

• Stenosis: Puppies can be born with a narrowed area around their heart valves, making it hard for blood to pass through. Pulmonic stenosis and subaortic stenosis are the most common forms in dogs. 

• Pericardial disease: The pericardium is the sac that surrounds the heart. The heart can’t beat effectively if the pericardium becomes stiff or if the area between the pericardium and the heart fills with fluid (usually blood) or air. 

• Congestive heart failure, or CHF: A consequence of many types of heart disease, congestive heart failure develops when the heart can no longer pump blood well enough to meet the needs of the body. Fluid may leak out of blood vessels and collect in or around the lungs, in the abdomen, or within other tissues. 

Symptoms of Heart Disease in Dogs

Common symptoms of heart disease in dogs include: 

• Coughing 

• Difficulty breathing 

• Becoming tired easily 

• Weakness 

• Weight loss 

• Diarrhea 

• Blue-tinged or gray gums (cyanosis) 

• Abnormal swellings (such as of the legs or belly) 

• Difficulty sleeping 

• Fainting 

• Collapse 

These signs can also be caused by other types of health problems, such as diseases affecting the lungs, so it’s important to get your dog to the veterinarian for an accurate diagnosis immediately.  

Causes of Heart Disease in Dogs

There are various causes for heart disease in dogs, which include the following: 

• Age-related changes 

• Poor nutrition, such as taurine deficiency 

• Heartworm infection 

• Congenital defects, such as patent ductus arteriosus  

• Obesity 

• Chronic high blood pressure 

• Infections, such as parvovirus  

• Heart tumors 

• Severe periodontal disease (as bacteria from the mouth travels to the heart valves) 

How Veterinarians Diagnose Heart Disease in Dogs

The first step in diagnosing heart disease in dogs is a complete physical examination. Be prepared to answer questions about your dog’s health history and the symptoms you have been seeing at home.  

A veterinary cardiologist may also be consulted. 

Diagnostic testing for heart disease is usually needed. This may include: 

• Chest X-rays to look at the heart’s shape and size and to evaluate the lungs and other structures in the chest 

• Electrocardiogram (ECG) to identify heart rhythm abnormalities 

• Echocardiogram (an ultrasound exam) to watch how blood flows through the heart and to evaluate heart valves and muscle 

• Heartworm tests 

• Blood pressure measurement 

• Blood work 

Treatment of Heart Disease in Dogs

Several treatments are available for heart disease in dogs. Whenever possible, treatment is directed at the underlying cause. Sometimes a heart disease can be cured, and a dog’s symptoms may disappear. For example: 

• Adult heartworms can be eliminated with injections of melarsomine, a derivative of arsenic. 

• Some types of arrhythmias can be managed with a pacemaker or with surgical interventions. 

• Surgery may also be an option to correct a cardiac shunt, stenosis, or some types of valvular or pericardial disease. 

More commonly, heart disease in dogs is managed with medications that can: 

• Help the heart to pump more efficiently (enalapril and pimobendan, for example) 

• Aid in the elimination of excess fluid from the body (furosemide or spironolactone, for example) 

• Normalize heart rhythm (atenolol, sotalol, propranolol, amiodarone, diltiazem, and digoxin, for example) 

Your veterinarian may also recommend modifying your dog’s diet.  

Weight loss or nutritional supplements (taurine, for example) can help some dogs with heart disease. 

Feeding a diet that is low in salt may help reduce fluid retention if a dog has congestive heart failure.  

Your veterinarian may recommend a prescription diet like Hill's® Prescription Diet h/d Heart Care or Purina® Pro Plan Veterinary Diets CC Cardiocare.  

Many dogs who developed dilated cardiomyopathy while eating a boutique diet have returned to normal after being switched to more traditional dog foods. 

Prognosis of Heart Disease in Dogs

When heart disease in dogs is caught early and treated appropriately, pups often live happily for many more years. 

However, severe cases of heart disease or those that have progressed to congestive heart failure bring with them a more guarded prognosis.  

There usually comes a time when available treatment options can no longer maintain a dog’s quality of life, and humane euthanasia may be recommended.  

How To Prevent Heart Disease in Dogs

To prevent heart disease in dogs, pet parents can take the following steps: 

• Ensure your dog receives regular wellness exams and blood work. 

• Keep your dog up to date on routine vaccinations. 

• Feed your dog a high-quality, commercially available diet and maintain an optimal weight. 

• Ensure your dog stays up to date on heartworm prevention. 

• Brush your dog’s teeth and do professional dental cleanings to promote oral hygiene.