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Familial Hypertrophic Cardiomyopathy

Last updated Sept. 11, 2018

Familial Hypertrophic Cardiomyopathy, also known as Heritable Hypertrophic Cardiomyopathy, is a condition where enlargement (hypertrophy) of the heart muscle cells occur. The enlargement or thickening of the heart muscle can be in the walls of the 4 heart chambers, or the septum that divides the chambers.


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

  • Familial Asymmetric Septal Hypertrophy
  • Hereditary Ventricular Hypertrophy
  • Heritable Hypertrophic Cardiomyopathy

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

  • Familial Hypertrophic Cardiomyopathy, also known as Heritable Hypertrophic Cardiomyopathy, is a condition where enlargement (hypertrophy) of the heart muscle cells occur. The enlargement or thickening of the heart muscle can be in the walls of the 4 heart chambers, or the septum that divides the chambers
  • The heart muscle, particularly the left ventricle, may thicken, causing the inside of the left ventricle to become smaller. This reduces the capability of left ventricle to relax sufficiently and hold enough blood. As a result, the outflow of blood is affected
  • The onset of Familial Hypertrophic Cardiomyopathy can occur at any age, though symptoms start most commonly in the 30s. A positive family history is the only risk factor known for this condition. However, certain underlying medical conditions, such as high blood pressure and uncontrolled diabetes, may exacerbate this heart condition
  • 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
  • Familial Hypertrophic Cardiomyopathy can be asymptomatic, or present with symptoms such as chest pain, shortness of breath while lying down or sleeping, fatigue, dizziness, 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 of Familial Hypertrophic Cardiomyopathy include a backflow of blood into the heart (heart valve regurgitation), aberrant heart beats (arrhythmia), sudden cardiac arrest, and dilated cardiomyopathy. Individuals with obstructive disease may develop end-stage or burn-out hypertrophic obstructive cardiomyopathy. These complications can be fatal
  • Familial Hypertrophic Cardiomyopathy may be treated with lifestyle changes, medications, non-surgical procedures, and surgical implants, depending on the severity of the condition. With early diagnosis and prompt treatment, the prognosis is generally good. However, in some individuals, a sudden cardiac arrest may the first presentation of the symptoms, 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

Familial Hypertrophic Cardiomyopathy can be classified into the following 2 types:

  • Obstructive type:
    • Blood flow blockage occurs in the left ventricle, forcing it to exertion, to pump blood to the rest of the body
    • It can also affect the mitral valve of the heart and cause blood to leak backward through the valve 
  • Non-obstructive type:
    • There is no blockage to blood flow in this condition
    • However, the pumping of blood becomes inefficient, when a part, or all of, the left ventricle becomes thicker 

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

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

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

  • Having a family history of Familial Hypertrophic Cardiomyopathy is the only major risk factor for an individual to be diagnosed with the condition
  • However, pre-existing conditions, such as uncontrolled diabetes, thyroid disease, and high blood pressure, as well as habits including heavy smoking and alcohol drinking, may exacerbate the condition

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 Familial Hypertrophic Cardiomyopathy? (Etiology)

Familial Hypertrophic Cardiomyopathy is caused by 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

What are the Signs and Symptoms of Familial Hypertrophic Cardiomyopathy?

The symptoms associated with Familial Hypertrophic 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 cardiomyopathy.

How is Familial Hypertrophic Cardiomyopathy Diagnosed?

The diagnosis of Familial Hypertrophic 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 Familial Hypertrophic Cardiomyopathy?

Familial Hypertrophic 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 hypertrophic obstructive cardiomyopathy, resulting in heart failure
  • Dilated cardiomyopathy: It results from the heart muscles becoming inefficient, such that the pumping of blood is seriously compromised

Note: The non-obstructive form can evolve into the obstructive form over the course of an individual’s lifetime.

How is Familial Hypertrophic 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, to regulate heartbeats
  • 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 Familial Hypertrophic Cardiomyopathy be Prevented?

Familial Hypertrophic Cardiomyopathy is a genetic condition, 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 Familial Hypertrophic 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 Familial Hypertrophic Cardiomyopathy? (Outcomes/Resolutions)

The prognosis of Familial Hypertrophic Cardiomyopathy depends on early diagnosis, as well as prompt and sustained treatment. The symptoms are reportedly milder in the non-obstructive type of hypertrophic cardiomyopathy

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

Additional and Relevant Useful Information for Familial Hypertrophic Cardiomyopathy:

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

http://www.dovemed.com/healthy-living/heart-center/

What are some Useful Resources for Additional Information?


References and Information Sources used for the Article:


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Reviewed and Approved by a member of the DoveMed Editorial Board
First uploaded: March 26, 2017
Last updated: Sept. 11, 2018

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