What Is a Heart Murmur, and Should You Worry?

In this guide

During a routine visit, your vet will use a stethoscope to listen to your dog or cat's heart. A normal heartbeat has a steady, even rhythm, whereas an irregular one breaks that rhythm, either with an extra beat or with a distinctive "whooshing" sound.

An irregular heartbeat, or an unusual sound of this kind, could indicate a heart murmur. Before assuming the worst, it is worth knowing that heart murmurs come in many forms, and having one does not automatically mean your pet is in danger. Some animals are born with a murmur, while others develop one over the course of their life, and if caught early, murmurs can generally be managed.

Once a vet identifies a murmur, the next step is looking for other symptoms to help pinpoint its underlying cause.

Three types of heart murmur

A normal heartbeat has an even, countable rhythm, but a murmur interrupts that regularity. Blood carries oxygen and nutrients throughout the body, so when that flow is disrupted, as it is with a murmur, it is worth finding out why. A murmur can slow blood flow or make it irregular, and murmurs are classified into three types based on timing:

1. Systolic, occurring when the heart contracts
2. Diastolic, occurring between beats
3. Continuous, occurring throughout the cycle

Once a vet hears a murmur, they will listen more closely to categorise it and may also grade it by loudness. Some murmurs are so faint they can only be picked up with a stethoscope, while others are audible simply spending time near the pet.

What else matters

Beyond timing and loudness, a vet will want to establish exactly where the sound originates. Combined with the animal's age and other health factors, knowing whether the murmur comes from the left or right side of the heart can offer further insight. In older dogs, for instance, a murmur from the lower left of the chest may point to degenerative mitral valve disease, while a murmur audible in the neck can suggest aortic stenosis.

Heart murmurs can produce unusual vibrations, disrupted blood flow and even blockages, but pinpointing the exact source can be genuinely tricky, and location alone is not enough to reach a diagnosis. Vets will also weigh up the animal's age and any other symptoms present.

Puppies can be born with a murmur that resolves within the first few months of life, known as a congenital murmur. As dogs age, they can also develop heart disease, of which a murmur can be one symptom; these are referred to as acquired murmurs.

What can be done about a heart murmur?

There is no treatment aimed specifically at the murmur itself. Any treatment instead targets the other symptoms and underlying health conditions present. Some vets may recommend chest X-rays to get a clearer sense of the heart's condition, though the approach is always tailored to the individual case.

Are some breeds more prone to murmurs?

Certain breeds do carry a higher risk of heart murmurs and related conditions. King Charles Cavalier Spaniels and toy poodles are prone to degenerative mitral valve disease, a condition that enlarges the heart as blood flows backward and can lead to coughing and a reduced interest in exercise. Dachshunds are prone to developing leaky valves, usually manageable with medication and a healthy weight. It is not only small breeds either: boxers and golden retrievers carry increased risk too, and among cats, Maine Coon, Siamese and Persian cats can be susceptible to a condition known as hypertrophic cardiomyopathy.

There is, in short, no single conclusive treatment for heart murmurs, and your vet will develop an individual plan for your particular dog or cat. Regular veterinary visits remain the best way to keep track of your pet's heart health; an annual wellness check is generally recommended before the age of five, moving to twice-yearly visits after that, since pets age considerably faster than humans and a great deal can change in six months.

Article content © S Vejay Anand. All rights reserved.