Hypertrophic cardiomyopathy

Medical quality assurance by Dr. Albrecht Nonnenmacher, MD at May 26, 2016
StartDiseasesHypertrophic cardiomyopathy

Hypertrophic cardiomyopathy, also known as HCM, is a form of heart disease in which the heart muscle hypertrophies or becomes abnormally thick. HCM affects anywhere from 600,000 to 1.5 million people in the United States. Many of those with HCM suffer only minor, if any, symptoms; however, symptoms can become more pronounced as the condition progresses.

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Definition & Facts

Hypertrophic cardiomyopathy most often affects the septum of the heart. This is the muscular wall that divides the two sides of the heart. A thickened septum can cause an outflow obstruction, which means that the blood is not able to flow from the left ventricle (heart) to the aorta. As a result, the ventricles are forced to pump harder to compensate for the reduced blood flow.

It is also common for the left ventricle to become very stiff. This means that the ventricle does not relax completely between contractions, so the chamber is unable to fill up with as much blood. This results in less oxygen-rich blood being delivered throughout the body. It can also increase the pressure inside the heart.

Many individuals with HCM also have a leaky mitral valve, which allows blood to flow back into the left atrium. HCM can also cause cellular changes to the heart muscle. When examined under a microscope, the cells often appear irregular and disorganized instead of parallel and orderly. This can affect the way electrical signals travel through the heart and can lead to dangerously abnormal heart rhythms.

Symptoms & Complaints

Many of the symptoms of hypertrophic cardiomyopathy are associated with the presence of an abnormal heart rhythm or heart failure, including:

Most individuals with HCM are able to live normal lives with no serious complications; however, the condition does pose a risk of other significant health problems. Abnormal heart rhythms can increase the risk of blood clots that can potentially cause a stroke. Arrhythmias affecting the ventricles can even result in sudden cardiac death. Patients can also experience heart failure if the heart muscle thickens to the point that it can no longer pump enough blood to meets the body’s demands. 

Causes

In most cases, hypertrophic cardiomyopathy is inherited. A particular genetic mutation can cause the heart muscle to thicken or cause the fibers of the heart muscle to have an abnormal arrangement called myocardial fiber disarray. Individuals with parents with the condition have a 50 percent chance of being born with the genetic mutation that causes HCM; however, some people born with the genetic mutation never go on to develop the disease. In rare instances, HCM may develop as the result of high blood pressure or even age. In some instances, a cause can never be identified. 

Diagnosis & Tests

To diagnose hypertrophic cardiomyopathy, the doctor will start by reviewing the patient’s symptoms, as well as their medical history and family history. Additional tests may also be ordered to examine the structure and electrical activity of the heart, including:

  • An echocardiogram that uses ultrasound beams to provide images of the heart in action.
  • An electrocardiogram, or ECG, that measures the heart’s electrical impulses.
  • A treadmill test to assess exercise tolerance and to determine if exertion triggers any heart arrhythmias.
  • A Holter monitor that provides a record of the heart’s activity over the period of a couple of days.
  • A cardiac MRI that uses radio waves and magnetic fields to create a detailed image of the heart. 

A doctor may recommend HCM screening if an individual has a first-degree relative with HCM. This may include genetic testing or periodic echocardiography. It is important to note that genetic testing is only worthwhile for the 50 to 60 percent of individuals with the specific gene mutation.

Treatment & Therapy

The treatment for hypertrophic cardiomyopathy depends on a variety of factors, including the current level of heart function, whether the patient is experiencing any arrhythmias, and whether there is an obstruction affecting the flow of blood from the heart. Medications, such as beta blockers, calcium channel blockers, and antiarrhythmic agents, may be used to relax the heart and slow the heart rate. Individuals with HCM who also have atrial fibrillation may also be prescribed blood thinners to reduce the risk of blood clots.

An open-heart procedure called a septal myectomy may be used to remove a portion of the thickened septum and repair a leaky mitral valve. This helps improve blood flow and can reduce mitral valve regurgitation. Another common procedure used to treat HCM is a septal ablation. This involves destroying a small portion of the affected heart muscle by injecting it with alcohol through a long, thin catheter inserted through an artery.

Patients with HCM who experience ventricular arrhythmias typically undergo a procedure to implant a cardioverter-defibrillator. The device is inserted under the skin of the chest and delivers a controlled shock to the heart if it detects an abnormal rhythm. 

Prevention & Prophylaxis

Because hypertrophic cardiomyopathy is typically inherited, there is no way to prevent the disease. On the other hand, lifestyle measures can improve the patient’s quality of life and reduce the risk of complications:

  • Individuals with HCM may be able to engage in low to moderate-intensity physical activity, but they should avoid competitive sports.
  • It is important to eat a balanced diet and maintain a healthy weight to reduce the risk of other health conditions.
  • People with HCM should avoid drinking excessive alcohol since this can trigger an abnormal heart rhythm. 
  • Individuals with the condition should take all medications as prescribed and follow-up with their doctor or cardiologist as directed.