Hypertrophic Cardiomyopathy                              (HCM)                                                     

HCM is a disease that causes thickening of the heart muscle resulting in poor relaxing and filling ability.

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As the heart’s pumping chamber (ventricle) becomes progressively thicker, less blood can enter the chamber; thus, less blood is ejected out to the body.

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The cause of HCM is unknown, although certain breeds of cats appear to be predisposed. Middle-aged male cats may be more commonly affected.

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Sometimes heart muscle thickening similar to HCM can develop secondary to other disorders such as hyperthyroidism (elevated thyroid hormone) and systemic hypertension

(elevated blood pressure).

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Blood pressure measurement and, in cats over five years of age,

a blood thyroid hormone test should be done to exclude these secondary causes when cardiac hypertrophy (thickening) is diagnosed.

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Some pets show no sign of illness, especially early in the disease. In other cases, signs of left-sided congestive heart failure (fluid accumulation in the lung) may occur.

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These signs include lethargy, decreased activity level, rapid and/or labored breathing and possibly open mouth breathing with excitement or exercise.

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Sometimes left and right-sided congestive heart failure develop with fluid accumulation inside the chest or abdominal cavity causing greater respiratory (breathing) effort and abdominal distention.

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Once fluid accumulations have occurred, clinical heart failure is present and aggressive medical therapy should be sought.

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Other signs of this disease can include sudden weakness, collapsing episodes, and unfortunately even sudden death due to disturbances in heart rhythm.

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In some cats with a very large heart chamber (i.e. left atrium) a blood clot may form and if it enters the circulation may cause weakness or paralysis (usually of the rear legs).

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If this occurs, contact your veterinarian right away to determine if complications related to heart disease (or another disease)

are present.

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