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Heart Murmur in Cats, Symptoms, Causes, Diagnosis and Treatment

Updated on April 25, 2015
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Trained in dentistry, Sree is currently studying lab sciences. She enjoys researching various health topics and writing about her findings.

There are a lot of common conditions in cats people tend to overlook, which happen to indicate a more serious problem, like heart murmurs. Although heart murmurs is a common condition that even kittens experience temporarily, they are linked with the possibility of a heart ailment. In some cats, heart murmurs come and eventually disappear. For other cats, it indicates an underlying and possible severe heart condition.

What are Heart Murmurs?
Heart murmurs are only audible when listening to a cat's heart with a stethoscope. These "murmurs" are extraordinary sounds in addition to the Lub - Dub rhythm of the heart. It is made by unusually turbulent blood flow in the cat's heart. It is not a disease but is considered a symptom.

Heart Murmur in Cats, Symptoms, Causes, Diagnosis and Treatment
Heart Murmur in Cats, Symptoms, Causes, Diagnosis and Treatment | Source

How Heart Murmur Sounds Occur

There are four chambers in a cat's heart: the tricuspid valve, the pulmonic valve, the mitral valve and the aortic valve. Blood flows through the tricuspid valve first, then the pulmonic valve before obtaining oxygen from the lungs. Oxygenated blood flows back to the heart through the mitral valve and finally the aortic valve for body distribution. Heart murmurs are turbulent-like sounds that are created by disturbed blood flow in either the heart valves, ventricle or atrium. They may be caused by increased blood flow, dilated pathways or the clotting of blood.

Causes of Heart Murmurs

Heart murmurs are caused by changes in the heart's normal blood flow. They can occur when blood leaks in the heart valves or when there are heart muscle defects like contractions or dilation. When either the blood vessels or heart chambers narrow, heart murmurs will occur as well.

  • Some cats are born with heart murmurs, this is called ‘innocent' heart murmurs. Kittens are known to have them without any disease whatsoever, and it gradually disappears as the kitten grows older.
  • Heart murmurs in adult cats not indicating a disease are called ‘physiological' murmurs. They are often caused by stress and gradually disappear when the cat's environment is changed.
  • Heart murmurs can also be developed over the cat's lifetime but benign.
  • Heart murmurs may indicate an underlying heart disease. It may indicate a blockage or clogging of the arteries, causing the disturbance in the heart's blood flow.
  • Other conditions such as anemia can also cause heart murmurs, accompanied by other symptoms like lethargy and anorexia.
  • Cardiomyopathies can cause heart murmurs, these are diseases of the heart muscles.
  • While it is rare in cats, heart murmurs may be a sign of a heart worm disease.
  • Some kittens born with heart murmurs may have it as a congenital disease.

Systemic illnesses may also cause heart murmurs as well as a thyroid disease or simply high blood pressure.

How Heart Murmur Sounds Occur, Causes, Symptoms
How Heart Murmur Sounds Occur, Causes, Symptoms | Source

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Other Symptoms to Watch Out for

Heart murmurs are only one symptom and often accompanied by other symptoms should there be a significant underlying problem. Here are the following accompanying symptoms to watch out for:

  • Rapid breathing or difficulty in breathing
  • Lethargy or consistent weakness
  • Loss of appetite and/or unexplained weight loss
  • Collapsing
  • Noisy breathing or a congestion
  • An extra "gallop" sound in the heartbeat

Should any of the symptoms above show, the cat should be taken to the veterinarian for proper diagnosis. Certain tests may be required to properly assess the problem.

Risks of Unchecked Heart Murmurs
While heart murmurs are more of a symptom than a disease, not having the cat diagnosed can pose serious health risks should a heart disease be the culprit. Depending on the type and stage of the heart disease, the risk and medical attention varies. The cat will grow weak and lose appetite if untreated, leading to other forms of sicknesses that cause further problems. In some cases sudden death can occur too.

Interesting Fact

Heart murmurs don't exactly sound like ‘murmurs'. In fact, they may seem more like "whooshing" sounds than anything. It can also be additional extraordinary beats as opposed to the normal "Lub-dub" heart sound.

The Diagnosis of Heart Murmurs in Cats

There is a grading system to indicate the severity of a cat's heart murmurs. The system is mostly based on how loud the heart murmurs are and which part or valve area it is coming from. According to a certain criteria, heart murmurs may be graded from I to VI, with Grade I as the mildest while Grade VI the most severe. In any case, the level of loudness does not indicate the severity of the illness.

There are some cases where heart murmurs are not connected at all with any cat illness and even the loud sounds indicate a relatively mild form of disease.

Procedures for Assessment
Should the veterinarian suspect or discover clinical signs of a disease the following procedures/ examination will be given:

Chest Radiograph - an x-ray of the heart will show if there is any physical abnormalities in the cat's heart. Some diseases cause certain parts, such as the atrium, to grow progressively thicker and appear quite enlarged in an x-ray.

Echocardiography - a cardiac ultrasound scan is a painless and faster form of procedure which produces a more detailed image of the heart. This will show images of the valve and helps the veterinarian determine if there is any clogging, enlarges arteries or other abnormalities.

In some cases, an ECG or Electrocardiogram may be required, depending on the veterinarian's assessment or findings. Blood work, a urinalysis and blood pressure measurement may also be performed or required. The cat may undergo repeat examinations if the heart murmurs persist and/or other symptoms show.

Depending on the assessment and findings, the veterinarian will provide a treatment plan for the cat's heart murmurs. Most heart diseases which cause the murmurs are treatable with medicine. Surgeries are rarely needed and is not recommended for most kinds of heart diseases. The prognosis will still depend on the type of disease found in the cat and its severity. Early detection and immediate treatment will provide a higher chance of recovery and healing.

Diagnosis of Heart Murmurs in Cats - Hypertrophic Cardiomyopathy (HCM)
Diagnosis of Heart Murmurs in Cats - Hypertrophic Cardiomyopathy (HCM) | Source

Hypertrophic Cardiomyopathy (HCM)

This disease is not the most common cause of heart murmurs but is the most common type of heart disease found in cats.

Characteristics: Hypertrophic Cardiomyopathy affects young to adult cats. It may affect elderly cats but is not as commonly found in them. A cat with an HCM suffers from a thickened left ventricle. If left untreated, the left ventricle of the heart can cause clogging and enlargement of the left atrium. Most cats with HCM show little signs of it or develop symptoms that suggest problems, except for heart murmurs, and often live normal lives. Some cats do show and develop symptoms but only during the advanced stage of the disease.

Severe Cases: Advanced or severe cases of HCM causes paralysis in the hind legs of the cat. This happens because the enlarge atrium has already caused a formation of blood clot in the heart. This clot usually dislodges and get stuck in the narrow end of the aorta, the largest artery of the cat's body which is also responsible for distributing the blood supply to the hind legs.

Risks: In severe cases of HCM, the cat will show signs of pain before experiencing temporary paralysis. In some cases, the onset of paralysis is sudden, making most owners think their cat had a road accident or had been abused. Death can also suddenly occur. In some cases, treated cats with severe HCM may need maintenance drugs to prevent a possible recurrence of blood clotting.

Symptoms: Heart murmurs is the most common symptom for HCM accompanied by a loss of appetite, difficulty of breathing and pale gums. The cat may often be lethargic and the difficulty in breathing is most noticeable during exhalation.

Treatment: Certain heart drugs may be described as treatment. In some cases, a diuretic injection or treatment through tablets may be given to clear the clogged fluids in the heart.

Do you know the tests are not administered in a cat with heart murmurs indicating a possible heart disease?

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