Home » Diseases » In cats » Hypertrophic Cardiomyopathy (Heart Disease Due to Thickening of the Heart Muscle)

Hypertrophic Cardiomyopathy (Heart Disease Due to Thickening of the Heart Muscle) in cats

Occurrence: common
Location of illness: Chest

Author: Dr. med. vet. Gisa Löwe | Last modified: 17.02.2026

When to visit the vet?

Urgent see a veterinarian within 24 hours

If the condition worsens / symptoms persist, consult a veterinarian.

Definition

Hypertrophic cardiomyopathy (HCM) is a condition in which a cat’s heart muscle thickens, which can impair the heart’s ability to pump blood efficiently. This thickening can lead to a range of heart problems and is the most common heart disease in cats.

The most important facts at a glance

Hypertrophic cardiomyopathy (HCM) in cats is a heart disease in which the walls of the left ventricleA ventricle is one of the two lower chambers of the heart that pump blood into the arteries. The right ventricle pumps blood to the lungs, while the left ventricle pumps blood throughout the body. are thickened, impairing the elasticity of the heart muscle and the heart’s filling. This can lead to an inadequate blood supply to the body and cause symptoms such as loss of appetite, weakness, respiratoryRespiratory refers to breathing or the process of breathing. Respiratory diseases affect the respiratory tract and can impair the ability to breathe effectively. distress, and cardiac arrhythmiaAn arrhythmia is a heart rhythm disorder in which the heart beats irregularly, either too fast (tachycardia), too slow (bradycardia), or with an irregular pattern. Arrhythmias can be harmless or a sign of serious heart problems.. The causes of HCM are not fully understood, but genetic factors play an important role, especially in breeds such as the Maine Coon and Ragdoll. Other factors such as high blood pressure and hyperthyroidism can also increase the risk.

DiagnosisA diagnosis is the identification of a disease or condition by its symptoms and/or results from diagnostic tests. It is the first step in the management and treatment of patients. is made through clinical examinations, cardiac ultrasoundUltrasound refers to sound waves that are above the hearing threshold of the human ear. In medicine, ultrasound is used for diagnostic imaging procedures to visualize internal organs, tissues, and blood flow., ECG, and blood tests, while treatment aims to relieve symptoms and slow disease progressionProgression refers to the advancement or worsening of a disease over time. It describes an increase in the severity or extent of the disease symptoms., often with medications and diureticsDiuretics are medications that increase urine production in the kidneys to rid the body of excess salt and water. They are often used to treat high blood pressure, heart failure, and certain types of edema.. Early diagnosisA diagnosis is the identification of a disease or condition by its symptoms and/or results from diagnostic tests. It is the first step in the management and treatment of patients. and regular veterinary monitoring are crucial for the prognosisThe prognosis is the prediction of the likely course and outcome of a disease based on the general state of health, the nature of the disease, and the response to treatment. It can provide information on how a disease is expected to develop.. Preventive measures include responsible breeding and a healthy lifestyle. Research focuses on genetic foundations, improved diagnostics, and new treatment methods to improve the quality of life of affected cats.

Causes

Hypertrophic cardiomyopathy in cats is characterized by thickening of the walls of the heart’s left ventricleA ventricle is one of the two lower chambers of the heart that pump blood into the arteries. The right ventricle pumps blood to the lungs, while the left ventricle pumps blood throughout the body.. This thickening can reduce the elasticity of the heart muscle, which impairs the heart’s filling during diastoleDiastole is the phase of the cardiac cycle in which the ventricles relax and fill with blood after contracting and pumping blood into the arteries during the previous phase, systole. (the relaxation phase of the cardiac cycle). As a result, the body may receive less blood, which can triggerA trigger is a stimulus that elicits a specific reaction or state. In veterinary medicine, this can refer to emotional responses, such as fear or aggression, or medical conditions, such as seizures in dogs and cats. a wide range of symptoms.

The exact causes of HCM are not fully understood, but genetic factors play a significant role. Certain cat breeds, such as the Maine Coon, Ragdoll, and British Shorthair, are known to have a genetic predispositionA predisposition is an innate inclination or susceptibility of an organism to certain diseases or conditions. In dogs and cats, there may be a genetic predisposition to certain conditions such as hip dysplasia or certain heart diseases. to developing this condition. Studies have identified specific genetic mutations that may be associated with HCM.

Hormonal influences and other systemic diseases may also contribute to the development of HCM. For example, high blood pressure or hyperthyroidism (an overactive thyroid) can increase the risk of developing a heart muscle disease. Environmental factors and diet may also play a role, although this has been studied less extensively.

Symptoms

Very common symptoms:

Common symptoms:

Rare symptoms:

Cats with hypertrophic cardiomyopathy often show symptoms only at an advanced stage, as cats tend to hide signs of illness. The most common symptoms include respiratoryRespiratory refers to breathing or the process of breathing. Respiratory diseases affect the respiratory tract and can impair the ability to breathe effectively. distress caused by fluid buildup in the lungs or chest cavity. Affected cats may also have an increased breathing rate or shortness of breath.

Another symptom is lethargy or reduced activity, as cats have less energy due to decreased heart performance. In some cases, fainting episodes or collapse can occur, especially after physical exertion. Loss of appetite and weight loss are also possible signs.

A particularly serious symptom is the development of thromboembolismThromboembolism is the blockage of a blood vessel by a blood clot (thrombus) that has formed in one place in the circulatory system and then moved to another location. This can lead to serious complications, such as a stroke or pulmonary embolism., in which blood clots form in blood vessels leaving the heart. This can lead to sudden paralysisParalysis is the complete loss of muscle activity in one or more areas of the body, which can lead to immobility and loss of sensation. Paralysis can be caused by injuries, illnesses, or disorders of the nervous system., especially of the hind legs, and is often very painful.

Diagnosis

The diagnosisA diagnosis is the identification of a disease or condition by its symptoms and/or results from diagnostic tests. It is the first step in the management and treatment of patients. of HCM usually begins with a thorough clinical examination and a careful medical historyThe medical history is the systematic collection of a patient's medical history through questioning. It includes information about previous illnesses, treatments, allergies, and lifestyle habits.. The veterinarian will look for possible symptoms and listen to the heart with a stethoscopeA stethoscope is a medical instrument used for auscultation, or listening to body sounds, such as heartbeats and lung sounds. It is a fundamental tool in medical diagnostics. to detect abnormal sounds such as heart murmurs or cardiac arrhythmiaAn arrhythmia is a heart rhythm disorder in which the heart beats irregularly, either too fast (tachycardia), too slow (bradycardia), or with an irregular pattern. Arrhythmias can be harmless or a sign of serious heart problems..

An important diagnostic tool is a cardiac ultrasoundUltrasound refers to sound waves that are above the hearing threshold of the human ear. In medicine, ultrasound is used for diagnostic imaging procedures to visualize internal organs, tissues, and blood flow. (echocardiogram), which provides a visual representation of the heart and can assess thickening of the heart walls as well as the movement of the heart valves. This examination is crucial to confirm an HCM diagnosisA diagnosis is the identification of a disease or condition by its symptoms and/or results from diagnostic tests. It is the first step in the management and treatment of patients. and determine the severity of the condition.

In addition, chest X-rays may be taken to assess the size and shape of the heart and to determine whether there are signs of fluid buildup in the lungs. An electrocardiogramSee ECG. (ECG) may also be performed to detect cardiac arrhythmiaAn arrhythmia is a heart rhythm disorder in which the heart beats irregularly, either too fast (tachycardia), too slow (bradycardia), or with an irregular pattern. Arrhythmias can be harmless or a sign of serious heart problems.. Blood tests help rule out other underlying conditions that could affect the heart disease.

Therapy

There is no cure for HCM, but treatment aims to relieve symptoms and slow disease progressionProgression refers to the advancement or worsening of a disease over time. It describes an increase in the severity or extent of the disease symptoms.. Medications that slow the heart rate and improve heart function may be prescribed to reduce strain on the heart. DiureticsDiuretics are medications that increase urine production in the kidneys to rid the body of excess salt and water. They are often used to treat high blood pressure, heart failure, and certain types of edema. can help remove excess fluid from the body and relieve respiratoryRespiratory refers to breathing or the process of breathing. Respiratory diseases affect the respiratory tract and can impair the ability to breathe effectively. problems.

In some cases, anticoagulantsAnticoagulants are medications that slow down or inhibit blood coagulation. They are used to prevent the formation of blood clots and are used in dogs and cats with certain heart conditions or coagulation disorders. may be used to prevent blood clots from forming, especially when the risk of thromboembolismThromboembolism is the blockage of a blood vessel by a blood clot (thrombus) that has formed in one place in the circulatory system and then moved to another location. This can lead to serious complications, such as a stroke or pulmonary embolism. is high. Regular monitoring by the veterinarian is important to assess how well treatment is working and to make adjustments if the animal’s condition changes.

Some cats may need specialized dietary management aimed at controlling blood pressure and supporting heart health. In severe cases, inpatient treatment may be necessary to manage acuteAcute refers to a condition that occurs suddenly and is usually of short duration. In a medical context, it describes symptoms or illnesses that can quickly become serious and require immediate attention. symptoms.

Prognosis and follow-up care

The prognosis for cats with HCM varies widely and depends on the severity of the disease and the response to treatment. Some cats can live with the disease for many years, especially if it is diagnosed early and treated effectively. Other cats may develop rapidly progressing symptoms that are harder to control.

Complications such as thromboembolismThromboembolism is the blockage of a blood vessel by a blood clot (thrombus) that has formed in one place in the circulatory system and then moved to another location. This can lead to serious complications, such as a stroke or pulmonary embolism. or heart failure can significantly worsen the prognosisThe prognosis is the prediction of the likely course and outcome of a disease based on the general state of health, the nature of the disease, and the response to treatment. It can provide information on how a disease is expected to develop.. Cats that show signs of heart failure or blood clots generally have a poorer prognosisThe prognosis is the prediction of the likely course and outcome of a disease based on the general state of health, the nature of the disease, and the response to treatment. It can provide information on how a disease is expected to develop..

Regular veterinary examinations and close monitoring of heart health are crucial to improving the quality of life of affected cats and detecting complications early.

Prevention

PreventionPrevention includes measures taken to prevent diseases or injuries. In veterinary medicine, this includes vaccinations, parasite control, and health monitoring. of hypertrophic cardiomyopathy (HCM) in cats can be challenging because it is often a genetic disease. However, there are some measures that can minimize the risk. One of the most important preventionPrevention includes measures taken to prevent diseases or injuries. In veterinary medicine, this includes vaccinations, parasite control, and health monitoring. strategies is responsible breeding. Cats that carry genetic mutations associated with HCM should not be used for breeding. Regular veterinary examinations are essential to detect early signs of the disease and act accordingly.

A healthy lifestyle can also play a role. This includes a balanced diet that supports the cat’s ideal weight, as overweight can put additional strain on the heart. Regular exercise helps keep the cat’s cardiovascular system in good condition. Since stressStress refers to the state of an organism reacting to external stimuli or demands. In veterinary medicine, stress can have physical or psychological effects on animals, impacting their health and well-being. can also have a negative impact on heart health, it is important to create a calm and stable living environment for the cat. Avoiding known stressors and providing safe retreats can help improve the cat’s well-being. Regular heart scans in breeds known to be at risk can also help detect HCM early and take appropriate action.

Outlook on current research

Hypertrophic cardiomyopathy (HCM) is the most common heart disease in cats and is a major area of research in veterinary medicine. Scientists are working intensively to understand the genetic basis of this condition, as HCM often has an inherited component. Various cat breeds, such as the Maine Coon and Ragdoll, show a higher prevalence, suggesting a genetic predispositionA predisposition is an innate inclination or susceptibility of an organism to certain diseases or conditions. In dogs and cats, there may be a genetic predisposition to certain conditions such as hip dysplasia or certain heart diseases.. Researchers use genetic tests to identify specific mutations associated with HCM and develop breeding strategies to reduce prevalence.

Another important research area is the improvement of diagnostic methods. Currently, HCM is often diagnosed through cardiac ultrasound examinations to visualize thickening of the heart muscle. Researchers are investigating the effectiveness and accuracy of new imaging techniques and biomarkers that could help detect HCM earlier and more precisely. Work is also underway to develop non-invasive methods that minimize stressStress refers to the state of an organism reacting to external stimuli or demands. In veterinary medicine, stress can have physical or psychological effects on animals, impacting their health and well-being. for the cat during diagnosisA diagnosis is the identification of a disease or condition by its symptoms and/or results from diagnostic tests. It is the first step in the management and treatment of patients..

Treatment of hypertrophic cardiomyopathy is also a central research topic. Since there is currently no cure for HCM, studies focus on improving the quality of life and life expectancy of affected cats. Researchers are examining different medications and combinations to relieve symptoms and support heart function. Developing new drugs that specifically target the underlying molecular mechanisms of HCM is a promising approach.

Another exciting area of research is the role of diet and lifestyle in the development and progressionProgression refers to the advancement or worsening of a disease over time. It describes an increase in the severity or extent of the disease symptoms. of HCM. Studies are investigating whether certain nutrients or diets affect heart health and whether lifestyle changes, such as stressStress refers to the state of an organism reacting to external stimuli or demands. In veterinary medicine, stress can have physical or psychological effects on animals, impacting their health and well-being. reduction and controlled exercise, can have positive effects on the course of the disease. These findings could lead to new recommendations for managing HCM.

Finally, the role of environmental factors in the development and course of HCM is also being studied. Researchers are trying to understand how environmental stressStress refers to the state of an organism reacting to external stimuli or demands. In veterinary medicine, stress can have physical or psychological effects on animals, impacting their health and well-being., infections, or other health problems can influence the risk or severity of the disease. Findings from these studies could help develop preventionPrevention includes measures taken to prevent diseases or injuries. In veterinary medicine, this includes vaccinations, parasite control, and health monitoring. measures that reduce the risk of HCM in genetically predisposed cats.

Frequently asked questions (FAQs)

What is hypertrophic cardiomyopathy (HCM) in cats? Hypertrophic cardiomyopathy (HCM) is a heart disease in which the heart muscle, especially the left ventricleA ventricle is one of the two lower chambers of the heart that pump blood into the arteries. The right ventricle pumps blood to the lungs, while the left ventricle pumps blood throughout the body., becomes thickened. This can impair heart function and lead to heart failure.
Which cats are most often affected by HCM? HCM can occur in any cat breed, but it is more common in certain breeds such as the Maine Coon and the Ragdoll. Genetic factors are thought to play a role.
How is HCM diagnosed in cats? DiagnosisA diagnosis is the identification of a disease or condition by its symptoms and/or results from diagnostic tests. It is the first step in the management and treatment of patients. is usually made by an ultrasoundUltrasound refers to sound waves that are above the hearing threshold of the human ear. In medicine, ultrasound is used for diagnostic imaging procedures to visualize internal organs, tissues, and blood flow. examination of the heart, which can make thickening of the heart muscle visible. Additional tests such as X-rays and ECGs may also be performed.
Can HCM be cured in cats? There is currently no cure for HCM. Treatment aims to relieve symptoms and improve quality of life, often with medications that support heart function.
What symptoms may indicate HCM in cats? Symptoms can include shortness of breath, cough, reduced activity, loss of appetite, and in severe cases sudden collapse or death. Cats often show no symptoms until the disease is advanced.
Is HCM hereditary in cats? Yes, HCM has a genetic component. In some breeds, specific genetic mutations have been identified that increase the risk. Breeders are working to minimize these mutations through targeted breeding.
What treatment options are available for cats with HCM? Treatment often includes medications to support heart function and control symptoms. DiureticsDiuretics are medications that increase urine production in the kidneys to rid the body of excess salt and water. They are often used to treat high blood pressure, heart failure, and certain types of edema., beta blockerBeta blockers are a class of medications used to lower blood pressure, treat cardiac arrhythmia, and reduce the heart's workload. They work by reducing the effect of epinephrine on the heart., and ACE inhibitorACE inhibitors are medications that inhibit angiotensin-converting enzyme, thereby lowering blood pressure. They also have a protective effect on the kidneys. They are used in dogs and cats to treat heart disease, high blood pressure, and certain kidney diseases. are commonly used medications. The veterinarian will determine the best therapyTherapy refers to the treatment of diseases or disorders with the aim of alleviating symptoms, promoting healing, or improving quality of life. Therapies can be medicinal, surgical, or through other medical interventions. based on the individual case.
Can diet and lifestyle influence the risk of HCM? There is evidence that a balanced diet and a low-stress lifestyle can have a positive effect on heart health. Regular veterinary check-ups are also important to monitor disease progressionProgression refers to the advancement or worsening of a disease over time. It describes an increase in the severity or extent of the disease symptoms..
How often should a cat with HCM be examined by a veterinarian? Cats with HCM should have regular check-ups with the veterinarian, usually every 6 to 12 months, to monitor the progressionProgression refers to the advancement or worsening of a disease over time. It describes an increase in the severity or extent of the disease symptoms. of the disease and adjust treatment.
Are there preventive measures to prevent HCM in cats? While genetic factors cannot be changed, regular veterinary examinations and a healthy lifestyle can help maintain heart health and detect early signs of the disease.

Frequently asked questions (FAQs)

1. What is hypertrophic cardiomyopathy (HCM) in cats?

Hypertrophic cardiomyopathy (HCM) is a heart disease in which the heart muscle, especially the left ventricle, becomes thickened. This can impair heart function and lead to heart failure.

2. Which cats are most often affected by HCM?

HCM can occur in any cat breed, but it is more common in certain breeds such as the Maine Coon and the Ragdoll. Genetic factors are thought to play a role.

3. How is HCM diagnosed in cats?

Diagnosis is usually made by an ultrasound examination of the heart, which can make thickening of the heart muscle visible. Additional tests such as X-rays and ECGs may also be performed.

4. Can HCM be cured in cats?

There is currently no cure for HCM. Treatment aims to relieve symptoms and improve quality of life, often with medications that support heart function.

5. What symptoms may indicate HCM in cats?

Symptoms can include shortness of breath, cough, reduced activity, loss of appetite, and in severe cases sudden collapse or death. Cats often show no symptoms until the disease is advanced.

6. Is HCM hereditary in cats?

Yes, HCM has a genetic component. In some breeds, specific genetic mutations have been identified that increase the risk. Breeders are working to minimize these mutations through targeted breeding.

7. What treatment options are available for cats with HCM?

Treatment often includes medications to support heart function and control symptoms. Diuretics, beta blocker, and ACE inhibitor are commonly used medications. The veterinarian will determine the best therapy based on the individual case.

8. Can diet and lifestyle influence the risk of HCM?

There is evidence that a balanced diet and a low-stress lifestyle can have a positive effect on heart health. Regular veterinary check-ups are also important to monitor disease progression.

9. How often should a cat with HCM be examined by a veterinarian?

Cats with HCM should have regular check-ups with the veterinarian, usually every 6 to 12 months, to monitor the progression of the disease and adjust treatment.

10. Are there preventive measures to prevent HCM in cats?

While genetic factors cannot be changed, regular veterinary examinations and a healthy lifestyle can help maintain heart health and detect early signs of the disease.