Dog with heart murmur

My vet says my six-year-old Cavalier King Charles Spaniel has a heart murmur. How serious could this be, and is it something that I should be worried about?

Paul Manktelow advises…

Heart murmurs are commonly diagnosed in dogs, particularly in the Cavalier. Usually they are simply something to be aware of, which your vet will re-check during routine consultations. A heart murmur in smaller dogs, such as Cavaliers, is generally caused by mitral valve disease. These valves push blood through the heart, and around to the rest of the body. When they are diseased, they become thickened and degenerate, which prevents the valves from closing properly.

This causes blood to flow backwards in the wrong direction, towards the lungs, creating the murmur that can be heard with a stethoscope. When a murmur isn’t causing symptoms, it is not something to be immediately concerned about, but should be monitored at home. The symptoms of a heart murmur becoming significant can include coughing, not wanting to go out for exercise, not wanting to eat or drink, and difficulty breathing. If you notice any of these signs, it would be a good idea to visit your vet to decide on further action.

Further diagnostics often involve chest X-rays and an ultrasound scan of the heart as a minimum. This will help your vet decide on the significance and grade of the heart murmur – grade one being the least severe, up to grade six, which is the most severe – and therefore what forms of treatment should be provided. Medications given for heart murmurs cannot cure the underlying problem, but they can help the heart to contract more efficiently. This will subsequently help to prevent the build-up of fluid in the lungs from blood flowing in the wrong direction.

With effective treatment, heart murmurs can be controlled very effectively – from months to years, depending on the severity.


  1. Should I have a scan for my Cavalier King Charles diagnosed at stage 4 heart murmur or wait till signs of deteriation with her health. She’s 7 years old thank you


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