Hypertrophic Cardiomyopathy (HCM) and Family Health History of Sudden Death

a heart with Hypertrophic Cardiomyopathy


If you have a family member, especially a parent, sibling, or child, who died suddenly before age 40, let your doctor know. You might need to be screened for HCM, a genetic condition that causes the heart muscle to become thick and can lead to sudden death. While some people with HCM are very sick, many people, especially children, teens, and young adults, have no or few symptoms and may not know they have a heart problem. Sharing your family history with your doctor can help you and other relatives find HCM early, check regularly for changes to the heart, and determine the need for future treatment.

What is Hypertrophic Cardiomyopathy?

Hypertrophic cardiomyopathy is a common genetic disorder that affects about 1 in 5001 people and causes the heart muscle to become thicker and stiff.2,3 This makes it harder for the heart to work properly because:

  • The thickened heart muscle can obstruct blood flow out of the heart.
  • The heart requires more energy and oxygen to work, especially during exercise.
  • The heart can hold less blood, so the amount of blood pumped to the rest of the body with each heartbeat is decreased.

People with HCM can develop complications such as heart failure, atrial fibrillation, ventricular tachycardia, and ventricular fibrillation.2 HCM can lead to sudden death, especially in children, young adults, and competitive athletes,2,4 who may not be aware of their risk or have symptoms of HCM.

HCM can develop at any point in a person’s life. Most people with HCM are born with what appears to be a normal heart and develop HCM later. Those who develop HCM before age 40 often have more symptoms and complications. 5

Family health history, genetics, and cascade testing for HCM

HCM sometimes runs in families. In such cases, a child of an affected parent has a 50% (1 in 2) chance of having HCM. 6 Other family members also have an increased chance of having HCM. Importantly, the age at which other family members develop HCM can vary within families.

When collecting your family health history to assess your risk for HCM:

  • Include information on family members who died suddenly, especially if they were younger than age 40.
  • Include information on family members with heart failure, atrial fibrillation, ventricular tachycardia, ventricular fibrillation, stroke, heart attack, heart transplant, or implantable cardioverter-defibrillator (ICD) (like a pacemaker).
  • Update information regularly, and let your doctor know about any new diagnoses, cardiac events, or sudden deaths in your family.

HCM is caused by changes in genes that control the production of heart muscle proteins. 6 You only need a change in one copy of the gene to develop HCM. If someone in your family has been diagnosed with HCM, that person can have genetic testing to look for genetic changes that cause HCM. Testing in your family should start with someone who has HCM. In cases in which a young person died suddenly, genetic testing might have been done as part of the autopsy.

Once the genetic change that causes HCM is found in a person, other family members can have genetic testing for that change. If genetic testing does not find a genetic change that causes HCM in the affected family member, they should follow up with their cardiologist (heart doctor) on a regular basis. Sometimes genetic testing finds a genetic change that is not known to cause HCM at the time, but future studies show that it causes HCM. Also, further genetic testing might be recommended to include any newly identified genetic changes that cause HCM that were not included in earlier testing.

How do I know if I have HCM?

If genetic testing shows that you have the genetic change for HCM, you will need to see a cardiologist (heart doctor) to check your heart for signs of HCM. If the genetic change that causes HCM in your family is not known, parents, siblings, and children of the person with HCM will need to be checked for signs of HCM. Cardiologists can diagnose HCM using

Knowing the symptoms of HCM is important if you have a family health history of HCM, especially if you have the genetic change for HCM that runs in your family. Even if you don’t have a family health history of HCM, tell your doctor if you have any of the following common symptoms of HCM:

  • Feeling tired or lacking energy
  • Shortness of breath, especially with physical activity
  • Chest pain, especially with physical activity
  • Fainting or feeling dizzy or lightheaded
  • Swelling in the ankles, feet, legs, or stomach

Some people with HCM do not have symptoms in the early stages but develop them over time. Thus, even if you do not currently have signs or symptoms of HCM, you might need repeated monitoring based on your age and other factors if you have a family health history of HCM, especially if you have the genetic change for HCM that runs in your family.7 Let your doctor know right away if you develop any of the symptoms of HCM.

What can I do if I or my child has HCM?

If you or your child has HCM, the doctor may recommend

  • Regular monitoring: Adults need to see a cardiologist (heart doctor) every 3-5 years to look for changes in the heart using echocardiogram, electrocardiogram (ECG), and checking for symptoms of HCM. For children and teens, the interval is every 1-3 years. 6
  • Medication: Currently, no medicines have been proven to prevent HCM or lower the chances of dying. However, a variety of medicines can be used to treat symptoms of HCM. New drugs are currently being tested in clinical trials that may help patients with HCM.
  • Light to moderate physical activity: Light to moderate physical activity has been shown to help those with HCM. Those engaging in very high intensity activities such as competitive sports should discuss their risk with an HCM-trained specialist.
  • Surgery: Your doctor might recommend surgery if you have severe HCM.
  • Controlling other chronic conditions: High blood pressure, sleep apnea, and being overweight or having obesity can increase your risk of developing complications of HCM. Making lifestyle changes and taking other steps to manage these conditions are important for people with HCM.

While these steps cannot prevent HCM, they can help keep your heart as healthy as possible and decrease your likelihood of developing complications.


  1. McKenna WJ, Judge DP. Epidemiology of the inherited cardiomyopathies. Nat Rev Cardiol. doi:10.1038/s41569-020-0428-2
  2. Hypertrophic Cardiomyopathy (HCM), American Heart Association. Accessed August 15, 2022.
  3. Hypertrophic Cardiomyopathy, Cardiomyopathy UK. Accessed August 15, 2022.
  4. Maron BJ. Clinical Course and Management of Hypertrophic Cardiomyopathy. New England Journal of Medicine. 2018;379(7):655-668.
  5. Ho CY, Day SM, Ashley EA, et al. Genotype and Lifetime Burden of Disease in Hypertrophic Cardiomyopathy: Insights From the Sarcomeric Human Cardiomyopathy Registry (SHaRe). Circulation. 2018;138(14):1387. doi:10.1161/CIRCULATIONAHA.117.033200
  6. Ommen SR, Mital S, Burke MA, et al. 2020 AHA/ACC Guideline for the Diagnosis and Treatment of Patients With Hypertrophic Cardiomyopathy. Circulation. 2020;142(25):E558-E631. doi:10.1161/CIR.0000000000000937
  7. Cirino AL, Ho C. Hypertrophic Cardiomyopathy Overview. GeneReviews®. Published online July 8, 2021. Accessed August 29, 2022.
  8. Gimeno JR, Olivotto I, Rodríguez AI, et al. Impact of SARS‐Cov‐2 infection in patients with hypertrophic cardiomyopathy: results of an international multicentre registry. ESC Heart Fail. 2022;9(4):2189. doi:10.1002/EHF2.13964
  9. Blausen.com staff (2014). “Medical gallery of Blausen Medical 2014“. WikiJournal of Medicine 1 (2). DOI:10.15347/wjm/2014.010ISSN 2002-4436