A racing, fluttering, or skipped heartbeat can feel unsettling, especially if you’re living with hypertrophic cardiomyopathy (HCM). This condition can affect both the structure and the electrical signals of the heart, which may raise the chance of abnormal heart rhythms, known as arrhythmias.

For people with HCM, finding and treating arrhythmias is an important part of protecting heart health and reducing the risk of serious complications. This article explains why HCM and arrhythmias are connected, which rhythm problems are most common, how doctors diagnose them, and which treatments may help.

Why Are People With HCM at Higher Risk of Arrhythmias?

HCM causes part of the heart muscle to become thicker than usual. In many people, the thickening affects the left ventricle, the heart’s main pumping chamber.

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HCM can also cause other changes inside the heart muscle. One change linked to heart arrhythmias is myofiber disarray, which means the heart muscle cells are arranged in an abnormal pattern. HCM can also lead to fibrosis, or scar tissue, in the heart muscle.

These changes can disrupt the flow of electrical signals through the heart. When those signals don’t travel normally, an arrhythmia can develop.

Which Arrhythmias Are Common With HCM?

Although there are many types of arrhythmias, people with HCM are most likely to develop atrial fibrillation (AFib) and ventricular arrhythmias.

Atrial Fibrillation

Atrial fibrillation starts in the atria, the heart’s two upper chambers. During AFib, these chambers beat rapidly and unevenly.

AFib is common in people with HCM. Research shows that more than 25 percent of people with HCM have AFib. Some people have no symptoms, while others may experience:

• Palpitations (noticeable heartbeat changes, such as a racing, fluttering, or pounding heart)
• Shortness of breath
• Chest pain
• Fatigue
• Dizziness
• Reduced ability to exercise

AFib can also raise the risk of blood clots. If a clot travels to the brain, it can cause a stroke.

Ventricular Arrhythmias

Ventricular arrhythmias start in the ventricles, the heart’s two lower chambers. One type is ventricular tachycardia, which causes the ventricles to beat too fast. Doctors monitor this arrhythmia closely because it can become dangerous.

Like AFib, ventricular tachycardia may not cause symptoms. However, symptoms are more common and can be more serious. They include:

• Fainting
• Palpitations
• Shortness of breath
• Chest pain
• Fatigue
• Dizziness

A type of ventricular arrhythmia called nonsustained ventricular tachycardia (NSVT) occurs when the fast heart rhythm stops on its own after a short time.

What Can Raise the Risk of Arrhythmias in HCM?

Your doctor may look for factors that can increase your risk of developing an arrhythmia. According to the journal Circulation, risk factors may include:

• Older age
• Male sex
• Obesity
• High blood pressure
• A family history of arrhythmias

How Do Doctors Detect and Monitor Arrhythmias in HCM?

During a physical exam, your doctor may listen for a heart murmur, an unusual sound heard through a stethoscope.

In some people with HCM, a murmur can occur when thickened heart muscle affects blood flow out of the heart. Doctors may also hear an irregular heartbeat. If so, they may order tests such as an electrocardiogram (ECG), echocardiogram, or cardiac MRI to learn more.

Heart Rhythm Tests

An ECG records the heart’s electrical activity during a short test. It can detect arrhythmias and is commonly used to diagnose and monitor HCM. An ECG is usually recommended during the initial evaluation and every one to two years afterward.

Because arrhythmias can come and go, doctors may also recommend ambulatory ECG monitoring. This may involve a Holter monitor or another wearable device that records your heart rhythm as you go about your day. The 2024 HCM guidelines recommend 24 to 48 hours of ambulatory monitoring.

Tell your doctor if symptoms happen during exercise, sleep, or daily activities. Details about timing can help your care team choose the right type of monitor and decide how long you may need to wear it.

Imaging Tests

An echocardiogram uses ultrasound to show heart muscle thickness, pumping function, and blood flow. It can also help doctors determine whether thickened heart muscle is blocking blood flow out of the heart.

A cardiac MRI provides more detailed images and may show fibrosis in the heart muscle. This information can help guide treatment and long-term care decisions.

How Are HCM-Related Arrhythmias Treated?

Treatment depends on the type of arrhythmia and your symptoms, test results, and overall risk. Your care team may recommend medication, procedures, implantable devices, or a combination of treatments.

Medications

Medications may help relieve symptoms. Common options include:

• Beta-blockers — These drugs are often recommended for people with obstructive HCM, which means thickened heart muscle makes it harder for blood to leave the heart. They slow the heart rate and help improve chest discomfort, shortness of breath, and palpitations.
• Calcium channel blockers — These medications also slow the heart rate and help the heart relax between beats. Doctors may recommend them if beta-blockers don’t help enough or cause side effects that are hard to manage.
• Anticoagulants — These medications help prevent blood clots. They’re often recommended for people with HCM and AFib because AFib increases the risk of stroke.
• Cardiac myosin inhibitors — These drugs may be prescribed for obstructive HCM.

Ablation

Catheter ablation is a procedure that uses a thin tube to find and block small areas of heart tissue that send abnormal electrical signals. These signals can lead to AFib. Some people may need more than one ablation procedure or may still need medication afterward.

AFib treatment is a common topic among MyHeartDiseaseTeam members. “I had a successful ablation three years ago next month. I was in the hospital at 6 a.m., prepped before 8, out and walking the halls before noon, and discharged before 5 p.m., feeling good,” one member said. “I’m drug-free, and I haven’t had a single AFib event since.”

Implantable Devices

An implantable cardioverter-defibrillator (ICD) is a small device that monitors heart rhythm. An ICD can deliver treatment if a dangerous rhythm occurs. Doctors may recommend an ICD for some people with HCM who are at risk of life-threatening arrhythmias.

ICDs aren’t recommended for everyone with HCM. Instead, doctors review risk factors, monitoring results, and imaging findings to estimate risk and support shared decision-making.

What Should You Ask Your Doctor?

Arrhythmia care in HCM is individualized. A treatment plan that works for one person may not be right for another. Shared decision-making can help ensure your care reflects your needs and preferences.

You may want to ask:

• Have I had AFib, ventricular tachycardia, or NSVT on heart monitoring?
• How often should I have rhythm monitoring?
• Do I need medication to help prevent blood clots?
• What is my risk of a life-threatening heart rhythm?
• Would I benefit from seeing a heart rhythm specialist?

Regular follow-up visits can help your care team detect heart rhythm changes early and adjust your treatment plan as needed.

Join the Conversation

On MyHeartDiseaseTeam, people share their experiences with heart disease, get advice, and find support from others who understand.

Have you had heart rhythm monitoring or treatment for HCM-related arrhythmias? Let others know in the comments below.