How Hypertrophic Cardiomyopathy Is Diagnosed

Hypertrophic cardiomyopathy (HCM) is an inherited condition in which the heart muscle is thickened, leading to possible complications. HCM may be first suspected based on the identification of a heart murmur or other abnormalities on testing or a physical exam.

Cardiac imaging with echocardiogram or cardiac magnetic resonance imaging (MRI) is used to diagnose HCM. These noninvasive tests measure heart wall thickness and evaluate any associated blood flow obstruction or valvular problems that often accompany HCM. Genetic blood testing may also be used.

This article discusses the process for diagnosing HCM.

Heart ultrasound

Pitchayanan Kongkaew / Getty Images

Physical Examination

A healthcare provider may suspect hypertrophic cardiomyopathy if they hear a heart murmur during a physical examination. By using a stethoscope, healthcare providers can listen for heart valve closures, murmurs, or other abnormal sounds.

What Is a Heart Murmur?

A heart murmur is a sound created by turbulence of blood flow. Murmurs may be harmless or serious. Causes include narrow or leaky heart valves, congenital defects in the heart's walls (septal defects), pregnancy, and anemia.

A healthcare provider can perform certain maneuvers during the physical exam to differentiate between a harmless murmur and HCM murmur:

  • Position changes: A murmur that gets louder from squatting to standing position is concerning for HCM.
  • Valsalva maneuver: A murmur that gets louder with the Valsalva maneuver (bearing down like having a bowel movement) is concerning for HCM.

Other physical exam findings that are suggestive of HCM include arterial pulse and apical pulse abnormalities.

Whenever abnormalities that suggest HCM are detected upon a physical examination, your healthcare provider will ask about any related symptoms. These include:

  • Exercise intolerance
  • Shortness of breath
  • Chest pain
  • Dizziness
  • Fainting
  • Palpitations

If your healthcare provider suspects HCM, they will ask about family history, including history of:

  • Sudden cardiac death
  • Unexpected death at a young age
  • Heart failure
  • Heart valve problems

You should provide details not just of first-degree relatives, like siblings or parents, but also about cousins, aunts, uncles, grandparents, and great-grandparents. Questions about the heart health of family members is especially important in HCM, since this condition is inherited.

Electrocardiogram

An electrocardiogram (ECG) can provide clues about an HCM diagnosis. This test may be performed for another reason and be the first indication that HCM is present.

The ECG provides information about the heart rhythm as well as chamber size and heart wall thickness. In very thick-walled hearts, the ECG may be significantly abnormal, but the findings are not very specific. The findings may be due to many causes, including:

Follow-up testing with heart imaging is required to differentiate these conditions and diagnose HCM.

Echocardiogram

Transthoracic echocardiography (called "echo" for short) is a noninvasive test that uses an ultrasound to produce pictures of the heart.

During this procedure, an ultrasound technician will take pictures from the surface of your chest using a wand and gel. You may be asked to hold your breath for a few seconds or change position in order to get the best pictures.

In addition to providing pictures of the heart, echocardiography also includes information about blood flow and can show the following possible complications of HCM:

  • Obstruction of blood flow from the heart to the aorta due to the thickened heart muscle
  • Mitral regurgitation, or leakage of the mitral valve that separates the left-sided chambers of the heart
  • Aneurysms, or outpouchings, in the wall of the left ventricle
  • Weakened heart muscle

People who are found to have HCM will initially require repeat echocardiograms every year or two to monitor the heart's function, wall thickness, and valves.

Cardiac MRI

Like echocardiography, cardiac MRI also provides pictures and information about blood flow in the heart and is used to diagnose HCM.

MRI is a painless, noninvasive test that uses a strong magnet to create images. Note that the cardiac MRI machine can be loud, and some people experience claustrophobia during this test.

MRI may also be used after HCM is diagnosed to evaluate for scar tissue. When a significant amount of scar tissue is present, the risk of sudden cardiac death increases. This information can be used by cardiologists when deciding whether or not to recommend an implantable cardioverter defibrillator (ICD) as a treatment.

Why Would an ICD Be Needed in HCM?

One of the most devastating complications of HCM is sudden cardiac death. ICDs are a type of implantable device that monitor the heart's rhythm and can provide a shock of electricity to stop any dangerous heart rhythms like ventricular tachycardia or ventricular fibrillation. Cardiologists take into account several factors when recommending whether or not someone with HCM should consider getting an ICD. These include symptoms like fainting, family history of sudden cardiac death, findings from echocardiography or MRI, and findings on heart rhythm testing.

Genetic Testing

HCM is an inherited condition that can be caused by mutations in several genes related to the sarcomere, a component of the heart muscle. While there are several known genes that cause HCM, 40% of people with HCM don't have a mutation in one of the known genes. Therefore, getting a genetic test that does not identify a known HCM-causing mutation does not mean a person does not have HCM.

Even though the diagnosis of HCM doesn't rely on genetic testing, this type of testing is very important for screening family members. If a mutation is identified in someone with HCM, screening relatives is simplified, since they only need a blood test to determine if they have HCM or not.

If no mutation is found in the affected person with HCM, family members will need to undergo periodic echocardiograms to see if they develop HCM.

Additional Testing

Once HCM is diagnosed, more cardiac tests need to be done to optimize the treatment of HCM or determine if an implantable cardioverter defibrillator (ICD) is appropriate.

Exercise Stress Testing

During exercise stress testing, you will be asked to walk on a treadmill or ride a stationary bicycle while your heart rhythm is monitored with an ECG. After you have exercised as long as possible, you will be asked to lay on a table where images of the heart are taken with an echocardiogram.

This test is performed in people with HCM to look for obstruction to the blood flow out of the heart. People with HCM may have intermittent symptoms from obstruction.

An echocardiogram done while at rest may not show obstruction, but with exercise, the heart is contracting more vigorously, and an obstruction may be provoked.

Heart Rhythm Testing

Heart rhythm testing is performed to evaluate the heart's rhythm over a period of days to weeks. A device, such as a Holter monitor, is worn for a specified period. Then, a cardiologist interprets the results.

Cardiologists are interested in whether or not any arrhythmias occurred. The presence of ventricular tachycardia is a marker of increased risk for sudden cardiac death and is one indication for placement of an ICD.

Differential Diagnosis

HCM is just one cause of a thickened heart muscle. The following can also cause thickened heart muscle.

  • High blood pressure
  • Aortic stenosis
  • Cardiac amyloidosis
  • Fabry disease

Another possible cause is known as "athlete's heart." Just as exercise affects skeletal muscles, it can cause changes in the heart muscle. Athlete's heart has specific findings, including that the thickened heart muscle goes away after stopping intense exercise.

Differentiating between these and HCM as causes of the thickened heart muscle is essential for proper treatment.

Summary

HCM is an inherited condition causing thickening of the heart muscle. While findings during a physical examination and an electrocardiogram may be suggestive, HCM is never diagnosed by these alone. It requires heart imaging with either an echocardiogram or cardiac MRI. Other cardiac tests, like exercise stress testing and heart rhythm monitoring, can be useful in the management of HCM. Genetic testing is useful for screening family members.

A Word From Verywell

Undergoing tests to diagnose heart conditions can be stressful, particularly when the potential diagnosis can be frightening. Thankfully, our understanding of HCM has come a long way. There are medical and surgical treatments to improve symptoms and quality of life and ways to prevent complications like sudden cardiac death. Always contact a healthcare provider for an examination if you experience any symptoms of a heart condition.

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