The heart needs strong muscle, but thicker is not always better. Hypertrophic cardiomyopathy (HCM) is a condition in which the heart muscle becomes abnormally thick without another adequate explanation. Some people develop breathlessness, chest pain, palpitations, or fainting; others have no symptoms for years.
One important feature of HCM is that it can run in families. A diagnosis may therefore matter not only to the patient but also to parents, siblings, and children. HCM genetic testing is not a crystal ball. Used correctly, it can help identify which relatives need closer follow-up.
For an overview of cardiovascular genetics, visit our page on genetic testing and counseling in cardiovascular disease.
What is HCM, and why does the heart muscle thicken?
In HCM, thickening most often affects the left ventricle and the septum between the two ventricles. The stiff muscle may make it harder for the heart to relax and fill. In some patients it also narrows the path through which blood leaves the heart.
Not every thick heart wall means HCM. Long-standing high blood pressure, aortic valve stenosis, and intensive athletic training can also cause thickening. Diagnosis therefore combines the examination, electrocardiogram (ECG), echocardiography, sometimes cardiac MRI, and family history.
Is hypertrophic cardiomyopathy inherited?
HCM is often linked to changes in genes that encode proteins involved in heart-muscle contraction. Many inherited forms follow an autosomal dominant pattern. If a person carries a disease-causing variant, each child has a 50% chance of inheriting that variant. Inheritance does not mean that the condition will appear at the same age or with the same severity.
Even within one family, one person may be mildly affected while another has more obvious disease. A genetic result cannot replace clinical assessment.
Who should have HCM genetic testing?
The 2024 AHA/ACC HCM guideline recommends offering genetic testing to people with confirmed or suspected HCM to clarify the genetic basis and help identify relatives at risk. Testing is most informative when it begins with a family member who clearly has the disease—the proband.
A three-generation family history should be recorded before testing. Sudden death at a young age, cardiomyopathy, unexplained heart failure, fainting, or an implanted pacemaker/defibrillator may be relevant clues.
What if the result is positive, negative, or a VUS?
If a pathogenic or likely pathogenic variant is identified, first-degree relatives may be offered targeted testing for that specific variant. This is called cascade testing. Relatives who carry it enter age-appropriate clinical surveillance; those who do not can often avoid repeated screening.
A negative result does not rule out HCM. Current tests cannot detect every genetic cause. If the family history remains convincing, ECG and echocardiographic screening may still be needed.
A variant of uncertain significance (VUS) is not a positive result. It should not, by itself, diagnose HCM, trigger surgery or an ICD, or be used as a predictive test in healthy relatives. Read more in how to interpret a cardiovascular genetic test result.
Does a genetic result determine treatment or surgery?
Usually not. HCM treatment depends on symptoms, rhythm findings, anatomy, outflow obstruction, and established sudden-death risk markers. In adults, genotype alone does not determine whether someone needs an implantable cardioverter-defibrillator or surgical myectomy.
Myectomy may be considered at an experienced center for selected patients with severe obstruction and limiting symptoms despite medication. The major value of genetics is often answering a different question: “Which relatives need screening, and when?”
When should relatives be screened?
First-degree relatives of a person with HCM should receive baseline assessment with an ECG and echocardiogram. The age at which screening begins and how often it is repeated depend on the family’s age of onset, symptoms, sudden-death history, and genetic findings. Children may also need evaluation according to the family context.
Fainting during exercise, unexplained chest pain, sustained palpitations, or sudden death at a young age in the family deserves timely assessment.
What should you bring to an HCM genetics appointment?
- Echocardiography, cardiac MRI, ECG, and rhythm-monitor reports
- Known heart diagnoses and ages at diagnosis in relatives
- Details and, if available, an autopsy report after a sudden death
- The complete report from any previous genetic test
Takeaway
HCM genetic testing is not a universal answer to every thickened heart muscle. When it starts with the right person, it can support diagnosis, focus family screening, and reduce unnecessary surveillance. The result must still be read alongside imaging, ECG findings, and family history.
To discuss HCM or a family history of cardiomyopathy, you can request an appointment through our contact page.
Frequently asked questions
If I have HCM, will my children definitely have it?
No. With an autosomal dominant disease-causing variant, each child has a 50% chance of inheriting it, and not every carrier develops the same degree of disease.
If my genetic test is negative, does my family avoid screening?
Not necessarily. First-degree relatives may still need clinical screening when HCM is present in the family.
Does an HCM gene result decide whether I need surgery?
No. Surgery is based on symptoms, obstruction, imaging, and response to medical treatment—not genotype alone.
Scientific sources: 2024 AHA/ACC HCM Guideline; 2023 ESC Cardiomyopathy Guideline; MedlinePlus patient guide to familial HCM.
This article is for general education and does not replace diagnosis or personal medical advice. Genetic testing and interpretation should be integrated with clinical assessment and, when appropriate, medical genetics expertise.
