Hypertrophic cardiomyopathy is characterized by the abnormal growth of muscle fibers on the heart muscle, often causing a thickened septum. The thickening of the muscle can result in a resistance of blood flow both in and out of the heart’s chambers. When this occurs, the heart must work harder to pump blood throughout the body.

Hypertrophic cardiomyopathy is generally considered a genetic disease that affects about one percent of the population, or one in 500 people. Most hypertrophic cardiomyopathy shows no symptoms. However, if symptoms develop, they most often occur during puberty and young adulthood. A possibly related condition, called inappropriate left ventricle hypertrophy, occurs in people over 60.

Among patients who develop symptoms, most are mild to moderate and progress slowly with age. Among a small subset of patients, however, symptoms can be severe and life threatening. These patients are at increased risk for sudden cardiac death, stroke and heart failure. According to the American Heart Association, 36 percent of young athletes who die suddenly have definite or probable hypertrophic cardiomyopathy.

The name hypertrophic cardiomyopathy is derived from the following:

Whether or not patients are experiencing symptoms, it is important to avoid strenuous exercises such as weight lifting. Unless otherwise advised by a physician, controlled aerobic exercises such as walking or even running, can be safe. However, these forms of exercise should never continue to the point of dehydration and/or exhaustion because this could trigger a potentially fatal abnormal heart rhythm (arrhythmia). Other strategies to maintain a normal heart rhythm include taking antiarrhythmic medications and the surgical insertion of a pacemaker or implantable cardioverter defibrillator.

In about 5 percent of patients, surgery to reduce the size of the septum (septal myomectomy) may be necessary. Alternatively, a procedure called septal alcohol ablation may be used. During this catheter-based procedure, a physician injects alcohol into the blood supply to the septal part of the left ventricle heart muscle, causing the outflow track of the left ventricular pumping chamber to allow more blood flow to the body.

While hypertrophic cardiomyopathy is a potentially serious condition, sometimes with an unpredictable onset of symptoms, many patients experience only minor intrusion from the disease, enjoying a normal lifespan without the need for major medical procedures.

Hypertrophic cardiomyopathy is characterized by an abnormal growth of muscle fibers on the heart muscle. This abnormal growth may result in the thickening and stiffening of the septum – a muscular structure separating the right and left ventricles. Because of the rigidity of the muscle, the ventricle cannot relax properly and the mitral valve may be compromised. The ejection fraction may be higher than normal (60 to 90 percent). Although most patients with hypertrophic cardiomyopathy never experience symptoms, the condition may result in heart failure, sudden cardiac death, stroke, arrhythmias and other cardiac events.

Hypertrophic cardiomyopathy is generally considered a genetic disease. It is an autosomal dominant condition. “Autosomal” means that it can occur in either males or females. “Dominant” basically means that there is a 50 percent chance that a child will inherit a condition (at conception) if one parent has the condition, or a 75 percent chance if both parents have the condition.

Although it runs in families, the nature of the disease may vary widely among family members having the condition. For example, a parent may have only minor hypertrophy and few – if any – symptoms, while a sibling or older child may have pronounced thickening and more obvious symptoms. Symptoms are rare in young children and, if they are going to develop, they tend to appear in the teen years.

Currently, about 150 different genetic mutations have been identified for hypertrophic cardiomyopathy. A mutation is an alteration of a region of DNA on a gene. The mutations in hypertrophic cardiomyopathy affect proteins involved in normal contraction of heart muscle. Genetic mutations can be either inherited or occur spontaneously during fetal development.

While genetic factors are known to play a role in the development of hypertrophic cardiomyopathy, researchers are still working to identify the complex interaction between genes that results in the condition. For example, researchers have linked hypertrophic cardiomyopathy with irregularities in the connective tissue of the heart, which are arranged in a disorganized and abnormal pattern. Ultimately, genetic testing might enable physicians to better understand why the disease is so variable, even among family members, and better design treatments.

There are several types of hypertrophic cardiomyopathies, including:

If the thickening is more localized to the septum of the ventricle than the rest of the left ventricle, the condition is also known as asymmetrical septal hypertrophy (ASH). If there is an evenly distributed thickening of the entire ventricle, including the septum and wall, then the condition is also known as concentric hypertrophy. In cases where the hypertrophy is localized to the apex of the left ventricle, the condition is known as apical cardiomyopathy.

In very advanced cases, the condition may closer resemble dilated cardiomyopathy, with an expanded and thinned left ventricle. This is sometimes known as "end stage" or "burned out" hypertrophic cardiomyopathy and is related to a higher death rate.

Most individuals with hypertrophic cardiomyopathy have no symptoms. They are born with it and live with it for decades – even into their 70s and 80s – without it affecting their lifestyle in any way. The diagnosis might be made accidentally during routine tests.

Other patients are diagnosed with a hypertrophic cardiomyopathy after they have begun to experience symptoms, such as:

In a minority of severe cases, patients may also experience symptoms of heart failure, which may include one or more of the following:

In very rare instances, hypertrophic cardiomyopathy can lead to sudden cardiac death, which sometimes can be the first and only sign of the disease. In fact, non-obstructive hypertrophic cardiomyopathy is believed to be a major cause of death in young athletes. According to the American Heart Association, 36 percent of young athletes who die from sudden cardiac death have hypertrophic cardiomyopathy.

Depending on the severity of the disease, women with hypertrophic cardiomyopathy may have an increase of symptoms (e.g., fatigue, shortness of breath) during pregnancy. The risk of mortality is very low, and typically applies to those with severe disease. For most women, though, hypertrophic cardiomyopathy should not interfere with a successful pregnancy and delivery.

The first step to diagnosing hypertrophic cardiomyopathy is usually obtaining the patient’s family history. Studies have shown that first-degree family members of someone with hypertrophic cardiomyopathy are at greater risk of developing the condition. For this reason, family screening is usually recommended among families with hypertrophic cardiomyopathy.

To diagnose cardiomyopathy, physicians will conduct on a complete physical examination with specific focus on the heart and lungs. Physicians may detect abnormal heart sounds or a murmur through a stethoscope. In most cases, there will be no definitive indication of the condition through a physical exam.

If cardiomyopathy is suspected, the physician can order any number of tests to help with the diagnosis, including:

• Echocardiogram with Doppler ultrasound. This is a non-invasive test that utilizes sound waves to measure the structure and function of the heart. It is the most common test used to diagnose hypertrophic cardiomyopathy. The test produces images that allow a physician to measure the muscle thickness, velocity and blood flow in the heart. It can also determine the ejection fraction, which tends to be abnormal with cardiomyopathies.
  
  During diagnosis, the physician will attempt to measure the degree of outflow obstruction, or the degree to which blood is prevented from flowing normally out of the left ventricle. Patients with greater outflow obstruction are more likely to suffer long-term complications from their condition, although there is not a strong connection between outflow obstruction and the severity of symptoms.
  
  
  

  

• Stress testing. This test is valuable to measure the patient's tolerance for physical activity, as well as detecting any possible arrhythmias. During this test, the patient is asked to exercise while their heart's electrical activity is carefully monitored with an electrocardiogram machine. If a patient cannot exercise, drugs will be administered to mimic exercise. Patients may also be asked to wear a Holter monitor, which records the heart's activity over a period of time - usually 24 to 72 hours.
  
  
• Studies have found that the combination of reduced velocity during diastole (the heart's relaxation phase) and high ejection fraction occur in hypertrophic cardiomyopathy.
  
  
• Chest x-ray. This radiation imaging test allows physicians to view the size and position of the heart.
  
  
• Cardiac catheterization. In this procedure, a thin catheter is placed into an artery, usually in the groin area, which is fed up into the chambers of the heart. The catheter can be used to take pressure measurements in the heart or to deliver contrast medium (dye). The dye can outline the heart and vessels and can detect blockages in the arteries.

Diagnosing the condition in physically active individuals – especially trained athletes – can be challenging. Heart enlargement can be pathological (related to significant heart disease) or physiological (related to exercise or other physical activity). Sometimes referred to as “athlete's heart,” physiological heart enlargement can occur in high-level athletes who engage in regular, sustained and often intense exercise. In most cases, this is not a medically significant or dangerous condition. Studies are exploring ways to better distinguish an enlarge heart from hypertrophic cardiomyopathy. Some researchers feel that a thickness of the left ventricular wall greater than 12 millimeters for male teenage athletes (11 millimeters for female teenage athletes) may be an indication of the disease.

At this point, clinical diagnosis continues to be made on the basis of degrees of hypertrophy. The main obstacle is that individuals with hypertrophic cardiomyopathy can have varying degrees of hypertrophy and symptoms.  In addition, the condition can  develop at different ages, even among members of the same family. With the ongoing progress in identifying the genes and mutations associated with hypertrophic cardiomyopathy, it is hoped that genetic testing will eventually offer an accurate, early way of screening and diagnosing the condition.

Whether hypertrophic cardiomyopathy  is diagnosed in individuals without symptoms or diagnosed during a family screening, a number of measures may be recommended. Typically, this means limiting physical activity and exercise to aerobic exercises and non-competitive sports that are not pursued to the point of either exhaustion of dehydration. Weightlifting and other isometric exercises should generally be avoided.

Hypertrophic cardiomyopathy often occurs in children, teens or young adults. This group tends to be more active by nature. The American Heart Association recommends that children and young adults should be evaluated by their physicians specifically to determine which recreational sports are safe and which physical activities should be avoided.

If people are not experiencing any symptoms, then a cardiologist might recommend only these activity restrictions and regular follow-up visits. An echocardiogram would typically be done at each of these visits. A search for electrical disturbances of the heart is imperative, even in an individual who does not exhibit symptoms.

If symptoms are present, or symptoms and signs of a problem are evident in testing, such as Holter monitoring, exercise stress testing, and other tests, the first course of treatment is often medications. These medications may be prescribed to relieve symptoms, such as shortness of breath, electrical disturbances of the heart, as well as to prevent heart failure. These medications include:

If medication is not successful, a permanent pacemaker may be considered. A pacemaker controls the heartbeat by pacing the heart at a slightly faster rate than the patient’s natural heartbeat. This treatment may be successful in reducing the major symptoms, chest pain and shortness of breath, in about 50 percent of patients. It is typically used in patients with hypertrophic obstructive cardiomyopathy (HOCM). By creating an abnormal pattern of electrical activity in the ventricle, the extent of the obstruction by the thickened muscle can be reduced. Pacemakers may not be as effective in reducing symptoms of hypertrophic cardiomyopathy as other forms of treatment.

In about five percent of cases, the blockage created by the heart’s enlargement must be reduced by surgical means. One procedure used is a septal myomectomy. During this surgery, the physician gains access to the left ventricle through the aortic valve. Once inside the heart, the physician removes part of the thickened septum (the muscular wall between the left and right ventricles). Recent research has shown that myomectomies are very effective at extending the life of patients who undergo the procedure. More than 75 percent of patients show some long-term improvement after this procedure.

In some cases, the mitral valve may need to be repaired or replaced at the same time. A mitral valve replacement may allow for the reduction of a severe leakage, called mitral regurgitation, which can contribute to symptoms of heart failure in this situation.

A relatively new procedure called septal alcohol ablation is also available for people with hypertrophic obstructive cardiomyopathy. This catheter-based procedure involves the destruction of certain heart cells with ethanol (alcohol) to shrink the heart muscle and increase the space for blood to flow. The ethanol can be placed in a specific branch of one of the heart’s arteries that provides blood to the septum. Results have been promising, showing long-term benefit as well as shorter recovery periods compared to traditional surgery. One common complication, however, has been the development of heart block, requiring implantation of a pacemaker. But researchers are already seeing a decrease in the rate of complications as the technique has evolved. This procedure may be recommended for patients who cannot withstand the rigors of surgery, but not all patients are candidates for this treatment. Research continues to evaluate the long-term effectiveness and safety of septal alcohol ablation.

Because a hypertrophic cardiomyopathy can cause potentially fatal arrhythmias, an electrophysiology study may be performed to determine whether an internally implantable cardioverter defibrillator (ICD) is necessary. In an electrophysiology study, the physician feeds a thin tube (catheter) through a blood vessel (usually a vein to the right ventricle. There, the physician tries to create a very fast heart rhythm (ventricular tachycardia) by introducing premature electrical impulses. If no ventricular tachycardia is created, then the patient is judged to be at lower risk of experiencing this condition in the future. On the other hand, if the ventricular tachycardia was elicited, an ICD may be necessary. Those with a family history of sudden cardiac death should be considered particularly at risk for an ICD.

An ICD may benefit patients who have experienced serious episodes of fainting (syncope), have been resuscitated from cardiac arrest or have experienced certain brief arrhythmias that occur without symptoms (a condition known as nonsustained ventricular tachycardia).

Because this disease appears to have a genetic component, there is no known way to prevent it. However, if there is family history of sudden cardiac death – even from no known cause – it is recommended that close relatives (e.g., siblings, children) see a cardiologist for a physical examination and echocardiogram to rule out or confirm early signs of disease.

Preparing questions in advance can help patients and their families have more meaningful discussions with their physicians regarding their conditions. Patients or parents may wish to ask their doctor the following questions about hypertrophic cardiomyopathy:

1. How can you tell that I have hypertrophic cardiomyopathy?
   
   
2. What tests will be used to diagnose this condition?
   
   
3. What are my treatment options?
   
   
4. What are the risks associated with these treatments?
   
   
5. If medication is recommended, what type will I be prescribed?
   
   
6. Will different medications be tried if some are unsuccessful?
   
   
7. Could any medications I am currently taking interfere with or complicate my condition in any way?
   
   
8. Is there a chance I will need surgery to correct the condition?
   
   
9. Will my condition get worse as I age?
   
   
10. What is my prognosis with and without treatment?
    
    
11. What are my exercise and sports restrictions with this condition?
    
    
12. What are the chances that I will have a child with this condition?
    
    
13. Should I or other family members undergo genetic testing?
    
    
14. Can you refer me to a genetic counselor?