The aim of this information sheet is to explain what hypertrophic cardiomyopathy is, what effect it will have on a child and how it can be treated.
Hypertrophic means thickening. Cardio means of the heart. Myopathy is any disease of muscles. Hypertrophic cardiomyopathy (HCM) means a thickening of the heart muscle.
HCM is usually caused by a mutation (a genetic mistake). The condition can cause the heart muscle walls to thicken. This thickening occurs in the absence of any other factor or structural disorder in the heart. In some areas of the heart, the muscle cells may be found to be ‘disorganised’ (not arranged in the normal way).
SVC: Superior vena cava PV: Pulmonary valve IVC: Inferior vena cava PA: Pulmonary artery
When the heart beats, it contracts to pump blood out to the body and lungs, and relaxes to fill with blood again. The function of the heart is affected by HCM.
The left ventricle (pumping chamber) does not pump enough blood. There are two reasons for this.
Firstly, the thickened muscle around it makes the ventricle smaller. This means that it does not hold as much blood as in a normal heart.
Secondly, the thickened muscle cannot relax very much so less blood is able to enter the ventricle.
HCM affects approximately 1 in 500 of the population.
Most cases of hypertrophic cardiomyopathy are caused by mutations (mistakes) in the genes. Children are not usually affected by symptoms until they are teenagers, but some do have symptoms when they are still young. It has been estimated that children only account for about 10% of HCM cases. Most cases are hereditary so screening seems to be recommended for only close, first degree relatives.
Not everyone with HCM will have any symptoms. Symptoms may develop at any stage in life and do not reflect the severity of the condition.
Possible symptoms include:
HCM may be suspected in your child because a relative has been diagnosed with the condition. HCM may occur together with other genetic conditions such as Noonan syndrome or mitochondrial disorders. Sometimes HCM is a congenital problem, meaning that it emerges during the development of the foetus, but the cause may not be clear. Once the condition has been diagnosed, doctors will investigate further to identify if there is an underlying cause.
HCM is a very variable condition. Some people have mild symptoms, others have severe symptoms. Sometimes the symptoms are progressive, but often once the thickening stops, it remains quite stable. Regardless of symptoms, they will need regular monitoring. This will include ECGs, echocardiograms and 24 hour monitoring. The frequency and tests needed depend upon the symptoms your child has and the findings of previous tests.
Contact the cardiologist if your child experiences any of the following symptoms:
HCM can be improved and controlled by treatment including:
Evidence and sources of information for this CHF information sheet can be obtained at:
(1) National Institute for Health and Care Excellence. Implantable cardioverter defibrillators and cardiac resynchronisation therapy for arrhythmias and heart failure. Guidance TA314. London: NICE; 2017. Available at:
(2) Cardiomyopathy UK. Cardiomyopathy UK booklet: ‘Living with cardiomyopathy’. London: Cardiomyopathy UK; 2017. Available at:
(3) British Heart Foundation. Hypertrophic cardiomyopathy. London: BHF; 2017. Available at:
About this document:
Published: June 2015
Reviewed: June 2017
Due for review: June 2019
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