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Heart Disease in Dogs: Common Signs, Causes, & Treatments

Written by: Jennifer Lesser

Last Updated on February 10, 2024 by Dogster Team

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Heart Disease in Dogs: Common Signs, Causes, & Treatments

As our beloved four-legged friends age, they unfortunately become more susceptible to an array of potential health conditions, including heart disease. “Heart disease occurs when the heart is unable to pump blood effectively. It’s more often seen in older dogs, but dogs of any age can be affected,” explains Dr. David Dilmore, a veterinarian with Banfield Pet Hospital.

According to Dr. Jessica Romine, a veterinarian with BluePearl Veterinary Partners in Southfield, Michigan, heart disease is one of the more frequently diagnosed issues in dogs — however, not all heart diseases will actually lead to heart failure. Approximately 10% of all dogs will develop some degree of heart disease in their lifetime. “The incidence goes up significantly with age, with 20 to 25% of dogs between nine and 12 years being affected, and 75 percent of dogs over 16 years old being affected,” she adds.

Causes of Heart Disease in Dogs

So what actually causes heart disease in dogs? There are two main categories of canine heart disease: congenital and acquired disease. “Congenital defects are problems a puppy is born with,             and generally uncommon,” Dr. Romine explains. “The most common sign is a heart murmur; some puppies will have heart murmurs that go away with age.” However, 95% of canine heart disease cases are acquired — meaning it develops later in your pet’s life.

According to Dr. Rachel Walton, a veterinarian at University Veterinary Hospital and Diagnostic Center in Salt Lake City, Utah, there are two common types of acquired heart disease in dogs: mitral valve disease and dilated cardiomyopathy. “Mitral valve disease accounts for about 75% of cases of acquired heart disease in dogs, and is caused by the degeneration of the atrioventricular valve on the left side of the heart, which leads to a back flow of blood through the valve … and can eventually cause congestive heart failure,” she explains.

This form of heart disease is most commonly seen in older dogs, and while any breed can be affected, it tends to be more prevalent in small to medium breeds including Miniature and Toy Poodles, Cavalier King Charles Spaniels, Cocker Spaniels, Miniature Schnauzers, Dachshunds, Shih Tzu, Lhasa Apso, and various Terrier breeds. “The exact cause is unknown, but a genetic component is suspected in some of these breeds,” she adds.

Dilated cardiomyopathy is characterized by a decreased contractility of the heart, causing the chambers of the heart to dilate and results in heart failure. This form of heart disease is most common in large and giant breed dogs, and has been shown to be genetic in breeds including Portuguese Water Dogs, Irish Wolfhounds, Great Danes, Newfoundlands, Standard and Giant Schnauzers, and Doberman Pinschers. Taurine deficiency has also been linked to dilated cardiomyopathy.

“Additionally, nutritional causes of heart disease are currently being investigated, as cases of dilated cardiomyopathy have been reported in dogs being fed some grain-free diets, especially those containing a high percentage of pulses like peas, lentils, fava beans and garbanzo beans,” Dr. Walton adds. “The exact cause of this has not been determined and is still being studied.”

Wheat. Photography ©rasilja | Thinkstock.

According to Dr. Dilmore, heartworm disease can also cause damage to your dog’s heart and ultimately block the outflow of blood. “Talk with your veterinarian about year-round heartworm prevention, as once a pet becomes infected, permanent heart and lung damage can occur,” he advises.

Symptoms of Heart Disease in Dogs

Unfortunately, most dogs who are impacted by heart disease will not necessarily show clinical signs at home, but your pet’s veterinarian may notice a heart murmur or arrhythmia during a physical exam.

“If symptoms are noted at home, they might include lethargy, reduced exercise tolerance, decreased appetite, weight loss, coughing, rapid respiratory rate, and difficulty or distressed breathing. Syncope, or collapse, can also be noted in some cases,” Dr. Walton says.

Diagnosing Heart Disease in dogs

According to Dr. Dilmore, a veterinarian may diagnose a case of heart disease through a physical exam, if they’ve found that your pet has an increased heart rate, heart murmur, heart arrhythmias, an increased respiratory rate, or increased lung sounds. They may also use diagnostic tests such as chest x-rays, an electrocardiogram (ECG or EKG), an echocardiogram (an ultrasound of the heart), or blood work.

Regular veterinary visits are critical for detecting heart disease early, when it is most treatable,” Dr. Romine asserts.

Treatment for Heart Disease in Dogs

If your pet is diagnosed with heart disease, medication would generally begin only once they are deemed to be in congestive heart failure. “Medications are prescribed to reduce fluid accumulation in the lungs, reduce the workload of the heart, and optimize the contractility of the heart,” Dr. Walton explains. “Dogs in congestive heart failure are monitored regularly with exams, x-rays, and blood tests.”

According to Dr. Romine, drugs such as Pimobendan can be used to help the heart contract more strongly, and the latest recommendations are to start this drug earlier in the course of heart disease. Diuretics such as Furosemide are used to help prevent and lower the amount of fluid accumulating in the lungs, while ACE inhibitors, such as Enalapril, are used to open the arteries and decrease the amount of work the heart has to do. Diuretics and ACE inhibitors can occasionally affect the kidneys; this is monitored by regular kidney evaluation with blood testing. “Additional drugs may be prescribed to control cardiac arrhythmias (irregular heart beats), but dogs require beta blockers far less often than humans do for heart disease,” she adds.

Asymptomatic dogs may also be started on medication to slow the onset of heart failure if they have had an echocardiogram and meet certain criteria. “Most dogs with a heart murmur only are not started on any treatment,” she explains. “Continued monitoring of exams and chest x-rays is generally recommended.”

A vet patting a dog on the exam table.
A vet patting a dog on the exam table. Photography ©BraunS | Getty Images.

The prognosis of heart disease will depend on the underlying cause and severity of your dog’s condition. In addition to treatments such as medications to decrease blood pressure or decrease anxiety, other options may include chest taps, oxygen therapy, or dietary changes, Dr. Dilmore notes.

According to Walton, while not all dogs with a heart murmur caused by mitral valve disease will go on to develop congestive heart failure, the prognosis of dogs with mild-to-moderate congestive heart failure secondary to mitral valve disease is fair, with only a one to two year survival rate. Dogs that present initially in severe congestive heart failure have a more grim prognosis, with only 25 percent of dogs surviving one year. Dilated cardiomyopathy has a variable prognosis, but once a dog is in congestive heart failure, the survival is generally less than 12 months.

Preventing Heart Disease in Dogs

While this disease is not necessarily preventable, there are some things pet owners can do to help lower their pet’s chances of being affected. “Heart disease may not always be preventable, but early diagnosis and treatment is very important,” Dilmore says. “Twice yearly exams by a veterinarian are important to screen for any risk factors and intervene early in the disease process.” Year-round heartworm prevention, professional dental cleanings, and home dental care can also help decrease the risk of heart disease in dogs.

“The most important thing you can do for your dog is to watch for changes in their activity level, behavior, and breathing, and take them in for regular routine veterinary care,” Romine concludes. Early detection is the key to ensuring you have the largest numbers of options for caring for your dog—and their heart.”

Learn more about heart disease and other serious conditions at

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