Diagnostic Testing
Tests and genetics help diagnose HCM
The HCM conversation with your doctor can be started for many reasons. You may be having symptoms; your doctor may have heard a heart murmur during a physical exam or seen something abnormal during an electrocardiogram (EKG); or you may have just learned you have a family history of HCM. Regardless of what brings you to see your doctor, be aware that the amount of time needed to determine an HCM diagnosis may vary.
Symptoms linked to HCM may be caused by other conditions, such as high blood pressure or a narrowed aortic valve (aortic stenosis). Because of this, you will likely undergo a variety of tests as your doctor rules out other possible problems before making a diagnosis.
Most often a cardiologist will be the specialist to diagnose your condition. Ideally, that cardiologist will be an HCM specialist. If not, consider getting a second opinion from an HCM specialist or at a center known for treating HCM.
After reviewing your medical history, family medical history and your lifestyle habits, your doctor will begin the exams and testing needed to diagnose or rule out HCM.
Physical Examination
Your doctor will listen to your heart and lungs with a stethoscope. The loudness, timing and location of a heart murmur may point to HCM. A crackling sound in the lungs may be a sign of heart failure — when the heart cannot pump well enough to meet your body’s demands.
Diagnostic Tests and Procedures
One or more of the following may be used to diagnose or monitor your condition.
Cardiac catheterization. This checks the pressure and blood flow in the chambers of your heart. Your doctor inserts a catheter (a thin, flexible tube) through a blood vessel into your heart. This allows the doctor to collect blood samples and check for heart blockages.
Cardiac computed tomography. This may be an option if an echocardiogram cannot confirm HCM and an MRI cannot be done, but your doctor continues to suspect HCM.
Cardiac magnetic resonance imaging (MRI). This special imaging technique may be used in the following instances:
- An echocardiogram cannot confirm the diagnosis.
- Extra information is needed about the amount and location of thickening or about the anatomy of the mitral valve.
- Placement of an implantable cardioverter defibrillator (ICD) is being considered.
Chest X-ray. This X-ray can show whether your heart is enlarged or fluid has built up in your lungs.
Coronary angiography. Dye is injected into your coronary arteries, which allows your doctor to view blood flow on an X-ray. This procedure is often done during cardiac catheterization.
Echocardiogram (echo). An echo is often key for diagnosis. It uses sound waves to create a picture of your heart in action. It can show how well your heart is working, including how blood flows from your heart. It also shows your heart’s size and shape, as well as its muscle thickness.
Another type of echocardiogram called a transesophageal echo (TEE) is sometimes used. It provides a view of the back of your heart. It can also be used to assess your mitral valve and to monitor the results of surgery to lessen heart thickening (myectomy), if it has been performed.
Electrocardiogram (EKG). This test records your heart’s electrical activity. It can show the rhythm of your heart and how fast it is beating. In addition, an EKG can detect a heart attack, heart failure and arrhythmias. To track problems that may come and go, your doctor may have you wear a portable EKG at home.
Event monitor. This portable device is a self-activated monitor that records your heart’s electrical activity. You will wear the monitor until the number of recordings your doctor requests take place.
Genetic tests. These tests cannot predict whether you will develop symptoms or your long-term outlook, but they can show whether HCM runs in your family.
Holter monitor. This wearable device continuously records your heart’s electrical signals for 24 to 48 hours to capture arrhythmias.
Myocardial biopsy. The doctor removes a bit of heart muscle to view under a microscope for signs of changes that suggest HCM. The biopsy may also be taken during cardiac catheterization.
Stress test. This test checks how your heart responds to stress while other tests are being done. You walk on a treadmill or take special medication to make your heart beat faster. Despite its name, a stress test is safe and can help your doctor know how much your condition is keeping you from being active.
This test may also include an echocardiogram, positron emission tomography (PET) or nuclear heart scan. A PET myocardial perfusion imaging scan, commonly known as a PET stress test or a Rubidium PET, shows how well blood flows to your heart’s muscles while you are at rest and during stress. A nuclear heart scan involves injecting a radioactive substance into a vein then taking pictures of the blood flowing in and around the heart.
The Role of Genetics in HCM
You may wonder what you have or haven’t done to get HCM. The answer is nothing. If you have HCM, it is likely that one of your parents has or had the condition. The most common cause is abnormal genes (mutations) that are inherited, or passed down, through families. This is known as familial hypertrophic cardiomyopathy.
Familial HCM is passed down in an autosomal dominant pattern. This means the mutated gene is on a non-sex chromosome. Only a single copy of this gene is needed in each cell to cause the disease. Rarely, you may have a mutation in both copies of the mutated gene. If that is the case, the signs and symptoms of HCM are more severe.
Certain genes give the body instructions to make proteins that play important roles in the contraction of the heart muscle, which is needed to pump blood to the rest of the body. Mutations of these genes are thought to lead to the abnormal structure or function of certain cell components within muscles called sarcomeres (SAR-kuh-meers) that allow the heart to contract. These abnormal or mutated genes in the heart muscle cause the walls of the heart chamber (left ventricle) to contract harder and become thicker than normal (hypertrophy). Changes in heart muscle fibers may happen even before the muscle thickens or symptoms show up.
Several mutations are known to be associated with HCM. The most commonly involved genes are MYBPC3, MYH7, TNNI3 and TNNT2. A mutation in any of these genes can lead to HCM.
Genetic testing is performed using a sample of saliva or blood. Multi-gene panels are used to identify the presence of these and other known mutations. During testing, DNA is extracted from the blood to analyze 30 to 50 genes for the known mutations linked to HCM. Experts believe more research is needed to identify more mutations, so it is possible that your testing may not indicate HCM. However, it is important to keep your doctor aware of your condition for ongoing monitoring and testing.
A referral to a genetic counselor, either on staff or elsewhere, is highly encouraged. The genetic counselor can help you understand the often-complicated test results and what they mean for you and for your family members and their future health.
If results show that you have an HCM mutation, testing for that same mutation is recommended for your first-degree relatives (parents, children and siblings). By sharing this valuable information, you are giving them the opportunity to follow up with their doctors and take appropriate precautions. Many people do not realize they have HCM until something life-threatening or life- ending occurs, and knowing they may be at risk could potentially be lifesaving.
Finding cardiac conditions early
In an effort to identify undiagnosed abnormal heart conditions in young people, comprehensive heart screening programs are becoming more widespread across the U.S. These screenings are not just for student athletes; rather, they are designed for any young person between the ages of 8 and 25 who has not already been identified as at-risk for HCM or other heart-related issues.
To reach the desired demographic, many programs are partnering with school districts and other organizations to offer mobile cardiac screenings to middle school, high school and college students. It is important to note, however, that one screening does not last a lifetime. As people age, certain conditions can develop, so follow-up screenings every couple of years until age 25 are recommended.
One such program, In A Heartbeat (inaheartbeat.org), was created by Mike Papale. At 17, he experienced sudden cardiac arrest (SCA). A nearby volunteer EMT’s quick action prevented Mike from experiencing sudden cardiac death (SCD). Today, he lives a healthy life in spite of a hypertrophic cardiomyopathy (HCM) diagnosis, and he works hard to prevent others from having similar life-threatening situations by raising awareness about SCA and HCM, and promoting the importance of CPR and automated external defibrillators (AEDs).
“We hold cardiac screening programs for kids ages 8 to 22,” Mike explained. “We have volunteers, including my pediatric cardiologist, and other medical personnel on site to read the EKGs. If a problem is detected, they sit down and talk about it with the parents. We also provide AEDs and emergency training to organizations. You can’t prevent HCM, but with a little knowledge, you can manage it.”
About HCM-related SCD
Sudden cardiac death (SCD) is caused by a cardiovascular condition. During periods of strenuous exertion and/or dehydration, the degree of obstruction to blood flow progresses and can prevent the heart from pumping blood to the rest of the body, including to the heart. It can cause the heart to stop, resulting in death.
In athletes under 35 years old, HCM is the leading cause of SCD. However, not all cases of SCD are caused by HCM, and most people with HCM are considered low risk for it. Learning about the risks for HCM-related SCD and the preventive measures can be lifesaving.
Telling your doctor whether any of the following apply to you may help prevent a serious episode or early death:
- A family history of SCD, such as a first-degree relative (a parent, sibling or child) with HCM
- Several episodes of fainting
- An abnormal blood pressure response with exercise
- A history of arrhythmia with a fast heart rate
- Severe HCM symptoms and poor heart function
