What Is Hypertrophic Cardiomyopathy?

Hypertrophic cardiomyopathy (HCM) is a complex type of heart disease that affects the heart muscle marked by thickening of the heart muscle, left ventricular stiffness, mitral valve changes and cellular changes.

The normal heart 

Normal Heart

• The heart is a pear-shaped organ, about the size of your clenched fist, located underneath your breast bone.
• The walls of your heart are made of muscle (called the myocardium).
• The heart is divided into right and left halves by a muscular wall, called the septum.
• The mitral and tricuspid valves lie between the top chambers (atria) and bottom chambers (ventricles).
• The aortic and pulmonic valves lie between the ventricles and the blood vessels leading out of the heart.
• The heart is responsible for pumping blood throughout your body.

 

In Hypertrophic cardiomyopathy (HCM), thickening of the heart muscle (myocardium) occurs most commonly at the septum, just below the aortic valve.

Hypertrophic Cardiomyopathy

The septum is the muscular wall that separates the left and right side of the heart. Problems occur when the septum between the heart's lower chambers or ventricles is thickened.

The thickened septum may cause a narrowing that can block or reduce the blood flow from the left ventricle to the aorta - a condition called "outflow tract obstruction."

The ventricles must pump much harder to overcome the narrowing or blockage.

• This type of hypertrophic cardiomyopathy may be called:
  
  • Hypertrophic Cardiomyopathy (HCM)
  • Hypertrophic obstructive cardiomyopathy (HOCM)
  • Idiopathic hypertrophic subaortic stenosis (IHSS)

HCM may also cause thickening in other parts of the heart muscle, such as the bottom of the heart called the apex, right ventricle, or throughout the entire left ventricle.

Left ventricle stiffness occurs as a result of the thickened septum. The left ventricle also is unable to normally relax and fill with blood. The stiffness in the left ventricle causes pressure to increase inside the heart.

Mitral valve changes: When the outflow tract is narrowed, blood rushes through the passageway toward the aortic valve (like a tight garden hose nozzle), dragging the leaflets of the mitral valve with it.

The mitral valve normally functions to keep blood flowing in one direction from the left atrium (upper heart chamber) to the left ventricle.  However, the increased force of blood pulls the valve open and may cause blood to leak backward (called regurgitation) into the left atrium.
 
Cellular changes, or changes in the cells of the heart muscle cells occur with HCM. Through a microscope, the cells appear disorganized and irregular (called "disarray") instead of being organized and parallel.

This disarray may impact the electrical signals traveling through the heart and contribute to ventricular arrhythmia (a type of abnormal heart rhythm).

Who is affected by hypertrophic cardiomyopathy?

• HCM affects an estimated 600,000 to 1.5 million Americans, or one in 500 people. It is more prevalent than multiple sclerosis, which affects one in 700 people.

• HCM is the most common cause of sudden cardiac death in people under age 30. HDCM may be best known for its role in cardiac arrest and subsequent death in some young professional athletes.

What causes HCM?

HCM can be:

•  Inherited
  o HCM may be inherited, caused by an abnormality in the gene that codes the characteristics for the heart muscle.
  o When the gene defect is present, the type of HCM that develops varies greatly within the family.
  o In addition, some people who have the HCM gene may never develop the disease.
• Acquired
  o HCM my be acquired, the result of high blood pressure or aging.
• Unknown
  o Often, the cause of HCM is unknown.

Because the cause of HCM varies, it is frequently difficult to identify a high-risk population.

What are the symptoms of HCM?

Many people with HCM have no symptoms or only minor symptoms, and live a normal life. Other people develop symptoms, which progress and worsen as the heart function worsens.

Symptoms can occur at any age and may include:

• Chest pain or pressure that usually occurs with exercise or physical activity, but also may occur with rest or after meals.
• Shortness of breath (dyspnea) and fatigue, especially with exertion. These symptoms are more common in adults with HCM and are most likely caused by backup of pressure in the left atrium and to the lungs.
• Syncope (fainting or passing out) affects about 15 to 25 percent of HCM patients. Syncope with HCM may be caused by irregular heart rhythms, abnormal responses of the blood vessels during exercise, or no cause may be found.
• Palpitations (fluttering in the chest) due to abnormal heart rhythms (arrhythmias), such as atrial fibrillation or ventricular tachycardia. Atrial fibrillation occurs in about 25 percent of those with HCM, and increases risk for blood clots and heart failure.
• Sudden death occurs in a small number of patients with HCM.

How is HCM diagnosed?

The diagnosis of HCM is based on:

• Medical history : Your doctor will ask you many questions about your symptoms and family history.

• Physical exam : Your doctor will listen to your heart and lungs. Patients with severe hypertrophic obstructive cardiomyopathy (HOCM, or outflow tract obstruction) may have a heart murmur.

• Tests: Echocardiogram is the most common test used to diagnose HCM, as the characteristic thickening of the heart walls is usually visible on the echo. Other tests may include blood tests, electrocardiogram, chest x-ray, echocardiogram, exercise stress test, cardiac catheterization and magnetic resonance imaging (MRI). Click here to learn more about these diagnostic tests and procedures

How is hypertrophic cardiomyopathy treated?

The type of treatment prescribed depends on:

• Whether there is narrowing in the out-flow tract (the path blood travels to leave the heart)
• How the heart is functioning
• Patient's symptoms
• The age and activity level of the patient
• The presence of arrhythmias

Treatment is aimed at preventing symptoms and complications and includes risk identification and regular follow-up, lifestyle changes, medications and procedures as needed.

Risk Identification

It is important to identify the small number of patients with HCM who are at higher risk for sudden cardiac death, so preventive measures can be taken. People with HCM who have a higher risk for sudden death include:

• Those who have family members who had sudden cardiac death
• Young patients with several episodes of syncope  (fainting)
• Those who have an abnormal blood pressure response with exercise
• Adults who have a history of arrhythmia  with fast heart rate
• Those with severe symptoms and poor heart function

If you have two or more risk factors for sudden death, your doctor may prescribe preventive treatments such as antiarrhythmic medications or an implantable cardioverter defibrillator (ICD). Most people with HCM have a low risk for sudden cardiac death. Talk to your doctor about any personal concerns.

Medications

Often, medications are used to treat symptoms and prevent further complications. Medications help relax the heart and reduce the degree of obstruction so the heart can pump more efficiently.

Beta-blockers and calcium channel blockers are two classes of medications that may be prescribed. If you have an arrhythmia, your doctor may prescribe medications to control your heart rate or decrease the occurrence of arrhythmias. Your doctor will discuss which medications are best for you.

It is important to know :

• the names of your medications
• what they are for
• how often and at what times to take them
• You may be told to avoid certain medications, such as nitrates because they lower blood pressure, or digoxin, because it increases the force of the heart’s contraction.

Antibiotic medications are prescribed to prevent bacterial endocarditis, a potentially life-threatening condition.

Procedures: septal myectomy, ethanol ablation, pacemaker, ICD

• Septal myectomy
  o During this surgical procedure, the surgeon removes a small amount of the thickened septal wall to widen the outflow tract (the path the blood takes) from the left ventricle to the aorta.
  o Myectomy is considered when medications are not effective in treating HCM.
  o  This frequently eliminates the mitral valve regurgitation.
  o This procedure has a high percentage of positive results
• Ethanol ablation
  o This procedure, also called septal ablation, is performed in the cardiac catheterization laboratory.
  o First, the small coronary artery that supplies blood flow to the septum is located during a cardiac catheterization procedure.
  o A balloon catheter is inserted into the artery and inflated.
  o A contrast agent is injected to locate the thickened septal wall that narrows the passageway from the left ventricle to the aorta.
  o When the bulge is located, a tiny amount of pure alcohol is injected through the catheter.
  o The alcohol kills the cells on contact, causing the septum to shrink back to a more normal size over the following months, widening the passage for blood flow.
• Implantable Cardioverter Defibrillators (ICD)

o ICDs are suggested for patients at risk for life-threatening arrhythmias or sudden cardiac death.
o The ICD is a small device placed just under the skin and is connected to wire leads that are threaded through the vein to the heart.
o An ICD constantly monitors the heart rhythm.
o  When it detects a very fast, abnormal heart rhythm, it delivers energy to the heart muscle to cause the heart to beat in a normal rhythm again.

For patients with non-obstructive HCM

Non-obstructive HCM symptoms may be treated with medications. If heart failure occurs, treatment is aimed at controlling it. (Click here to learn more about heart failure)

Lifestyle changes: 

•  Diet: Drinking at least six to eight, 8-ounce glasses of water a day is important, unless fluids are restricted. In hot weather, you should increase your fluid intake.

Fluid and sodium restrictions may be necessary for some patients if heart failure symptoms are present. Ask your physicians about specific fluid and dietary guidelines, including information about alcoholic beverages and caffeinated products.

• Exercise: Your doctor will tell you if you may exercise or not. Most patients with HCM are able to do noncompetitive aerobic exercise. Heavy weight lifting is not recommended.
• Regular follow-up Visits: Patients with HCM should have an annual follow-up visit with their cardiologist to monitor their condition. Follow-up appointments may be more frequent when HCM is first diagnosed.
• Prevention of Infection:People with HCM may have an increased risk for developing infective endocarditis (click here to learn more about infective endocarditis) Those at risk should follow these precautions:

Tell all your doctors and dentist you have HCM. They should prescribe antibiotics to prevent an infection before performing any procedure that may cause bleeding (dental, respiratory, and gastrointestinal (GI) procedures). Ask your doctor about antibiotic guidelines.

Call your doctor if you have symptoms of an infection, such as temperature of more than 101 degrees Fahrenheit or 38.4 degrees Celsius.

Take good care of your teeth and gums.

Ask your doctor if you need to take endocarditis preventions. For specific guidelines, see Infective Endocarditis .

For information and support

The Hypertrophic Cardiomyopathy Association (HCMA): It may be helpful to talk to others with HCM. The Hypertrophic Cardiomyopathy Association (HCMA) is dedicated to support and educate those with HCM, their families and other health care professionals. They may be contacted at P.O. Box 306, Hibernia, NJ 07842; phone 973/983-7429; email at support@hcma-heart.com or the website at http://www.4hcm.org.