Heart murmur in pets

What It Is

A heart murmur is an extra whooshing or swishing sound the vet hears between normal heartbeats through a stethoscope, caused by turbulent blood flow inside or near the heart. It is a physical exam finding, not a diagnosis in itself, and many pets with a murmur feel completely normal at home. Murmurs are graded on a scale from one to six based on how loud they are, and a louder murmur does not always mean a more serious problem. Some murmurs are present from birth, while others develop later in life.

Common Causes

In dogs, the most common cause is a leaky heart valve that develops slowly with age, particularly in small breeds. Cats more often develop murmurs from thickening of the heart muscle, a condition that does not always show up as a murmur but frequently does. Puppies and kittens can be born with a structural defect in the heart, and some of these are found on a first puppy or kitten check and resolve or need monitoring as the animal grows. Occasionally a murmur reflects anaemia rather than a heart problem itself.

When It Is an Emergency

A newly found murmur is not usually an emergency by itself. It becomes urgent if your pet is also breathing hard, coughing persistently, has pale or blue gums, collapses, or seems suddenly weak or exhausted, since these suggest the heart is struggling to keep up. If your pet is bright, eating, and breathing normally, the murmur can be investigated through a scheduled work-up rather than same-day care.

What the Vet Will Do

The vet will usually recommend an echocardiogram, an ultrasound of the heart, to see which valve or chamber is involved and how well the heart is pumping. Chest X-rays and blood pressure measurement often accompany this to check for fluid in the lungs or related strain. Blood tests can rule out anaemia as a cause. Based on the results, some pets need no treatment beyond monitoring, while others start medication to support heart function.

Home Care and Prevention

There is little an owner can do to prevent age-related valve disease, but keeping a pet at a healthy weight reduces strain on the heart. Once a murmur is diagnosed, regular rechecks let the vet track any change over time. Watch for new coughing, tiring more easily on walks, or breathing changes at rest, and mention these promptly at follow-up visits.