Hypertrophic Cardiomyopathy in Children

What is hypertrophic cardiomyopathy?

Hypertrophic cardiomyopathy (HCM) is a condition that affects the heart muscle causing it to become thickened and “muscle-bound”. In HCM, the muscle cells are enlarged (the medical term for this is hypertrophy). This causes the heart walls to be thick. This effect is seen most in the ventricular septum, which is the wall between the heart’s two lower chambers (the ventricles). The ventricles are the primary pumping chambers of the heart with the right ventricle pumping blood to the lungs and the left ventricle pumping blood to the body. 

In some cases, the wall between the two ventricles becomes so thick that it blocks blood flow out of the heart.  

Hypertrophic cardiomyopathy symptoms

While many children with HCM have no symptoms, some may experience symptoms with exercise which may include lightheadedness, difficulty breathing or chest pain. HCM has been linked to life-threatening abnormal heart rhythms that result in syncope (passing out or loss of consciousness) or sudden death. It is a common cause of sudden death in young athletes.

How common is hypertrophic cardiomyopathy

HCM can be inherited meaning it can be passed from one generation to the next. A diagnosis of one person in the family should lead to a family screening to determine who else might be affected. It is quite common for a genetic disease, affecting about 1 in 500 adults. Many are not diagnosed until adulthood making it far less common in childhood, though it affects an estimated 1 in 200,000 children.

How hypertrophic cardiomyopathy affects children’s health

Although HCM is a serious problem, the health effects vary widely with the age it starts and how severe it is. 

  • Most children with HCM will not show any symptoms and will be at low risk for sudden death. 
  • Treatments, such as medication or surgery, can help improve symptoms for children with symptoms such as chest pain or low endurance with exercise, helping them maintain an active lifestyle. 
  • For children who are determined to be at high risk of sudden death, a device called an ICD (see below) can be placed to help significantly lower that risk. 

HCM is a progressive condition (meaning it can get more severe with time) and your child will need to be monitored regularly as they get older.

Hypertrophic cardiomyopathy diagnosis

There are a few factors that trigger an initial HCM evaluation. These include: 

  • Family history: HCM is quite commonly an inherited condition and many children with HCM are identified during family screenings after another family member has been identified with the condition. Even children who have no previous family history of HCM can pass it on to their children (as the condition may be due to a new genetic mutation that can now be passed on).
  • Symptoms: Possible symptoms include palpitations ("heart-racing" or "skipping heartbeat"), chest pain and shortness of breath with physical activity, and fainting (syncope).
  • Physical findings: The exam is usually normal other than a heart murmur.

If one or more of the above factors are identified, further medical testing can confirm the HCM diagnosis. These medical tests include:

Electrocardiogram (EKG or ECG)

An EKG records the electrical signal from your heart. It is often the first test performed in any child who may have a cardiac condition. An EKG is often abnormal in people with significant HCM, but it is not a very sensitive test and may show a normal result for others, especially early in the course of the disease.

Echocardiogram (ECHO)

An ECHO uses sound waves to create pictures of your heart. It is the main test used to make the diagnosis of hypertrophic cardiomyopathy. It can detect thickening of the heart muscle which is the characteristic feature of hypertrophic cardiomyopathy.

Magnetic Resonance Imaging (MRI)

An MRI uses a strong magnet to create pictures. It is like an ECHO in that it assesses the structure and function of the heart. It can be more sensitive than an ECHO in that it can detect hypertrophy in parts of the heart that are not well seen on an ECHO. It can detect areas of scarring in the heart which may be associated with higher risk of dangerous arrhythmias and sudden death.

Holter monitor

A Holter monitor records the rhythm of the heart for a duration of 1 day to 2 weeks. It will help detect any arrhythmias that may require special treatment through medication or placing an implantable cardioverter-defibrillator (ICD).

Hypertrophic cardiomyopathy treatment

There are several ways HCM can be treated, including:

Medications 

The primary medication used to treat HCM is a beta-blocker. Beta-blockers tend to slow the heart rate which can allow more time for the heart to fill with blood between beats. This can be helpful for people with HCM who have heart stiffness that weakens the heart’s ability to fill easily (diastolic dysfunction). 

A heart with more blood and a slower heart rate can also be helpful in people with excess heart muscle that blocks (obstructs) the ability of blood to get out of the heart during a contraction (obstructive HCM). 

Other medicines that can be used to help alleviate symptoms include calcium channel blockers (such as verapamil) and disopyramide. There are newer medicines (such as myosin inhibitors) being evaluated in research studies, but none have yet been approved for use by the FDA. Medications are usually recommended for people that have symptoms but may be considered for people without symptoms who have HCM with significant blockage.

Surgery

In some people with HCM, the excess muscle in the left ventricle can get in the way of blood getting out of the heart. This can be especially noticeable with exercise and can lead to lightheadedness or fainting with exercise or standing up too quickly. The medications mentioned above may help improve symptoms significantly, but children with muscular blockage who still have symptoms with medication may benefit from a surgical myectomy, a procedure to remove the muscle that is blocking blood from getting out of the heart. 

Implantable Cardioverter-Defibrillator (ICD)

Patients with HCM can be at risk of sudden death. An ICD may be recommended for people with HCM who have had a cardiac arrest or who are at risk for one based on their evaluation. The ICD continuously monitors the heartbeat and if it detects a dangerous heart rhythm it will reset the heart using a small electric shock. 

Exercise restrictions/safe environment

We very much encourage children with HCM to remain active. There are many benefits to physical activity and even team sports are possible if conditions can be met to maximize the safety of the child. Every child and situation are different, so your health care team will work with your child, your family and others (including coaches, school staff, school nurses and trainers) to identify activities and environments with a good chance of safety. School staff, teachers, gym instructors and coaches should be aware of the child’s medical condition and have a plan ready so they can respond in case of an emergency.

Long-term outlook

While HCM can be a serious problem, most children have no symptoms and are at low risk of a dangerous heart arrhythmia leading to sudden death. They should be monitored regularly depending on their age, symptoms and degree of heart thickening. 

HCM is a progressive condition, meaning that it will get worse as a person gets older. However, the rate, timing and degree of progression can vary from one person to the next. Perhaps the greatest rate of change occurs when children become teens (adolescence). They should be followed more closely during this time so that their exercise guidelines and risk assessments can be updated appropriately.

Exercise guidelines

Personal exercise recommendations are developed in discussions involving your child, your family and your doctor. As noted above, exercise is important, and encouraged, after discussions about safe activities. In general, children with HCM should be allowed to self-limit their exercise and they should not be graded on their performance (which could pressure them to push past their limit of comfort). 

Why choose C.S. Mott Children’s Hospital

The Congenital Heart Center at University of Michigan Health C.S. Mott Children’s Hospital has developed a team-based approach to care for patients and families affected by HCM and other inherited cardiomyopathies. The team includes cardiologists who specialize in cardiomyopathy, heart failure and rhythm disorders among other subspecialties. The team also includes a nurse practitioner, genetic counselor, social worker and child life specialist. Counselors familiar with the challenges of an HCM diagnosis are also available for support.

Mott is a Children’s Cardiomyopathy Foundation (CCF) accredited center of care. CCF recognizes centers that manage a high volume of pediatric cardiomyopathy patients, offer a variety of pediatric patient services, specialize in the treatment and management of cardiomyopathy in children, and are affiliated with an academic research institution. 

We participate in a variety of research projects aimed toward improving the health outcomes and quality of life for children and families with cardiomyopathy.

Transition to adult care

HCM is a progressive condition that is more common in adults. For this reason, we work very closely with our colleagues in adult cardiology at the Frankel Cardiovascular Center’s Inherited Cardiomyopathy Program to create consistency for patients and families as patients transition from childhood to adulthood. We meet monthly to discuss patient care issues, to update research activities and to identify opportunities to enhance or improve care practices. In addition, both the adult and pediatric teams are assisted by the same genetic counselor who provides care for the whole family, coordinates family screenings and facilitates follow-up.

Appointment & Information

To make an appointment with our team, or to learn more about the Congenital Heart Center, please call 734-764-5176.