Ten percent of dogs in the United States have heart disease. The two most common causes of canine heart disease are valve disease and contractility issues. While both of these conditions can lead to congestive heart failure, early detection and treatment can help prolong and improve the quality of your dog's life. The symptoms of heart disease in dogs, such as fatigue or exercise intolerance, may be subtle and are often passed off as normal signs of aging, so learning what to look for is important.
What is heart disease in dogs?
Any disease that affects the heart is heart disease; however, there are two common types. One is when a valve (or valves) isn't functioning correctly. This is called valvular insufficiency, or mitral valve disease. The other type is when heart muscle degenerates and becomes too thin. Valves are doorways located between the top (atrium) and bottom (ventricle) chambers of the heart as well as where blood comes into and out of the heart. Like humans, dogs have four heart valves.
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Dogs can also develop heart disease for a variety of other reasons, such as nutrition (for example, grain-free diets that may result in low taurine levels); aging; obesity; genetics; or congenital defects, such as birth defects, tumors, and heartworm disease.
Types of heart disease in dogs
Though there are multiple causes of heart disease, such as genetics, congenital defects, aging, and nutrition, the majority of cases are caused by valve disease and heart muscle disease.
- Valve disease: Of the top two causes, this is the most prevalent, particularly in the mitral valve of small-breed dogs. Valve disease is when the leaflets of a valve don't close properly. This affects blood flow throughout the entire body. Valvular disease will cause a turbulent sound, called a murmur, that your veterinarian will likely be able to hear with a stethoscope. Murmurs are graded from I to VI, with Grade I being difficult to hear with a stethoscope even in a quiet room. With Grade VI, the murmur is so loud that it can be heard without the stethoscope fully touching a dog's chest.
- Heart muscle disease: The most common form of heart muscle disease is dilated cardiomyopathy, or DCM. With DCM, the heart wall muscle degenerates and becomes thin. The thinned-out muscle's ability to pump blood is compromised, which eventually leads to congestive heart failure (CHF).
Symptoms of heart disease in dogs
There are several common symptoms of heart disease in dogs. They are as follows.
Murmurs and Arrhythmias
Heart murmurs are an extra or unusual sound heard by your veterinarian when they listen to your dog's heart. Murmurs can be a sign of heart valve problems. Arrhythmias are irregular heartbeats due to faulty electrical signaling. Like murmurs, they can interfere with the effective pumping of blood by the heart. A dog may also have an increased or decreased heart rate with an arrythmia.
Respiratory symptoms of a heart condition may include difficulty breathing, coughing, and wheezing. You may notice that these symptoms increase after exercise or during strenuous activity. In dogs with more advanced heart disease, even something like a toenail trim where the pet resists and struggles can cause respiratory distress.
Breathing difficulty may disrupt your dog's normal sleeping patterns, resulting in increased fatigue. Decreased oxygenation can also cause a pet to have a blue tinge to their gums.
Some changes in behavior may indicate a heart condition as well. Your once active and affectionate dog may seem reluctant to exercise, play, or even go out for a short walk. They may pass on a cuddling session with you and prefer to be alone. Your dog may isolate themself from other animals and humans, appearing depressed. It's also possible that a heart condition can cause a pet to collapse due to low oxygen levels in their blood.
While your dog used to eat up their bowl of food, you may notice that they now have a loss of appetite. They may refuse treats and bones. At some point, they may experience extreme weight loss. You may also notice abdominal swelling. A swollen belly can occur due to increased pressure in the veins that drains into the abdominal cavity. This increases fluid retention in the abdomen.
Diagnosing heart disease in dogs
The first step in diagnosing heart disease is a physical exam. Dogs with symptoms and physical exam findings that suggest heart disease, such as a murmur heard with a stethoscope, will need some or all of the following tests. Some can be performed by your veterinarian, but in some cases, you may be referred to a veterinary cardiologist.
- Chest X-rays (radiographs): This can show heart enlargement as well as changes in the lungs (like fluid buildup) and changes in blood vessels that can accompany heart disease.
- Blood pressure: A systolic blood pressure that's consistently elevated is common with heart disease. This is a simple test that can be performed by your veterinarian.
- Blood tests: These tests may include a heartworm test and potentially a cardiac health test called NT-proBNP. This second test helps veterinarians evaluate if heart muscle cells are being overly stretched and stressed.
- Echocardiogram: A heart ultrasound is used to evaluate the heart valves, blood flow through the heart, and the muscle thickness of the sides of the heart.
- Electrocardiogram (ECG): This test evaluates the heart's rhythm and determines if there are arrhythmias.
Are some dogs more at risk for heart disease?
Yes, some dogs are more at risk for heart disease. But because many of the signs of heart disease can also be seen with normal aging in any dog breed, it is important to check with your veterinarian to rule out heart issues. Specific breeds are predisposed to heart conditions and require closer monitoring.
Higher risks for heart valve disease appear in:
- Cavalier King Charles spaniels
- Boston terriers
- Fox terriers
- Miniature pinschers
Heart muscle disease is more common in:
- Doberman pinschers
- Great Danes
- Afghan hounds
- Cocker spaniels
- Irish wolfhounds
- Saint Bernards
- Scottish deerhounds
Pet parents with older dogs and breeds more prone to heart disease, such as Chihuahuas, should watch for common symptoms of heart disease. These are coughing, shortness of breath, tiring more easily, and changes in appetite. If you think your pet has a heart condition, take them to your veterinarian right away for an exam and testing. Part of a physical exam includes evaluating your pet's heart health by listening to their chest with a stethoscope. If your dog is diagnosed with heart disease, your veterinarian will develop a treatment plan. This can involve medications like diuretics, supplements, regular checkups, and a special diet that supports heart function.