Overview

What Is Hypertrophic Cardiomyopathy?

What Is Hypertrophic Cardiomyopathy?

Hypertrophic cardiomyopathy (HCM) affects one in 500 people in the general population. In most cases, HCM is caused by genetic mutations.

Doctors usually discover HCM during cardiac testing (an electrocardiogram or echocardiogram). During this test, doctors see thickening (hypertrophy) on the heart’s left lower chamber (ventricle), even though the patient has no other disease that could cause this thickening.

Most patients with left ventricular hypertrophy have heart cells that are larger than normal. These larger cells cause the heart's lower chambers, usually the left chamber (ventricle), to become thick and stiff. But the location and amount of thickening can be very different for each person. Because of this, HCM can be hard to diagnose.

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Symptoms of HCM

Symptoms of HCM are different depending on how old you are. Most patients with HCM don’t have many symptoms. For this reason, a doctor may discover HCM during a routine appointment for other issues. Some patients with HCM have cardiac arrhythmias (irregular heartbeat), heart failure symptoms, or sudden cardiac death.

Early Stage Symptoms

In the early stages of HCM, you may experience any of the following:

  • Chest discomfort
  • Shortness of breath
  • Fatigue
  • Palpitations
  • Fainting or dizziness (particularly with exercise)

Over time, HCM can get worse and cause heart failure with symptoms of shortness of breath, chest discomfort, and edema. HCM can also cause atrial fibrillation, which increases your chances for stroke. In addition, HCM can cause sudden cardiac death because of ventricular arrhythmias (abnormal rapid heartbeats).

Genetics & HCM

Hypertrophic cardiomyopathy (HCM) is the most common genetic heart (cardiac) condition. It affects more than 1 in 500 people in the US. 

Genetic counseling and genetic testing can be helpful so you can learn more about your family’s risk (chances) of inheriting this condition.

DNA is the genetic material that provides instructions for what our bodies look like and how they work. Within our DNA we have over 20,000 genes. Each of these genes contain hundreds to thousands of DNA bases (A, T, C, and G), which spell out the code for a unique protein and have a unique role in your body.

What Genetic Mutation Causes Hypertrophic Cardiomyopathy?

Currently, there are 26 genes that have been associated with HCM. Two of the most common are called: 

  • MYH7and 
  • MYPBC3

We have two copies of each of these genes (one inherited from mom and the other from dad). HCM is caused when there is a disease-causing genetic change (mutation) in one copy of any one of these genes.

HCM is most commonly an autosomal dominant condition. This means that a person only needs one non-working copy of the gene in question to have HCM.

People with HCM have an underlying genetic change in these DNA bases (called a mutation). These mutations cause their heart muscles to develop abnormally.

For people with HCM, there is a 50% chance that each first-degree relative (parents, siblings, and children) also inherited the genetic mutation that causes HCM. 

Can Genetic Testing Detect HCM?

Genetic testing can’t always detect the mutations that cause HCM. Doctors are learning more about the genes involved, but we know we haven’t identified every single gene that can cause HCM. 

For this reason, the percentage of time we are able to find a genetic change in an individual with HCM (also called the detection rate) is not 100%. We detect about 60% of the mutations (genetic changes) responsible for HCM.

Simply having a mutation that’s known to cause HCM doesn’t automatically mean you’ll develop the disease. Often times, people who have the same mutation known to cause HCM can have different presentations of the disease, even among family members. This means that not everyone with the HCM mutation will develop HCM.

Should I Get Screened for HCM?

If your family member has HCM and if your family member has a mutation that causes HCM, your family member’s children and siblings can get genetic testing. Genetic testing can help find these children’s and siblings’ chances of developing HCM.

Genetic testing can also help children and siblings know how often they should get a heart screening.

If children and siblings test negative for the HCM mutation, this means they do not have higher chances (increased risk) of developing hypertrophic cardiomyopathy or for passing it onto their children They also don’t need regular HCM screening. 

Sometimes people with HCM don’t seem to have any of the genetic mutations that cause HCM. In these cases, all first-degree relatives of the person with HCM should have non-invasive heart (cardiac) screening, starting in childhood. 

  • First-degree relatives should continue getting cardiac screening every year during their teen years, and then every 3—5 years after that.
  • Your cardiologist will also make recommendations for how often you should be screened.

How Is Hypertrophic Cardiomyopathy Diagnosed?

View Image Figures A & B:
Figure A shows a normal patient's
heart; figure B shows a patient's
heart with hypertrophic
cardiomyopathy.

Doctors often diagnose HCM by using noninvasive cardiac imaging, including echocardiography and/or cardiac magnetic resonance imaging. To diagnose HCM, doctors will look at a patient’s left ventricle (lower heart chamber). If the patient’s left ventricle is hypertrophied or thickened (usually ≥15 mm wall thickness), and if the patient doesn’t have cardiac disease or another disease that causes ventricle thickening, the patient may have HCM.

Inherited Disorder

HCM is inherited in an autosomal dominant pattern. This means that people with HCM have a 50 percent chance of passing this condition on to their children. Genetic researchers have identified over 1,500 mutations affecting more than 15 genes associated with HCM.

HCM can also be identified through family history and molecular genetic testing. These tests accurately diagnose HCM in a patient. They can also identify if a patient’s relatives have the HCM mutation.

You can have genetic testing for HCM with a blood sample. The test is covered by most insurance policies.

Treatment

Treating patients with HCM is guided by how severe symptoms are, whether a patient has any risk factors for sudden cardiac death, and whether a patient has cardiac arrhythmias and other associated problems. Treating patients with HCM is typically coordinated by a multidisciplinary team and includes the following goals:

  • Treating symptoms
  • Doing a risk assessment and preventing sudden cardiac death
  • Making recommendations for physical activity
  • Managing comorbidities (e.g. hyperlipidemia, coronary artery disease, or sleep apnea)
  • Testing first degree relatives to see if they have the HCM mutation

Treating Symptoms

Most patients with HCM have minor to no symptoms. If your doctors determine that you have a low risk of sudden cardiac death, you won’t need treatment.

For patients who have symptomatic obstructive HCM (OHCM), the first treatment is medical therapy. Medical therapy for HCM includes using beta-blocker or a non-dihydropyridine calcium channel blocker. In patients with persistent obstruction, disopyramide is a safe and effective way to relieve obstruction and improve symptoms.

 

Patients who have OHCM symptoms that don’t get better with medical therapy will benefit from septal reduction therapies (i.e. septal myectomy or alcohol septal ablation). Septal myectomy is a surgical procedure where doctors cut out (excise) part of the hypertrophied (thickened) and asymmetric heart wall (also called the septum). Septal myectomy is considered the gold-standard approach for septal reduction.

Alcohol Septal Ablation

Sometimes patients have OHCM symptoms that don’t improve with medical therapy. Some of these patients are considered too high-risk to have surgery, or they simply prefer not to have surgery. For these patients, doctors can perform a catheter-based percutaneous alcohol septal ablation is an alternative.

Alcohol septal ablation is a procedure that tries to decrease the thickness of the septum (heart wall). To do this, doctors safely induce a myocardial infarction (heart attack) in a controlled setting. Doctors perform this procedure in our cardiac catheterization lab.

In patients with non-obstructive HCM, symptoms are generally treated with medical therapy. This is because patients who don’t have obstruction don’t need to have their septum thinned. Some patients with HCM may develop end-stage heart failure. These patients may need heart transplant surgery.

Preventing Sudden Cardiac Death

Fortunately, sudden cardiac death that happens because of ventricular arrhythmias is a rare for patients with HCM. Our multidisciplinary team will assess each patient’s risk for cardiac death using population studies.

American and European guidelines and calculators were created to estimate the risk of sudden death in HCM. But unfortunately, the accuracy of these risk models isn’t perfect. Doctors recommend an implantable cardioverter defibrillator (ICD) in patients who have a higher chance of having sudden cardiac death. An implantable cardioverter defibrillator (ICD) will pace or shock a patient’s heart if they have a life-threatening arrhythmia.

Recommendations for Physical Activity

Participating in competitive or high-intensity athletics is considered risky for sudden cardiac death in patients with HCM. For this reason, doctors discourage patients with HCM from playing sports. Patients are allowed to practice low-impact recreational sports. However, it’s important for patients to always self-limit their activity (or rest whenever they feel the need to do so).

Patients should plan their individual exercise program with their doctor so that all factors can be taken into consideration.

Managing Comorbidities

Patients with HCM have higher chances of developing other heart conditions (called comorbidities). These include:

  • hyperlipidemia,
  • coronary artery disease, and
  • hypertension.

Doctors treat these conditions according to current guidelines and heart research.

Testing First Degree Relatives

We recommend that first degree relatives receive testing and diagnostic evaluation for HCM. Our doctors will perform genetic testing or electrocardiograms and echocardiograms based on the relative’s age.

Comprehensive, Expert Care for Treating HCM

The Hypertrophic Cardiomyopathy (HCM) Program at University of Utah Health is the first in the state of Utah and one of the nation’s few comprehensive programs for evaluating and managing HCM. The program offers a comprehensive evaluation by experts in:

We understand that hypertrophic cardiomyopathy is a complex disease. By bringing doctors from multiple specialties together, we can provide leading-edge evaluation and a therapeutic plan that best suits your individual needs.

Contact Us

For more information, call or email us:
Phone: 801-585-5122
Email: hcm@hsc.utah.edu