Heart Disease in Dogs

What Is Heart Disease in Dogs?

Lots of dogs get heart disease, particularly as they get older. The heart’s primary responsibility is to pump blood throughout the body, and when something goes wrong with such a vital organ the consequences can be serious.

Learning about the common types of heart disease in dogs can help you identify when a problem might be brewing. Dogs with signs of heart disease need to be seen by a veterinarian so they can get the care they need early on when options can work best, and they may need long-term evaluations by a veterinary cardiologist.

Most Common Heart Diseases in Dogs

Here are some of 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

Different types of heart disease can lead to different symptoms, but most dogs have some combination of the following signs of heart disease:

• Coughing

• Difficulty breathing

• Becoming tired easily

• Weakness

• Weight loss

• Diarrhea

• Blue-tinged or gray gums

• Abnormal swellings (legs or belly, for example)

• 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 as soon as possible.

Causes of Heart Disease in Dogs

Heart disease in dogs is either congenital (present at birth) or acquired (occurs later in life). Symptoms of congenital heart disease usually develop in puppies or young adult dogs, and often genetics plays a big role in determining which dogs are affected.

Signs of acquired heart disease may not be obvious until a dog is middle-aged or older, even though genetics and a dog’s breed are still important determinative factors. Dogs that are overweight may be at higher risk for developing more severe symptoms of heart disease.

Nutrition plays a role in some forms of heart disease. For example, dogs that are fed diets deficient in the amino acid taurine are at an increased risk of developing dilated cardiomyopathy. Some breeds, such as Golden Retrievers, appear to have a higher requirement for taurine in their diet.

Recently, a form of dilated cardiomyopathy has been associated with certain types of dog food (boutique, exotic, and grain-free), but taurine deficiency doesn’t appear to be to blame and a cause has not been identified.

How Veterinarians Diagnose Heart Disease in Dogs

The first step in diagnosing heart disease in dogs is a complete physical examination. The veterinarian will use a stethoscope to listen to your dog’s heart and lungs to check for abnormal rhythms and sounds like heart murmurs or crackles (evidence of fluid in the lungs).

Your vet will also feel your dog’s pulse and check for fluid buildup in the abdomen and other tissues. 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

Other lab work and diagnostic testing may be necessary, based on the specifics of the dog’s case.

Treatment of Heart Disease in Dogs

Many 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.

Recovery and Management of Heart Disease in Dogs

When heart disease is caught early and treated appropriately, dogs 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.