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Hypertrophic Obstructive Cardiomyopathy

Last updated Oct. 8, 2018

Approved by: Maulik P. Purohit MD, MPH

Hypertrophic Obstructive Cardiomyopathy (HOCM) is a subtype of hypertrophic cardiomyopathy, which is a condition affecting the heart muscle.

What are the other Names for this Condition? (Also known as/Synonyms)

  • Asymmetric Septal Hypertrophy
  • HOCM (Hypertrophic Obstructive Cardiomyopathy)
  • Idiopathic Hypertrophic Subaortal Stenosis

What is Hypertrophic Obstructive Cardiomyopathy? (Definition/Background Information)

  • Hypertrophic Obstructive Cardiomyopathy (HOCM) is a subtype of hypertrophic cardiomyopathy, which is a condition affecting the heart muscle
  • “Obstructive,” as the name suggests, implies that the condition interferes with the flow of blood. The term “hypertrophic” means enlargement of cells, which, in this condition, leads to the following:
    • Thickening of the heart muscle; most commonly, of the wall (septum) that divides the 4 chambers of the heart
    • Or, thickening of the heart chambers (particularly the left ventricle)
  • In this condition, the left ventricle becomes smaller in size, which reduces its capability to relax sufficiently and hold enough blood. This causes an obstruction in blood flow in the left ventricle forcing it to exertion, to pump blood to the rest of the body. Additionally, the mitral valve can also be affected, causing blood to leak backward through the valve
  • The onset of Hypertrophic Obstructive Cardiomyopathy can occur at any age, though symptoms start most commonly in the 30s. There are 2 types of HOCM:
    • Inherited Hypertrophic Obstructive Cardiomyopathy
    • Non-inherited Hypertrophic Obstructive Cardiomyopathy
  • Many of the affected individuals have a family history of the condition. Therefore, having a positive family history is a major risk factor for being diagnosed with HOCM. A few other risk factors include underlying health conditions, such as thyroid disease and high blood pressure, smoking, and a sedentary lifestyle
  • Mutations in several genes (including MYH7, MYBPC3, TNNT2, and TNNI3 genes) are known to cause the inherited form of hypertrophic cardiomyopathy. The pattern of inheritance is autosomal dominant, in which a single copy of the defective gene in each cell of an individual is sufficient to cause the condition
  • Hypertrophic Obstructive Cardiomyopathy can be asymptomatic, or present with symptoms such as chest pain, shortness of breath, coughing, and palpitations. The diagnosis of the condition may involve tests such as echocardiography (ECG), electrocardiography (EKG), stress test, and coronary catheterization. If required, a biopsy of the heart muscle may be ordered
  • Some potential complications include backflow of blood into the heart (heart valve regurgitation), aberrant heart beats (arrhythmia), sudden cardiac arrest, and development of blood clot. Individuals with obstructive disease may develop end-stage or burn-out Hypertrophic Obstructive Cardiomyopathy
  • The heart condition may be treated with lifestyle changes, medications, non-surgical procedures, and surgical implants, depending on the severity. With early diagnosis and prompt treatment, the prognosis of Hypertrophic Obstructive Cardiomyopathy is generally good. However, in some individuals, a cardiac arrest may the first presentation of HOCM, which can even be fatal
  • Currently, there are no guidelines or methods available to prevent inherited forms of hypertrophic cardiomyopathy. Nevertheless, bringing about certain lifestyle changes and treating underlying medical conditions may help avoid or reduce severity of the symptoms

Who gets Hypertrophic Obstructive Cardiomyopathy? (Age and Sex Distribution)

  • Hypertrophic Obstructive Cardiomyopathy occurs at a frequency of approximately 1:500
  • HOCM onset can occur at any age, but typically, presents in adulthood (in the 30s)
  • The condition can occur in both male and female genders
  • There is no racial or ethnic predilection noted

What are the Risk Factors for Hypertrophic Obstructive Cardiomyopathy? (Predisposing Factors)

The following are some known risk factors for Hypertrophic Obstructive Cardiomyopathy:

  • A family history of the condition, which is observed in approximately 60% of the affected individuals
  • Sudden death of a family member from cardiac arrest
  • High blood pressure
  • Thyroid disease
  • Diabetes
  • Smoking, alcoholism
  • Obesity
  • Lack of regular physical activity; leading a sedentary lifestyle

It is important to note that having a risk factor does not mean that one will get the condition. A risk factor increases one’s chances of getting a condition compared to an individual without the risk factors. Some risk factors are more important than others.

Also, not having a risk factor does not mean that an individual will not get the condition. It is always important to discuss the effect of risk factors with your healthcare provider.

What are the Causes of Hypertrophic Obstructive Cardiomyopathy? (Etiology)

The cause of Hypertrophic Obstructive Cardiomyopathy may include genetic abnormalities, which may result in mutations in the MYH7, MYBPC3, TNNT2, TNNI3, and some other unidentified genes.

  • Under normal circumstances, these genes code for proteins involved in the formation of muscle structures called sarcomeres, which help the heart muscles contract properly. The sarcomeres are composed of thick and thin muscle filaments, which work in unison by attaching and releasing in a rhythmic manner, allowing the muscles to contract and relax, respectively. This process is necessary for the heart to pump blood
  • The following are some known gene functions:
    • MYH7: It codes for cardiac β myosin heavy chain, a crucial component of thick filament
    • MYBPC3: It codes for cardiac myosin binding protein, associates with the thick filament and provides structural integrity required for contractions
    • TNNT2: It codes for cardiac troponin T, which is 1 of the 3 proteins of the troponin complex in thin filaments, required for muscle contractions and relaxations
    • TNNI3: It codes for cardiac troponin 1, also a part of the troponin complex
  • When there is a mutation in one or many genes involved in this process, it may result in altered proteins or loss of proteins in the sarcomeres, interfering with cardiac function. However, the link between compromised sarcomere function and thickening of cardiac muscles is not well understood
  • The mutations are inherited in an autosomal dominant manner. In this type of inheritance, a single copy of a defective gene in every cell of the individual is sufficient to cause disease. Typically, one inherits the condition from an affected parent
  • Spontaneous mutations can cause the condition as well; although, the exact reason and nature of these mutations is not yet well understood

Additionally, individuals with conditions, such as high blood pressure, uncontrolled diabetes, and thyroid disease, are also prone to developing HOCM. However, the cause of this heart condition originating from such factors is presently unknown.

What are the Signs and Symptoms of Hypertrophic Obstructive Cardiomyopathy?

The signs and symptoms associated with Hypertrophic Obstructive Cardiomyopathy include:

  • Chest pain
  • Dizziness, fainting
  • Shortness of breath, particularly with physical exertion (exertional dyspnea)
  • Shortness of breath, while lying down (orthopnea)
  • Shortness of breath and coughing while sleeping (nocturnal paroxysmal dyspnea)
  • Fatigue
  • Palpitations; a sensation of rapid fluttering or pounding heartbeat
  • Heart murmurs: It is an unusual sound heard during the heartbeat. This can be an extra beat or whooshing/swishing sound, and may be faint or loud
  • Swelling of ankles, legs, abdomen, or veins in the neck

The symptoms may be any or many of the above. There may be variations in degree of severity from one individual to another.

Note: In some cases, the condition may be completely asymptomatic and sudden fainting may be the first presentation of Hypertrophic Obstructive Cardiomyopathy.

How is Hypertrophic Obstructive Cardiomyopathy Diagnosed?

The diagnosis of Hypertrophic Obstructive Cardiomyopathy is made with the help of information gathered from the following tests and procedures:

  • A thorough physical examination and an assessment of symptoms
  • Evaluation of personal and family medical history
  • Chest X-ray to check for heart size, contour, and fluid build-up in lungs
  • Electrocardiogram (EKG) to check the heart’s electrical activity
  • Echocardiography (ECG or echo) uses sound waves to create a moving picture of the heart. This helps to check the size, shape, and pumping function of the heart
  • Stress test: This test places stress on the heart by making it work harder and beat faster to determine, if the cardiac muscles can cope with the increased workload
  • Cardiac catheterization: To check for pressure and blood flow in the heart’s chambers. It is often coupled with coronary angiography, in which a harmless dye is injected into the coronary arties and with the help of an X-ray, blood flow through heart and blood vessels can be observed
  • Myocardial biopsy: A piece of the heart is removed and the cells are investigated for changes that may suggest hypertrophic cardiomyopathy
  • Genetic testing to seek confirmation of the diagnosis. This may be recommended for the whole family, which can help understand if the condition is inherited

Many clinical conditions may have similar signs and symptoms. Your healthcare provider may perform additional tests to rule out other clinical conditions to arrive at a definitive diagnosis.

What are the possible Complications of Hypertrophic Obstructive Cardiomyopathy?

Hypertrophic Obstructive Cardiomyopathy can lead to following complications:

  • Heart valve regurgitation: It causes the heart to pump ineffectively, such that blood flows back into the heart
  • Arrhythmias: Abnormal heart rhythm, which can be triggered by physical exertion
  • Sudden cardiac arrest (which can be unexpected)
  • Embolism: Development of blood clots in the heart which may get into the bloodstream and obstruct blood supply to many important organs
  • Edema: Fluid buildup in the lungs, abdomen, legs, and feet; all consequences of ineffective heart pumping
  • End stage HOCM, resulting in heart failure
  • Dilated cardiomyopathy: It results from the heart muscles becoming inefficient, such that the pumping of blood is seriously compromised

How is Hypertrophic Obstructive Cardiomyopathy Treated?

The treatment options for Hypertrophic Obstructive Cardiomyopathy may include the following:

  • Lifestyle changes:
    • Adhering to a healthy diet that includes fresh fruits, vegetables, whole grains, fish and dairy products
    • Engaging in routine physical activity
    • Smoking cessation
    • Losing excess weight
    • Avoiding alcohol and illicit drugs
    • Getting enough sleep
    • Avoiding or reducing of stress
    • Seeking treatment for underlying conditions (such as diabetes, high blood pressure)
  • Beta blockers and calcium channel blockers, generally the first choice of medicines to treat cardiomyopathies
  • Other prescription medications may help in:
    • Regulating high blood pressure levels
    • Slow heart rate
    • Maintain normal heart beat rhythm
    • Balance electrolytes in the body; electrolytes are minerals that help in the proper functioning of muscles and nerve tissues
    • Removing excess fluid and sodium
    • Preventing blood clot formation (through anti-coagulants or blood thinners)
    • Reducing inflammation 
  • Non-surgical procedures, such as alcohol septal ablation, in which:
    • Ethanol (a type of alcohol) is injected into a small artery
    • The alcohol kills cells in the tissue, to shrink the heart muscle to a more ‘normal’ size
    • This improves blood flow through the ventricles, which in turn improves the symptoms

Surgical procedures:

  • Septal myectomy:
    • It is a type of open-heart surgery that is typically used for Obstructive Hypertrophic Cardiomyopathy with severe symptoms
    • The procedure is usually recommended for young patients with poor response to medicines
    • It helps in improving blood pumping by removing part of the thickened heart muscle
  • Surgically-implanted devices such as implantable cardioverter defibrillator (ICD):
    • It is a small device implanted in the chest or abdomen and connected to the heart via wires
    • The device helps control life-threatening arrhythmias that can lead to sudden cardiac arrest
  • In a small percentage of the affected individuals, heart transplantation may be necessary

How can Hypertrophic Obstructive Cardiomyopathy be Prevented?

Hypertrophic Obstructive Cardiomyopathy is a genetic condition in a majority of the affected individuals, and therefore, there are no guidelines or specific methods for preventing the condition from developing.

  • Genetic testing of the expecting parents (and related family members) and prenatal diagnosis (molecular testing of the fetus during pregnancy) may help in understanding the risks better during pregnancy
  • If there is a family history of the condition, then genetic counseling will help assess risks, before planning for a child
  • Active research is currently being performed to explore the possibilities for treatment and prevention of inherited and acquired genetic disorders such as Hypertrophic Obstructive Cardiomyopathy
  • Regular medical screening at periodic intervals with tests and physical examinations are strongly recommended
  • Some lifestyle changes, such as following a healthy diet, quitting cigarettes, reducing alcohol drinking, getting regular exercise and reducing stress, may help prevent the severity and complications from the condition
  • In high-risk individuals, an implantable cardioverter defibrillator may help prevent sudden cardiac arrest, a potential complication of hypertrophic cardiomyopathy

What is the Prognosis of Hypertrophic Obstructive Cardiomyopathy? (Outcomes/Resolutions)

The prognosis of Hypertrophic Obstructive Cardiomyopathy typically depends on early diagnosis, as well as timely and appropriate treatment.

  • Treatment can help prevent worsening of the condition, control symptoms, and reduce complications, leading to better outcomes
  • Without treatment, the symptoms can worsen resulting in severe complications
  • In some cases, sudden cardiac arrest even at first presentation of the disease, may be fatal 

Additional and Relevant Useful Information for Hypertrophic Obstructive Cardiomyopathy:

Please visit our Heart & Vascular Health Center for more physician-approved health information:


What are some Useful Resources for Additional Information?

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Reviewed and Approved by a member of the DoveMed Editorial Board
First uploaded: March 26, 2017
Last updated: Oct. 8, 2018