Heart murmur in dogs: symptoms and how to treat it 

A beautiful Westie named Cossy loved to bark and chase after any ball. Ever since she arrived to live with her family, she has been full of energy. As the years passed, she became an excellent "lady" dog, always wanting to go out for a stroll and being the center of attention. One day, she started slowing down, not wanting to run much or take long walks – she tired quickly. Her owners thought it was expected as she grew older until she refused to leave the house entirely. Her folks took her to the doctor, and she was diagnosed with heart disease. The doctor explained that this type of condition is hard to detect and often happens in dogs. This news surprised Cossy's family, and they were determined to learn more about it.

Woman examining dog

Many pet owners would feel just as Cossy’s family. They hardly know anything about heart disease in their furry friends.  Let's go through some information that can help you understand it better.

Heart disease, how does it work?

The most common cardiac disease in dogs is Myxomatous Mitral Valve Disease (MMVD). MMVD happens when the heart has a leak in one of the heart valves, preventing blood from getting pumped correctly. This creates a murmur. A heart murmur is a sound caused by turbulence in the heart – the heart momentarily doesn’t contract correctly. This preclinical condition accounts for 75 to 80 percent of MMVD clinical cases1, which is the primary cause of morbidity and mortality in dogs. It is important to remember that there is no way back once the abnormality progresses – MMVD is chronic. Regardless, following medical treatment can help keep the disease at bay. 


heart graphic


Small and medium-sized dogs are mainly affected1. Some breeds are more prone to this disease such as the Cavalier King Charles spaniels, the dachshund, poodle, chihuahua, and cocker spaniel. Let’s not forget about age, an essential factor when talking about MMVD. The incidence of heart disease increases 60 percent, or more, for dogs over seven years of age2.


Heart murmur identification

Like humans, the heart is the first and most important thing to be checked in regular visits. When you go to the veterinarian, the vet's first step is to listen to your pet’s heart with a stethoscope. As a result, vets can pinpoint heart disease on time. It is necessary not to miss these appointments to maintain reasonable health control.  

Listening to the heart is no easy task. Nevertheless, with it, veterinarians can detect if a slight whistle could indicate a heart murmur. Echocardiography, a heart ultrasound, can be made for confirmation and stage identification. Unfortunately, it is not yet widely available and is expensive for pet owners. However, having an x-ray is quite common in vet clinics around the globe.

Heart disease stages

There are four stages proposed by the American College of Veterinary Internal Medicine (ACVIM) Specialty of Cardiology consensus panel for this disease: stage A, stage B1, stage B2, stage C, and stage D. It is crucial to identify the stages B1 and B2 to know which treatment to implement, considering that the effectiveness of interventions to treat MMVD is quite different in these two stages.

Heart disease stages in dogs

Stage A refers to dogs that are not yet affected but are “at-risk” because they are, for example, one of the breeds listed above. At stage B1, there is a heart murmur but no other problem. This is the longest part of the disease – no treatment is required, but a 6-monthly checkup is essential. By stage B2, the heart is changing in shape and enlarging. Treatment is vital to slow down the development of clinical signs and keep the pet healthy. 

Monitoring the heart in intervals of 3-6 months is now more important than ever to detect if the disease progresses to stage C. A key sign is an increase in the patient’s resting respiratory rate (RRR). Therefore, training dog owners to monitor respiratory rate and keep track of it over time is helpful.

Stage D of this disease occurs when the clinical signs of heart failure are more substantial, manifesting in stronger symptoms such as arrhythmias, despite receiving therapy. In this case, treatment needs to be adjusted to control this new development.

Treatment without medicines, is it possible?

There are some ways of treating cardiac disease apart from medical treatment. Some options include surgery, managing a high caloric and tasty diet that can compensate for the dog’s weight loss and loss of appetite, and exercise. Though exercise has not been scientifically approved as beneficial for dogs with this disease, it is recommended as the benefit of training is noticeable in humans and animals. Talk to your veterinarian about it to make sure your dog has the capacity and energy to cope with it, as exercise levels vary depending on the current stage of the disease.

As we can see, if detected in time and well treated, a dog with heart disease can live longer with a better quality of life than if it didn’t have the treatment. Cossy’s family can now administer a long-term treatment regime and enjoy more happy moments together.



1 Hezzell M. Pathology and prognosis of canine myxomatous mitral valve disease. In pract.2018 Mar; 40 (S1): 3-6. 
2 Indian J. Anim. Hlth. (2019), Cardiac disease in Dogs. 58(1): 01-20.