What is HCM? Understanding Hypertrophic Cardiomyopathy

Hypertrophic Cardiomyopathy

Hypertrophic cardiomyopathy (HCM) is a condition characterized by the thickening of the heart muscle. This thickening, or hypertrophy, can occur in various parts of the heart, but most commonly affects the septum, the muscular wall separating the heart’s two lower chambers (ventricles). While this thickening can happen anywhere in the left ventricle, it’s crucial to understand what this condition entails and how it impacts heart function.

In essence, hypertrophic cardiomyopathy (HCM) is a disease where the heart muscle becomes abnormally thick. This thickened muscle can make it harder for the heart to effectively pump blood throughout the body. Many individuals with hypertrophic cardiomyopathy are unaware they have it because they may experience few or no noticeable symptoms. However, for some, HCM can lead to significant symptoms such as shortness of breath and chest pain. Furthermore, HCM can sometimes disrupt the heart’s electrical system, potentially causing life-threatening irregular heartbeats (arrhythmias) or even sudden cardiac death.

Symptoms of HCM

The symptoms of hypertrophic cardiomyopathy can vary widely from person to person. Some individuals may experience no symptoms at all, while others may have one or more of the following:

• Chest pain, often occurring during physical exertion or exercise. This pain can be due to reduced blood flow to the heart muscle itself.
• Fainting or lightheadedness, particularly during or immediately after exercise or any form of physical activity. This can be a result of reduced blood flow to the brain.
• Palpitations, which are sensations of rapid, fluttering, or pounding heartbeats. These irregular rhythms can be caused by the altered heart muscle and electrical pathways.
• Shortness of breath, especially during exercise or exertion. This symptom arises from the heart’s reduced ability to pump blood effectively to meet the body’s oxygen demands.

When to Seek Medical Advice

It’s important to note that symptoms like shortness of breath and palpitations can be associated with various medical conditions. Therefore, if you experience these symptoms, seeking prompt medical evaluation is crucial to determine the underlying cause and receive appropriate care. Specifically, if you have a family history of HCM or are experiencing any symptoms suggestive of hypertrophic cardiomyopathy, consult with your healthcare professional.

Emergency Symptoms:

Call emergency services immediately (911 in the US or your local emergency number) if you experience any of the following symptoms lasting for more than a few minutes:

• Rapid or irregular heartbeat: This could indicate a serious arrhythmia.
• Trouble breathing: Severe shortness of breath can be a sign of significant heart distress.
• Chest pain: Persistent or severe chest pain needs immediate medical attention.

Causes of HCM

Hypertrophic cardiomyopathy is primarily a genetic condition. In most cases, HCM is caused by genetic mutations that affect the heart muscle proteins, leading to the thickening of the heart muscle.

HCM often affects the septum, the wall separating the two ventricles. This thickening can obstruct the flow of blood leaving the heart, a condition known as obstructive hypertrophic cardiomyopathy.

In other cases, the thickening doesn’t significantly block blood flow; this is referred to as nonobstructive hypertrophic cardiomyopathy. However, even without obstruction, HCM can cause the left ventricle, the heart’s main pumping chamber, to become stiff. This stiffness impairs the heart’s ability to relax and fill with blood properly between beats. Consequently, the ventricle holds less blood and pumps less blood out to the body with each heartbeat.

Furthermore, in HCM, the heart muscle cells can become disorganized, a phenomenon called myofiber disarray. This disarray can disrupt the normal electrical signals in the heart, predisposing individuals to irregular heartbeats.

Risk Factors for HCM

The most significant risk factor for hypertrophic cardiomyopathy is family history. HCM is typically inherited, meaning it is passed down genetically through families. If a parent has hypertrophic cardiomyopathy, there is a 50% chance that their children will inherit the gene mutation that causes the disease.

Given this hereditary nature, it is crucial for parents, children, siblings, and other close relatives of individuals diagnosed with hypertrophic cardiomyopathy to discuss genetic screening and appropriate testing with their healthcare providers to assess their risk.

Complications of HCM

Hypertrophic cardiomyopathy can lead to several potential complications, some of which can be serious:

• Atrial Fibrillation (AFib): The thickened heart muscle and structural changes at the cellular level can increase the risk of atrial fibrillation, an irregular and often rapid heartbeat. AFib also elevates the risk of blood clot formation, which can travel to the brain and cause a stroke.
• Blocked Blood Flow (Outflow Obstruction): In many individuals with HCM, the thickened heart muscle obstructs the outflow of blood from the heart. This obstruction can lead to symptoms like shortness of breath during activity, chest pain, dizziness, and fainting spells.
• Mitral Valve Disease: When the thickened heart muscle obstructs blood flow, it can affect the mitral valve, located between the left heart chambers. The mitral valve may not close properly, leading to blood leaking backward into the left atrium. This condition, called mitral regurgitation, can worsen HCM symptoms.
• Dilated Cardiomyopathy: In a small percentage of HCM patients, the thickened heart muscle may weaken and lose its pumping strength over time. This can lead to dilated cardiomyopathy, where the heart chambers enlarge, particularly the left ventricle, and the heart pumps less forcefully.
• Heart Failure: Over time, the thickened heart muscle can become excessively stiff, hindering the heart’s ability to fill with blood. This can ultimately result in heart failure, where the heart cannot pump enough blood to meet the body’s needs.
• Fainting (Syncope): Irregular heartbeats or blocked blood flow can sometimes cause fainting. Unexplained fainting, especially in young individuals or if it’s a recent occurrence, can be a warning sign for sudden cardiac death.
• Sudden Cardiac Death: Although rare, hypertrophic cardiomyopathy can cause sudden cardiac death at any age. Tragically, sudden cardiac death may be the first indication of HCM in individuals who were previously unaware of their condition. This is a concern, particularly in young, seemingly healthy people, including athletes.

Prevention and Early Detection of HCM

Currently, there is no known way to prevent hypertrophic cardiomyopathy, as it is primarily a genetic condition. However, early detection is crucial for managing HCM, guiding treatment strategies, and preventing potential complications.

Given the genetic nature of HCM, family screening is essential. If you have a first-degree relative (parent, sibling, or child) with HCM, discuss genetic screening with your healthcare provider to determine if it is appropriate for you. However, it’s important to note that genetic testing may not detect all cases of HCM, and insurance coverage for genetic testing can vary.

If genetic testing is not performed or if the results are inconclusive, regular echocardiogram screenings are recommended, particularly for individuals with a family history of HCM. Echocardiograms use sound waves to create images of the heart, allowing for the detection of heart muscle thickening.

Echocardiogram Screening Recommendations for those with a family history of HCM:

• Initial echocardiogram screening around age 12.
• Repeat echocardiograms every 1 to 3 years throughout adolescence (ages 18-21).
• Subsequent screenings every five years throughout adulthood.

The frequency of echocardiogram screenings may be adjusted based on individual health status and the healthcare provider’s recommendations.

By Mayo Clinic Staff

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1. Maron MS. Hypertrophic cardiomyopathy: Clinical manifestations, diagnosis, and evaluation. https://www.uptodate.com/contents/search. Accessed Dec. 9, 2021.
2. Hypertrophic cardiomyopathy (HCM). American Heart Association. https://www.heart.org/en/health-topics/cardiomyopathy/what-is-cardiomyopathy-in-adults/hypertrophic-cardiomyopathy. Accessed Dec. 9, 2021.
3. AskMayoExpert. Hypertrophic cardiomyopathy (adult). Mayo Clinic; 2022.
4. Hypertrophic cardiomyopathy (HCM). American College of Cardiology. https://www.cardiosmart.org/topics/hypertrophic-cardiomyopathy. Accessed Dec. 9, 2021.
5. Thomas R. Ami. AllScripts EPSi. Mayo Clinic. Accessed Dec. 6, 2023.
6. Onmen SR, et al. 2020 AHA/ACC guideline for the diagnosis and treatment of patients with hypertrophic cardiomyopathy: Executive summary. Circulation. 2020; doi: 10.1161/CIR.0000000000000938.
7. Cirino AL, et al. Hypertrophic cardiomyopathy overview. GeneReviews. 2021; https://pubmed.ncbi.nlm.nih.gov/. Accessed Dec. 9, 2021.
8. Mankad R (expert opinion). Mayo Clinic. Nov. 15, 2023.
9. Dearani JA, et al. Surgery insight: Septal myectomy for obstructive hypertrophic cardiomyopathy — The Mayo Clinic experience. Nature Clinical Practice Cardiovascular Medicine. 2007; doi:10.1038/ncpcardio0965.
10. Kirklin JW, et al. Surgical relief of diffuse subvalvular aortic stenosis. Circulation. 1961; doi:10.1161/01.cir.24.4.739.
11. Maron BJ, et al. Diagnosis and evaluation of hypertrophic cardiomyopathy: JACC state-of-the-art review. Journal of the American College of Cardiology. 2022; doi:10.1016/j.jacc.2021.12.002.
12. Lloyd-Jones DM, et al. Life’s essential 8: Updating and enhancing the American Heart Association’s construct of cardiovascular health: A presidential advisory from the American Heart Association. Circulation. 2022; doi:10.1161/CIR.0000000000001078.

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