Table of ContentsView AllTable of ContentsGeneticsMutationsRisk FactorsNext in Hypertrophic Cardiomyopathy GuideHow Hypertrophic Cardiomyopathy Is Diagnosed
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Table of Contents
Genetics
Mutations
Risk Factors
Next in Hypertrophic Cardiomyopathy Guide
This article discusses HCM and its causes, including genetics and risk factors for complications.
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Genetics of Hypertrophic Cardiomyopathy
While mutations that cause HCM are usually passed down from a family member, usually in an autosomal dominant way, they can also be sporadic in some cases, meaning the mutation occurs randomly, without a parent being affected.
Adding to the complexity, however, is the fact that several different types of mutations exist. And even people who have inherited a mutation that causes HCM may not develop it or its complications, a phenomenon known as variable penetrance.
Furthermore, someone with HCM may have more or less severe symptoms than a family member, which is known as variable expression.
Mutations That Cause Hypertrophic Cardiomyopathy
Sarcomere Mutations
The most common type of mutations that cause HCM are mutations insarcomericproteins in the heart.
Sarcomeresare proteins found in muscle cells. Mutations in sarcomeres that cause HCM result in thickening of the heart muscle, disorganized muscle fibers, and scarring.
The following is a list of mutations in sarcomeric proteins known to cause HCM:
In people who have a sarcomere mutation, mutations in beta myosin heavy chain and myosin binding protein C3 are the most common causes. They are found in about 70% of cases. The other sarcomere mutations each account for only 1%–5% of HCM mutations.
Genetic testing is performed in people whose imaging tests reveal signs of HCM. It is particularly useful after adiagnosis of HCMto test family members for the gene mutation.
RecapMany different genetic mutations can cause HCM, and people with a mutation have variable severity—such as not having HCM or developing symptoms later in life. Mutations in sarcomeres, which make up heart muscle fibers, are responsible for most HCM cases.
Recap
Many different genetic mutations can cause HCM, and people with a mutation have variable severity—such as not having HCM or developing symptoms later in life. Mutations in sarcomeres, which make up heart muscle fibers, are responsible for most HCM cases.
Variants of Uncertain Significance
Not everyone with HCM has an identified mutation that has been shown to cause HCM. Some people may have variants in the related genes, but it remains unclear if they are the cause of HCM. These are known as “variants of uncertain significance.”
As our understanding of genetics in HCM evolves, these variants may be further clarified.
Risk Factors for Sudden Cardiac Death
Heart muscle thickening, disorganization, and scarring in HCM can lead to arrhythmias andsudden cardiac death. In fact, HCM is the most commonly identified cause of sudden death in athletes younger than 30 years old.
Healthcare providers use risk factors to determine the risk of sudden death and make recommendations aboutexercise restrictionsandimplantable cardioverter defibrillators(ICDs). These devices monitor the heart rhythm and provide a shock of electricity to stop dangerous arrhythmias.
The following are factors found to be associated with increased risk of SCD.
Sudden Cardiac Death in a Family Member
The risk of sudden death is increased if a family member has experienced SCD. This is particularly true when the family member is a close relative (first or second degree relative) and was less than 50 years of age at the time of death.
Findings on Heart Imaging
The leftventricleis the main muscular chamber of the heart that pumps blood to the body. Noninvasive imaging tests, such asechocardiogramand cardiacmagnetic resonance imaging(MRI), give information about the left ventricle that can predict who is at higher risk of SCD.
Findings that may indicate HCM include:
History of Unexplained Syncope
Those with HCM who have had recent unexplained fainting spells are also at risk of SCD. “Unexplained” syncope, or fainting, means that there was no obvious cause of loss of consciousness, such as avasovagal event(for example, passing out when getting blood drawn).
Findings on Heart Rhythm Monitoring
People with HCM undergo heart rhythm monitoring to evaluate for arrhythmias. Those whose rhythm monitoring show an arrhythmia callednonsustained ventricular tachycardia(NSVT) that are frequent, long, or very fast, are at higher risk of SCD.
Treating HCM
Fortunately, there are many effective and promisingtreatments for HCM. These include:
Summary
A Word From Verywell
Finding out that you have a genetic mutation for hypertrophic cardiomyopathy can provoke anxiety, especially if other family members have experienced problems from thickened heart muscle. Know that not everyone with the mutation goes on to have detectable heart problems, and there are many promising treatments for people with HCM. Cardiac testing will help you and your healthcare provider determine a treatment and follow-up plan.
6 SourcesVerywell Health uses only high-quality sources, including peer-reviewed studies, to support the facts within our articles. Read oureditorial processto learn more about how we fact-check and keep our content accurate, reliable, and trustworthy.National Institutes of Health: Genetic and Rare Diseases Information Center.Familial hypertrophic cardiomyopathy.Maron BJ.Clinical course and management of hypertrophic cardiomyopathy.N Engl J Med. 2018;379(7):655-668. doi:10.1056/NEJMra1710575Marian AJ, Braunwald E.Hypertrophic cardiomyopathy: genetics, pathogenesis, clinical manifestations, diagnosis, and therapy.Circ Res. 2017;121(7):749-770. doi:10.1161/CIRCRESAHA.117.311059Ommen SR, Mital S, Burke MA, et al.2020 AHA/ACC guideline for the diagnosis and treatment of patients with hypertrophic cardiomyopathy: a report of the American College of Cardiology/American Heart Association Joint Committee on Clinical Practice Guidelines.Circulation. 2020;142:e558–e631. doi:10.1161/CIR.0000000000000937Drezner JA, Malhotra A, Prutkin JM, et al.Return to play with hypertrophic cardiomyopathy: are we moving too fast? A critical review.Br J Sports Med. 2021;55(18):1041-1047. doi:10.1136/bjsports-2020-102921Maron MS, Ommen SR.Exploring new and old therapies for obstructive hypertrophic cardiomyopathy: mavacamten in perspective.Circulation. 2021;143(12):1181-1183. doi:10.1161/CIRCULATIONAHA.120.051330
6 Sources
Verywell Health uses only high-quality sources, including peer-reviewed studies, to support the facts within our articles. Read oureditorial processto learn more about how we fact-check and keep our content accurate, reliable, and trustworthy.National Institutes of Health: Genetic and Rare Diseases Information Center.Familial hypertrophic cardiomyopathy.Maron BJ.Clinical course and management of hypertrophic cardiomyopathy.N Engl J Med. 2018;379(7):655-668. doi:10.1056/NEJMra1710575Marian AJ, Braunwald E.Hypertrophic cardiomyopathy: genetics, pathogenesis, clinical manifestations, diagnosis, and therapy.Circ Res. 2017;121(7):749-770. doi:10.1161/CIRCRESAHA.117.311059Ommen SR, Mital S, Burke MA, et al.2020 AHA/ACC guideline for the diagnosis and treatment of patients with hypertrophic cardiomyopathy: a report of the American College of Cardiology/American Heart Association Joint Committee on Clinical Practice Guidelines.Circulation. 2020;142:e558–e631. doi:10.1161/CIR.0000000000000937Drezner JA, Malhotra A, Prutkin JM, et al.Return to play with hypertrophic cardiomyopathy: are we moving too fast? A critical review.Br J Sports Med. 2021;55(18):1041-1047. doi:10.1136/bjsports-2020-102921Maron MS, Ommen SR.Exploring new and old therapies for obstructive hypertrophic cardiomyopathy: mavacamten in perspective.Circulation. 2021;143(12):1181-1183. doi:10.1161/CIRCULATIONAHA.120.051330
Verywell Health uses only high-quality sources, including peer-reviewed studies, to support the facts within our articles. Read oureditorial processto learn more about how we fact-check and keep our content accurate, reliable, and trustworthy.
National Institutes of Health: Genetic and Rare Diseases Information Center.Familial hypertrophic cardiomyopathy.Maron BJ.Clinical course and management of hypertrophic cardiomyopathy.N Engl J Med. 2018;379(7):655-668. doi:10.1056/NEJMra1710575Marian AJ, Braunwald E.Hypertrophic cardiomyopathy: genetics, pathogenesis, clinical manifestations, diagnosis, and therapy.Circ Res. 2017;121(7):749-770. doi:10.1161/CIRCRESAHA.117.311059Ommen SR, Mital S, Burke MA, et al.2020 AHA/ACC guideline for the diagnosis and treatment of patients with hypertrophic cardiomyopathy: a report of the American College of Cardiology/American Heart Association Joint Committee on Clinical Practice Guidelines.Circulation. 2020;142:e558–e631. doi:10.1161/CIR.0000000000000937Drezner JA, Malhotra A, Prutkin JM, et al.Return to play with hypertrophic cardiomyopathy: are we moving too fast? A critical review.Br J Sports Med. 2021;55(18):1041-1047. doi:10.1136/bjsports-2020-102921Maron MS, Ommen SR.Exploring new and old therapies for obstructive hypertrophic cardiomyopathy: mavacamten in perspective.Circulation. 2021;143(12):1181-1183. doi:10.1161/CIRCULATIONAHA.120.051330
National Institutes of Health: Genetic and Rare Diseases Information Center.Familial hypertrophic cardiomyopathy.
Maron BJ.Clinical course and management of hypertrophic cardiomyopathy.N Engl J Med. 2018;379(7):655-668. doi:10.1056/NEJMra1710575
Marian AJ, Braunwald E.Hypertrophic cardiomyopathy: genetics, pathogenesis, clinical manifestations, diagnosis, and therapy.Circ Res. 2017;121(7):749-770. doi:10.1161/CIRCRESAHA.117.311059
Ommen SR, Mital S, Burke MA, et al.2020 AHA/ACC guideline for the diagnosis and treatment of patients with hypertrophic cardiomyopathy: a report of the American College of Cardiology/American Heart Association Joint Committee on Clinical Practice Guidelines.Circulation. 2020;142:e558–e631. doi:10.1161/CIR.0000000000000937
Drezner JA, Malhotra A, Prutkin JM, et al.Return to play with hypertrophic cardiomyopathy: are we moving too fast? A critical review.Br J Sports Med. 2021;55(18):1041-1047. doi:10.1136/bjsports-2020-102921
Maron MS, Ommen SR.Exploring new and old therapies for obstructive hypertrophic cardiomyopathy: mavacamten in perspective.Circulation. 2021;143(12):1181-1183. doi:10.1161/CIRCULATIONAHA.120.051330
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