Hypertrophic cardiomyopathy is a frequent condition in the cat. It is characterized by an abnormal thickening in one or multiple areas of the cardiac muscle (especially in the left ventricle) : this abnormal thickening is called hypertrophy. It is a syndrome assembling multiple anomalies and often the causes remains undetermined. Among the possible reasons: hyperthyroidism, high blood pressure, diabetes…

Normal anatomy of the feline heart

Animation demonstrating hypertrophic cardiomyopathy in the cat

Are there any predisposed breeds?

Yes – like the Ragdool, the Main Coon, the Persian, the Birman, the Sphynx, the Norwegian, the Devon Rex…

In the Ragdolls and Main Coons, it is due to a specific genetic anomaly involving a contractile protein. In these breeds, a test is possible by tracking a DNA analysis.

What are the consequences of this thickening of the cardiac muscle?

They can vary. If the hypertrophy is light and localized, the cat may never develop any symptoms. However, if it is more severe, the cardiac ventricle may present difficulties to expand and the pressure in the heart will increase which can generate a congestive cardiac failure with accumulation of liquid in the lungs (pulmonary oedema) or around the lungs (pleural effusion).

Cardiac arrhythmias may also be present and blood clots (emboli) may be produced. These blood aggregates will circulate in the body causing various damages when they obstruct an important artery such as the iliac artery which irrigates the inferior members. This type of obstruction causes a sudden onset of paralysis. The phenomenon is also known as arterial thromboembolism.

What are the clinical signs?

Some cats are asymptomatic and do not present any modification during auscultation. Some present signs of cardiac failure that are not often specific and can vary in intensity.

The first category of cats, the ones with no symptoms, are a real challenge for the pet owner, the vet and the animal itself. Therefore, they can suffer a brutal and unpredictable cardiac incident.

Among the more progressive clinical signs, we can list fatigue, the loss of appetite, listless but also non-specific symptoms like vomits.

How to diagnose hypertrophic cardiomyopathy?

X-rays can reveal a modification of the shape of the heart. It can also reveal the presence certain complications like pleural effusions or pulmonary oedema. An electrocardiogram can also be considered if there is a suspected arrhythmia. A sonographic examination (ultrasound) or a Doppler are useful and are more and more offered. These tests allow a accurate diagnosis and a pertinent prognostic. All of the exams that contribute to diagnose this syndrome must be considered.

Video of an ultrasonographic examination in a cat with hypertrophic cardiomyopathy.

What is the treatment?

The best approach includes identifying the cause and treating it, but that is the challenge of this syndrome! The results of the various exams and tests will allow your vet to select the best treatment. Prognosis varies greatly with the underlying cause.

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