(Cardiomyopathy, Hypertrophic—Child; HCM—Child; Idiopathic Hypertrophic Subaortic Stenosis—Child; Asymmetric Septal Hypertrophy—Child; ASH—Child; HOCM—Child; Hypertrophic Obstructive Cardiomyopathy—Child)
Pronounced: hi-per-TRO-fik car-DEE-o-my-AH-pah-thee
Hypertrophic cardiomyopathy (HCM) is a form of cardiomyopathy. This is a condition in which the heart muscle thickens due to genetic problems with the muscle’s structure. As the muscle thickens, it must work harder to pump blood. This strains the heart muscle. Sometimes, the thickened muscle gets in the way of the blood leaving the heart and causes a blockage. This blockage can cause a nearby valve to become leaky. HCM can cause uneven muscle growth. This can cause the heart to pump in a disorganized way. Rarely, it can cause abnormal heart rhythms that can be fatal.
HCM may be caused by a gene that causes an abnormality in the heart muscle. It can be inherited or it can happen from changes in the genes over time.
Symptoms may include:
These symptoms can be caused by some of the side effects of the condition, including abnormal heart beats. The blocked or reduced blood flow is usually the cause of symptoms like lightheadedness, fainting, and difficulty breathing. Babies with the condition may have the following symptoms:
Some children may not have any symptoms. The condition may be suspected if there is a murmur, although not every person with HCM has a murmur and not all murmurs are due to HCM.
You will be asked about your child’s symptoms and medical history. A physical exam will be done.
Images may be taken of your child's bodily structures. This can be done with:
Your child's heart activity will be evaluated. This can be done with:
Your child's bodily fluids will be tested. This can be done with blood tests.
Treatment focuses on controlling symptoms and preventing complications. Talk with the doctor about the best treatment plan for your child. Treatment options include:
Medications may be used to help maintain proper and regular heart function. They may also be used to remove excess fluid from the body. If your child has an arrhythmia, anti-arrhythmic drugs may be given. Your child may also need blood-thinning medication.
The thickened portion of the heart muscle is cut and removed. This may be needed if your child has severely blocked blood flow from the heart or if the blockage causes a problem with the other heart valves and structures. If the mitral valve is leaking, surgery may also be done to repair or replace the mitral valve if needed.
Implantable Cardioverter Defibrillators (ICD)
This ICD is implanted if your child is at increased risk for sudden death.
If a family member has been diagnosed with HCM, your child should be screened for the condition.
American Heart Association
Canadian Cardiovascular Society
Heart and Stroke Foundation of Canada
Cardiomyopathy in children. Cincinnati Children’s Hospital website. Available at:
Erwin JP, Nishimura RA, et al. Dual chamber pacing for patients with hypertrophic obstructive cardiomyopathy: a clinical perspective in 2000. Mayo Clin Proc. 2000;75:173-180.
The HCM Program. St. Luke's Roosevelt Hospital Center website. Available at:
Hypertrophic cardiomyopathy. The Cleveland Clinic website. Available at:
Hypertrophic cardiomyopathy. EBSCO DynaMed website. Available at:
Maron BJ, Nishimura RA, McKenna WJ, et al. Assessment of permanent dual chamber pacing for patients with hypertrophic cardiomyopathy. Circulation. 1999;99:2927-2933.
McCully RB, Nishimura RA, Tajik AJ, Schaff HV, Danielson GK. Extent of clinical improvement after surgical treatment of hypertrophic obstructive cardiomyopathy. Circulation. 1996;94:467-471.
Pediatric cardiomyopathies. The American Heart Association website. Available at:
Last reviewed December 2013 by Kari Kassir, MD