Heart Murmurs in Cats

Vet Exam
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A feline heart murmur is usually detected during the course of a routine exam when the vet listens to your cat's heart using a stethoscope. There’s nothing mysterious about a heart murmur. It simply means the heart is making unusual sounds that could indicate an abnormality. If your vet determines that your cat has a heart murmur, you'll want to understand what causes the condition, how serious it is, and what your next steps might be.

Why Do Cats Have Heart Murmurs?

A heart murmur occurs when there's turbulence in the blood as it flows through the heart. The murmur is audible as a whooshing or swishing sound that occurs during the normal cycle of the heartbeat.

Murmurs are graded on a scale of 1 through 6, based on intensity or loudness. A louder murmur indicates more turbulence, and the loudest is audible in multiple places on the cat. A softer murmur may only be detectable in one place. It's important to know, however, that the grade of the heart murmur does not indicate the severity of the condition.

Additionally, the heart murmur may be constant, which means it's always audible at the same level of intensity or always sounds the same. On the other hand, a feline heart murmur may be dynamic, changing in intensity from time to time.

There are many different conditions that can cause a heart murmur in a cat. Some of these are serious and potentially life-threatening. Others are benign, not related to a disease, and may not affect your cat's health.

Heart Disease

Heart murmurs in cats may be related to structural heart disease. Your cat may have been born with a heart defect—known as congenital heart disease—such as pulmonic stenosis or patent ductus arteriosus.

It's also possible that your cat acquired heart disease later in life. Feline heart murmurs are often associated with cardiomyopathies or diseases of the heart muscle, which can cause abnormal heart function, including murmurs.

Extracardiac Conditions

A cat's heart murmur may also be linked to extracardiac conditions or conditions outside the heart. For instance, an extracardiac condition may be present when the cat has a fever or infection, though it may occur in cats that are pregnant, obese, or emaciated as well.

Murmurs are also a common symptom of:

  • Anemia: A condition caused by low red blood cell levels.
  • Hypoproteinemia: An indication of low protein levels in the blood.
  • Hyperthyroidism: A condition caused by an enlarged thyroid gland that produces too much hormone, which can lead to cardiomyopathy.

Innocent Murmurs

After a thorough examination, your vet may find that your cat is in perfect health. In these instances, the murmur is called an innocent or physiologic heart murmur. These benign murmurs are generally low in intensity and don't occur with other signs or symptoms that indicate a disease or illness.

Innocent murmurs are common in young kittens—especially when they're going through a growth spurt—and generally stop at around 4 or 5 months of age. Adult cats may have temporary murmurs as well, which are often due to stress that causes an increase in the heart rate. Since a vet visit may cause some anxiety in your cat, your vet will likely take this into account if she notices a faint murmur during a checkup.

Treatment

When they detect a heart murmur, vets must rely on diagnostic testing to find out why the heart murmur is there.

In cats, heart murmurs are usually best evaluated with an echocardiogram. This ultrasonic examination allows the veterinarian to assess your cat's heart muscle and other critical structures to obtain an accurate diagnosis.

Although a cat owner may decide to wait and do nothing other than observing his cat, this may not be a wise course of action. Cardiomyopathies and some of the other heart diseases associated with a murmur can develop into severe, life-threatening conditions very quickly. In some cases, sudden death may even occur.

Treatment options vary, depending on the actual cause of the murmur. If it's found to be benign, no treatment is necessary, and your vet may elect to simply monitor your cat's health more regularly. However, if it's due to an underlying health issue, your vet may recommend surgery, medication, a special diet, or some other type of specialized care.

When a heart murmur is properly addressed, it may completely resolve over time.