cardiomyopathy in dogs and cats

Cardiomyopathy is not just a human condition. Dogs and cats can also suffer.

When Jonathan took his seven-year-old boxer cross, Carlyle, to a friend’s house for a visit, he had no inkling it would be his dog’s last trip. While the friends were chatting over dinner, Carlyle suddenly collapsed. Jonathan rushed him to an emergency vet, but Carlyle died before they arrived. It turned out to be heart failure. Stunned and devastated, Jonathan made it his mission to research all he could about cardiomyopathy — otherwise known as heart disease — before adopting another dog.

As in Carlyle’s case, cardiac issues in companion animals is often a silent killer. By the time a dog or cat shows classic symptoms like lethargy, wheezing, croupy coughing (a liquid sounding cough) or exercise intolerance, the disease is often far advanced. And since an enlarged heart can’t be detected with a stethoscope, heart disease can be present and undiagnosed by your veterinarian long before your dog or cat shows clinical symptoms of illness.

Cardiomyopathy is the scientific term for a diseased heart muscle. “Cardio” means heart, “myo” is the Latin word for muscle, and “pathy” means disease. There are different types of cardiomyopathy, including hypertrophic cardiomyopathy, dilated cardiomyopathy, restrictive cardiomyopathy, and unclassified cardiomyopathy.

Dogs — dilated cardiomyopathy

Dogs most often develop dilated cardiomyopathy (DCM), typically between the ages of four and ten. DCM describes a diseased heart muscle that doesn’t contract or pump efficiently. As the disease progresses, the heart chambers become enlarged, heart valves may leak, and congestive heart failure can develop.

The cause is unknown. Unlike heart muscle dysfunction in humans, when it happens in animals, it’s rarely the result of chronic coronary artery disease. Nutritional deficiencies of taurine or carnitine have been linked to DCM in certain breeds. Once in a while, DCM-like heart muscle deficiency develops secondary to an identifiable cause like exposure to a toxin or heart infection.

Male dogs seem to develop DCM more often than female dogs. And certain breeds, often larger ones, are more prone to the condition, including the Afghan hound, boxer, cocker spaniel, Doberman pinscher, great Dane, Irish wolfhound, Saint Bernard, and Scottish deerhound.

Symptoms of DCM

Early in the disease process, there are often no obvious symptoms. Some dogs may experience a reduction in exercise tolerance. Sometimes a slight heart murmur or other abnormal heart sounds or rhythms can be detected by a veterinarian.

As the disease progresses, the heart’s ability to pump declines, so blood pressure in the veins behind the heart can increase. Congestion of the lungs and fluid accumulation are common, and indicate heart failure. Dogs with DCM-induced heart failure often have left-sided congestive failure.

Symptoms you might notice include a decreased ability to exercise, rapid tiring, increased respiration, and excessive panting and coughing. There may be sudden and recurring episodes of weakness or fainting. Some dogs with DCM have enlarged abdomens and heavy breathing due to fluid accumulation.

Sudden death can also occur from heart rhythm disturbances, even though there aren’t obvious external signs of heart disease. Advanced signs of heart failure include labored breathing, reluctance to lie down, and an inability to get comfortable. A worsening cough, reduced activity level, loss of appetite, as well as collapse, can all be symptoms.

Treatment options

Treating dilated cardiomyopathy in dogs focuses on improving heart function and treating symptoms of congestive heart failure.

Conventionally, ACE inhibitors are often prescribed to slow down the progressive changes to the heart that can lead to heart failure. As the disease progresses, different drugs can be used to help the heart contract. Drugs can be administered to slow down a rapid heart rate, to manage accumulation of fluid in the lungs, or to dilate blood vessels. There are also drugs that can help the heart beat and pump more efficiently.

Unfortunately, side effects from these drugs are very common and can include electrolyte imbalances, reduced appetite, diarrhea and vomiting, depression, a drop in blood pressure, and kidney disease. And because the disease is irreversible and heart failure is typically progressive, the drugs and dosages required to manage DCM usually increase over time.

Alternative therapies that can support heart function in dogs with DCM include herbs such as hawthorn berry and cayenne. Supplements can also be very beneficial, and include acetyl L-carnitine, the amino acid taurine, arginine, D-ribose, Omega-3 fatty acids, and ubiquinol, the more bio-available form of CoQ10.

Alternative therapies that can support heart function in dogs with DCM include herbs such as hawthorn berry and cayenne.

Cats — hypertrophic cardiomyopathy 

In cats, hypertrophic cardiomyopathy (HCM) is the most common type of primary heart disease, accounting for 85% to 90% of all cases. It is often inherited; in fact, there’s now a test available for a specific gene mutation in Maine coons and ragdolls. Purebred cats such as Persians, other Oriental breeds, and American shorthairs are also predisposed to HCM. However, it’s the regular housecat that is most commonly diagnosed with the condition. Cats usually develop HCM in midlife, but it can occur at any age.

The word “hypertrophic” means thickened, so HCM is a condition in which the walls and ventricles of the heart become too thick, or hypertrophied. The severity of the condition depends on how thick the muscle wall gets. As HCM progresses, the actual structure of the heart changes and heart function is affected. Thickened muscle walls become less flexible, and the left ventricle can no longer relax or stretch efficiently to fill with blood.

In rare cases, the thickening of the heart causes an arrhythmia that can bring on sudden death. Some cats develop feline aortic thromboembolism, also called FATE, which is a blood clot that forms in the aorta and blocks the flow of blood, usually to the back legs. This causes sudden paralysis, a tremendous amount of pain for the cat, and even death.

Symptoms of HCM

Symptoms vary and depend to some extent on the severity of the disease. Cats with mild disease don’t always have symptoms. But in a cat with significant HCM, there are usually obvious signs.

Cats mask illness very well, so until this condition is severe, even a cat with significant disease may have no symptoms, or very mild symptoms that don’t seem to be indicative of heart disease.

In cats with obvious symptoms, there can be respiratory distress caused by congestive heart failure, or leg paralysis due to a blood clot. Cats suffering congestive heart failure don’t cough like people or dogs do. Instead, they tend to breathe through an open mouth, and may even pant, especially during exertion.

Treatment options

There is no cure for HCM. However, if the heart problem has developed as a result of another underlying issue, treatment of the primary disease can result in partial or complete resolution
of the HCM.

Diuretics and ACE inhibitors are used in mainstream medicine to treat congestive heart failure in cats. In cases of severe fluid buildup in the chest cavity, it may be necessary to remove the fluid with a catheter.

Drugs to reduce the likelihood of blood clots are sometimes used on HCM patients at risk for thromboembolism. These drugs must be closely monitored to prevent hemorrhage, and there’s no guarantee that clots won’t form even with the medications. I much prefer using a natural supplement called nattokinase to reduce the risk of blood clots.

I’ve had excellent success in slowing the disease by using a combination of ubiquinol (the reduced form of CoQ10) and certain amino acids, including taurine, L-arginine, and acetyl L-carnitine. I also use heart glandulars and herbs, including hawthorn.

Because heart disease in dogs and cats is often insidious and difficult to detect, it’s not easy to determine whether or not your companion will develop it. However, there are things you can do to help protect his health (see below) and keep him by your side!

What can you do?

  1. A healthy lifestyle and regular veterinary checkups are vital, especially if you have a higher-risk breed.
  2. Diet is extremely important – a balanced, fresh food, meat-based diet rich in naturally-occurring amino acids, and free of all fillers such as grains and unnecessary carbohydrates, is the best form of nutrition for animals that have cardiomyopathy or might be prone to it.
  3. Be watchful for any uncharacteristic symptoms such as lethargy, easy tiring, and breathing issues, even if they seem subtle, and get your animal examined by the vet as soon as possible.
  4. Talk to an integrative or holistic veterinarian about supplements that could help keep your dog or cat’s heart healthy.


Veterinarian Dr. Karen Shaw Becker received her degree from the Iowa State College of Veterinary Medicine. She owns/operates Natural Pet Animal Hospital, Feathers Bird Clinic, TheraPaw Rehabilitation and Pain Management Clinic and Covenant Wildlife Rehabilitation in Illinois. She co-authored Real Food for Healthy Pets and hosts a holistic animal wellness website (