Heart Disease in Dogs: A Comprehensive Guide

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It might surprise you, but did you know that dogs can have heart problems? Just like people, dogs can suffer from many of the same ailments, including heart disease (otherwise known as cardiomyopathy).

Current estimations place the number of dogs suffering from heart disease at around 7.8 million, or roughly 10% of all dogs in the US. That percentage only grows as dogs age. It’s thought that over 75% of dogs in their golden years suffer from some kind of heart disease. Despite such large numbers, there are many humans unaware that their canine family members could be at risk for such a thing as heart disease.

Causes of Heart Disease in Dogs

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There are two categories for heart disease that dogs can fall under. One is acquired heart disease and the other (though less common) is congenital heart disease. Congenital heart disease tends to be diagnosed when a dog is very young and only about 5% of all heart disease cases in dogs falls under this type.

95% of cases of heart disease in dogs are an acquired condition, whether that is due to infection, injury, or just the normal wear and tear that occurs on a dog’s heart throughout his lifetime. Most cases of heart disease in dogs are considered the acquired variety.

Heart Disease Conditions a Dog May Suffer From:

  • Chronic valvular disease, which is where heart valves get weak as they age and start to leak.
  • Pericardial disease, where the surrounding sac of the heart that protects the organ becomes fluid-filled and hinders the heart from beating normally.
  • Myocardial disease, which is a weakening of the heart muscle that causes enlargement.
  • Arrhythmias, which is essentially a heart “electrical problem” that causes a dysfunction of the heartbeat.
  • More rarely, dogs may be born with a heart murmur. Typically, if they are, the condition resolves itself on its own by six months of age.

Sometimes there are parts of the heart that aren’t fully developed with congenital defects. Sometimes a dog may be born with what is known as a hole in the heart. In both of these situations, the heart is unable to function the way it’s designed to function. This can make activities difficult for your dog, shorten his lifespan, and be a precursor to other related health problems. However, these congenital defects that cause heart disease are not nearly as common as the acquired types.

Signs of Canine Heart Disease

Heart disease can present with different signs and symptoms, depending on the type of heart disease and the severity of heart disease. Though it is scary, some dogs may display no symptoms at all until later stages. This is why regular yearly screenings for heart disease can be so helpful, as well as so important.

Your vet can check your dog on a regular basis for abnormalities like an irregular rhythm, or a heart murmur, and other warning signs that may be very subtle. Then, if your vet suspects heart disease, he or she can order further testing to confirm it and begin the appropriate treatment. Dogs with heart disease can eventually experience heart failure, so it’s important to take any warning signs seriously.

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Shortness of Breath

Shortness of breath is a very common sign of heart problems in dogs, and, in fact, may be one of the most noticeable. When your dog’s heart loses its ability to pump blood properly, your dog’s lungs pick up the slack, trying to draw in more oxygen to keep the blood flowing properly.

Breathing problems are especially concerning if you notice your dog panting and breathing harder at rest (especially on inhalation), or if you notice panting and breathing problems when they aren’t hot enough to warrant panting. Often, dogs will experience the most difficulty when inhaling rather than exhaling. Signs like these are especially worrisome and should not be ignored.

You may also notice whether your dog stands or sits with his legs spread wider than normal (like he is trying to widen his ribcage to inhale more air), and whether he is keeping his mouth open and neck stretched out, again to widen his airways.

Dogs that are having a very hard time getting oxygen may even fall asleep or try to fall asleep while standing or sitting, just because it’s easier to get air that way. Abnormal behaviors like these can all indicate a dog is experiencing respiratory distress, and should see a vet for care.


Coughing is also a very common sign of heart disease, especially in severe cases. However, because coughing can also be a sign of other problems related to your dog’s respiratory system, and may have nothing at all to do with heart disease. If you notice your dog coughs after drinking water, or while resting, or during and after play, or even just chronically throughout the day, your vet can provide clarity by running tests and making a definitive diagnosis.

Weight and Appetite Loss

Weight loss and loss of appetite in dogs can also be a sign of heart disease, especially if your dog experiences a reduction of muscle across the shoulders and hindquarters, and/or over the top of the back.

Even muscles on the top of the head can shrink and disappear. This is due to your dog’s body producing a hormone-like substance when suffering from congestive heart failure, and producing it in very high levels. When these levels get abnormally high, muscle loss is the result.


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Fainting is a common symptom of heart problems in dogs, often related to an abnormal heart beat. The spells are usually brief, and may resemble a canine seizure, but the dog will typically recover on his own quickly. During a fainting spell, your dog may briefly lose consciousness, and even lose control of his bowels.

A fainting spell usually only lasts about 30 seconds or so, and your dog is typically fully recovered within two minutes or less. Fainting can happen once in a day or several times throughout a day, but even one time is cause for concern. Your dog should be evaluated by your vet to determine the cause of the fainting spells.

Rear Limb Weakness

Another sign of heart disease some dogs may display is something known as “rear limb weakness”. Similar to when your dog has trouble breathing, when your dog’s body does not get enough blood pumped from the heart, it can cause a resulting weakness in his limbs. Rear limb weakness can be related to an abnormal heart rhythm, blood flow obstructions, a decrease in the heart pumping, or pericardial disease.

Behavior Changes

Just like with people, animals can experience behavior changes in response to health concerns. You know your dog the best, so if you notice your dog seems to be behaving abnormally, then it is worth seeing your vet to rule out any potential health issues, including heart disease!

Risk Factors of Heart Disease in Dogs

Fortunately, dogs are not like people, so things like a poor diet and smoking are not risk factors for heart disease in canines. Actually, smaller dog breeds that are over five years of age appear to make up the bulk of heart disease cases. Dogs with heartworm disease that causes heart disease make up a smaller portion of cases in dogs, despite heart worm disease being a condition that is highly preventable.

Another, even smaller percentage of dogs could suffer heart disease related to myocardial disease. This type of heart disease typically afflicts large breed dogs of all ages.

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Preventing Heart Disease in Dogs

Though a healthy diet and regular exercise may be commonly recommended to prevent heart disease in humans, this is not the same prevention plan recommended for dogs. In fact, most instances of heart disease in dogs are not preventable at all, except in the case of heartworm disease.

You can prevent heartworm disease by making sure your pet receives a heartworm preventative medication every year, along with wellness exams. Not only will you protect your beloved canine friend from heartworms and related heart disease, you will also keep them free of internal parasites. Regular heart worm medications help to keep your family safe too from things like zoonotic infections (diseases that are spread from animals to people).

Diagnosing Heart Disease in Dogs