The heart is the engine of the body. Simply put, the heart is a pump, and it needs to be able to generate enough pressure to push blood throughout the body, including to the lungs, where blood picks up oxygen. It also needs to be able to keep blood moving forward and maintain a steady rhythm.

In about 10 percent of dogs and cats, one of these functions of the heart doesn’t work properly. While heart problems can affect any dog or cat, some breeds, including small dogs, boxers, and Dobermans, as well as Maine coon, ragdolls, sphynx, Persians, and British shorthairs, are prone to developing heart disease.

Allison Masters, an assistant professor of comparative cardiology in the College of Veterinary Medicine’s (CVM) Department of Veterinary Clinical Sciences, wants to help pet owners catch heart problems in their pets and intervene early, before the issues lead to more serious consequences, such as heart failure.

“While heart failure can be managed quite well with medications, it is a medical emergency in pets and can be fatal,” Masters says. “What I would like to do is focus on how we can detect heart disease in our pets before they start showing signs of heart failure.”

Signs of heart disease in pets

While it’s always best to detect problems as early as possible, sometimes heart problems go undetected until the issue is more advanced. If you see any of these warning signs, bring your cat or dog to your veterinarian as soon as possible.

“If we are seeing signs of heart disease in our pets, that could mean that they have heart disease that has ultimately caused their heart to start to go into failure,” Masters says.

1. Issues pumping blood

If your pet’s heart is struggling to pump blood throughout its body, it may have decreased energy, weakness, or may be less playful than usual. They may not be able to go as far on walks or may have pale, whitish gums—they should be pink. In severe cases, your pet may collapse.

2. Issues controlling the direction of blood flow

As mentioned, heart valves keep blood flowing forward and prevent it from backing up into the heart. If valves weaken or stiffen, this process can cause fluid to back up into abnormal parts of the body, such as the lungs.

If this happens, your pet could have difficulty breathing or fits of coughing or gagging; however, Masters says that if your pet only coughs or gags after they eat, that this is not a sign of heart failure. They may also have a distended belly—think potbelly appearance—or faint or collapse.

3. Problems delivering oxygen throughout the body

Since blood carries oxygen throughout the body, a weakened heart muscle can prevent a sufficient amount of oxygen from reaching other organs. These warning signs are similar to other heart issues and include difficulty breathing, coughing or gagging, decreased energy, and weakness. But a telltale sign that your pet may not be getting enough oxygen due to a heart problem is having blue gums and tongue.

4. Arrhythmias

Arrhythmias are disruptions in heart rhythms that cause the heart to beat too slowly, too fast, or irregularly. Arrhythmias can cause decreased energy and weakness, as well as fainting or collapsing.

Signs of heart disease in cats

All of these warning signs apply to both cats and dogs, but when cats have heart disease, they are also at risk of developing blood clots in their heart.

“If those clots leave the heart, those will result in things like stroke, or more commonly, they will go to the cat’s legs,” Masters says. “That will look like a cat suddenly not being able to use one or more of its legs.”

If your cat has pale or purple paw pads on at least one leg, or is in pain or uncomfortable—they may be vocal about it—they may have a blood clot.

“Blood clots are an emergency and warrant an emergency room visit, where veterinarians can help make your cat comfortable and discuss options for your cat,” Masters says.

Detecting heart disease early

The best tool pet owners have to detect heart disease in pets is to keep up with annual vet visits, even if their pet seems perfectly healthy.

“Your veterinarian will use a stethoscope to listen to your pet’s heart and lungs,” Masters says, noting that this will allow the veterinarian to detect signs of abnormal heart valves, called a heart murmur, or arrhythmias. “If your vet detects any of these abnormalities, they may order some tests based on what they are hearing.”

These can include a chest X-ray to look at the heart’s size and shape, or an electrocardiogram (EKG), which can better detect arrhythmia. In some cases, a blood test called a cardiac biomarker test, is needed to detect elevated levels of certain hormones and proteins that indicate heart conditions.

Based on the results, your veterinarian may refer your pet to a veterinary cardiologist.

Heart disease risk increases with age

Just as is the case with humans, cats’ and dogs’ risk of heart disease goes up drastically as they age—between 60 and 75 percent of senior dogs develop heart disease.

“Many heart conditions don’t affect animals until they are older,” Masters says, noting that some high-risk breeds, including Boxers and Dobermans, need to get annual cardiovascular examinations by a veterinarian.

Annual heartworm testing also becomes more important in older dogs and cats, since aging bodies and compromised immune systems can make pets more prone to the parasitic worms.

Intervening early

The good news is that there are some medications that can slow down the progression of heart disease in dogs, especially if it’s caught early, and extend the amount of time it takes for these problems to become heart failure.

The most common heart disease in dogs is myxomatous mitral valve disease, which causes valves on the left side of the heart to thicken and leak. The second most common is dilated cardiomyopathy, in which the left ventricle—which is responsible for pumping blood through and out of the heart—becomes weak. Masters says a drug called pimobendan has been shown to slow the progression of both diseases.

“It’s a medication we commonly use in dogs with early heart disease. It can slow down the time between diagnosis and when the dog develops heart failure,” Masters says.

Unfortunately, there have not been any medications to date that have been shown to slow down the progression of any cat heart conditions. However, cats who have heart disease can take blood thinners to prevent clots, which can be fatal, Masters says.

In March 2025, the FDA did conditionally approve a drug that has been shown to manage ventricular hypertrophy—when the heart becomes thickened and enlarged—in cats.

“That is the most common heart disease we see in cats; it can affect up to 15 percent of cats in their lifetime, so I’m really excited to see this,” Masters says.

Felines that have been diagnosed with ventricular hypertrophy can still enroll in the HALT clinical trial investigating this conditionally approved drug—just note that enrollment requires a referral from a veterinarian.

Preventing heart disease in your pet

There are also a couple of things you can do to prevent heart disease in your pet, but detecting any heart problems as early as possible still has the biggest effect on heart health.

“The best case scenario would be preventing heart disease in our pets to begin with,” Masters says. “Unfortunately, the vast majority of heart conditions we see in pets cannot be prevented; they are inherited, so modified lifestyle factors really can’t prevent them.”

Getting genetic testing done can help pet owners understand if their pet is genetically predisposed to developing heart disease. For any breed, giving pets their heartworm drugs year-round is a big way for pet owners can prevent disease. It’s also a good idea to get your dog tested for heartworm at their annual veterinary check-up, especially if you’ve missed a dose of medication, Masters says.

When it comes to diet, prevention is nuanced, Masters says, but eating a balanced diet is very important for heart health. She advises pet owners to avoid dog foods that contain peas and pea products, legumes, or sweet potatoes.

“Nutrition labels for our animals are completely different from the food labels we look at for ourselves,” she says. “A fully balanced diet admittedly is quite nuanced, but your best bet is to feed a commercial diet that meets WSAVA nutrition guidelines or a homemade diet under the direction of a veterinary nutritionist.”

Watch Masters’ full Animal Health Education Series talk on heart disease in dogs and cats.