Hypertrophic Cardiomyopathy

Overview

Hypertrophic cardiomyopathy is an inherited heart muscle disease in which the heart muscle becomes abnormally thick. This thickening most commonly affects the left ventricle and the wall separating the two ventricles. As the muscle thickens, it can obstruct the flow of blood leaving the heart. The stiffened muscle also has difficulty relaxing and filling properly between beats.

Hypertrophic cardiomyopathy is one of the most common causes of sudden cardiac arrest in young and apparently healthy individuals, including competitive athletes. For this reason, it requires careful evaluation and ongoing management, particularly in younger people. Many individuals with the condition, however, live for decades without significant symptoms. The disease is often discovered incidentally during a routine examination or when a family member is diagnosed.

Because hypertrophic cardiomyopathy is an inherited condition, first-degree relatives of an affected person are at meaningful risk and should be evaluated. With early diagnosis and appropriate treatment, the risk of serious complications can be significantly reduced and most people can lead a normal or near-normal life.

Symptoms

A significant proportion of people with hypertrophic cardiomyopathy have no symptoms for much of their lives. The condition may first come to attention through family screening or an incidentally found heart abnormality on a test done for another reason. When symptoms do occur, they are most often related to physical exertion.

• Shortness of breath. This is the most common symptom. Because the stiffened heart muscle cannot relax and fill normally between beats, fluid can back up into the lungs. Breathlessness typically begins during exercise but may occur at rest as the condition progresses.
• Chest pain. This often occurs during or immediately after exercise. The thickened heart muscle has a higher oxygen demand than coronary arteries can always meet during physical activity, producing a pressure-like or squeezing discomfort in the chest.
• Palpitations or irregular heartbeat. The abnormally thickened and stiffened heart muscle is prone to rhythm disturbances. Atrial fibrillation and ventricular arrhythmias are both more common in hypertrophic cardiomyopathy. The heart may feel as though it is racing, pounding, or beating irregularly.
• Dizziness or lightheadedness. Insufficient blood reaching the brain during or after exercise can produce a feeling of unsteadiness or dizziness.
• Fainting. Loss of consciousness during or immediately after exercise is a particularly important warning sign in hypertrophic cardiomyopathy. It may reflect a serious rhythm disturbance or a significant obstruction to blood leaving the heart. This symptom should always be taken seriously and evaluated without delay.
• Fatigue. Reduced pumping efficiency can produce a persistent sense of exhaustion. Exercise capacity may be noticeably lower than expected for the person's age and fitness level.

When to Seek Medical Care

See a doctor if you notice any of the following.

• Shortness of breath or chest pain during or after exercise
• Palpitations or a sensation of irregular heartbeat
• Unexplained fatigue or exercise capacity that seems lower than it should be
• Dizziness or lightheadedness

Call emergency services immediately if you experience any of the following.

• Fainting or nearly fainting, especially during or after exercise
• Sudden, severe chest pain
• A very rapid or markedly irregular heartbeat
• Sudden, severe shortness of breath

Causes

Hypertrophic cardiomyopathy is caused almost exclusively by inherited changes in genes that code for the structural proteins of the heart muscle. These gene changes cause the heart muscle fibers to grow in a disorganized, abnormally thickened pattern. The condition follows an autosomal dominant inheritance pattern, meaning that a person who carries the gene change has approximately a 50 percent chance of passing it on to each of their children.

Several different gene changes have been identified. The most frequently affected genes code for proteins involved in the heart muscle's contraction, such as myosin and troponin. Even among family members who carry the same gene change, the degree of muscle thickening and the severity of the condition can vary considerably. A positive genetic test result therefore does not predict exactly how the disease will present in any individual person. Regular cardiology monitoring is essential for anyone found to carry a relevant gene change.

Risk Factors

Because hypertrophic cardiomyopathy is almost always genetic in origin, the most important risk factor is a family history of the condition.

• Family history of hypertrophic cardiomyopathy. Having a parent, sibling, or child with the diagnosis carries approximately a 50 percent chance of inheriting the gene change. Screening of first-degree relatives is strongly recommended.
• A positive genetic test result. Someone found to carry a relevant gene change should receive regular cardiac monitoring even if the heart muscle appears normal at first, since the condition can manifest later in life.
• Young male sex. While hypertrophic cardiomyopathy occurs in both sexes, the risk of sudden cardiac arrest is higher in men and particularly in young, physically active individuals.
• High-intensity competitive sport. In people who do not yet know they have the condition, vigorous competitive exercise increases the risk of sudden cardiac arrest. This is why cardiac screening in young athletes is an important public health consideration.

Diagnosis

The diagnosis of hypertrophic cardiomyopathy is made through clinical assessment, imaging, and testing. In many patients, the diagnosis is first suspected during family screening or when an abnormal heart finding is noted on a test done for an unrelated reason. The diagnostic process aims not only to confirm the presence of the condition but also to assess whether blood flow is obstructed, whether dangerous rhythm disturbances are present, and what the individual's risk of sudden cardiac arrest is.

• Medical history and physical examination. The doctor asks in detail about symptoms, when they began, and what triggers them. A family history of hypertrophic cardiomyopathy, unexplained sudden cardiac death, or heart failure at a young age is specifically important and should always be mentioned. On physical examination, a characteristic heart murmur may be heard. This murmur results from turbulence as blood passes through the narrowed outflow tract. A feature that is quite specific to hypertrophic cardiomyopathy is that this murmur becomes louder when the person stands up or performs a Valsalva maneuver, both of which reduce the amount of blood in the heart and worsen the obstruction.
• Echocardiogram (heart ultrasound). This is the cornerstone of diagnosis. It measures left ventricular wall thickness in millimeters. A wall thickness of 15 millimeters or more in an adult is considered a strong diagnostic criterion. The echocardiogram also shows whether the outflow tract is obstructed and, if so, by how much. This obstruction may be absent at rest and only appear during exertion or with a Valsalva maneuver, so measurement under provoked conditions may be needed. The mitral valve is also assessed. In hypertrophic cardiomyopathy, the mitral valve can move forward abnormally during contraction, further narrowing the outflow tract. The filling pattern and size of the left atrium are also evaluated.
• Electrocardiogram (ECG). The ECG is abnormal in the great majority of people with hypertrophic cardiomyopathy and is often what first raises clinical suspicion. Common findings include increased voltage reflecting left ventricular thickening, deep T-wave inversions, and Q-wave abnormalities. While an abnormal ECG strongly supports the diagnosis, a normal ECG does not exclude it, and imaging is always required.
• Holter monitor. A portable ECG device worn for 24 hours or longer that continuously records the heart rhythm during normal activity. Atrial fibrillation is a common and clinically important rhythm problem in hypertrophic cardiomyopathy. Brief runs of ventricular tachycardia, which can precede a life-threatening event, may also be captured. These findings are important for assessing the risk of sudden cardiac arrest and for guiding treatment decisions, including whether an ICD is indicated.
• Cardiac MRI. Used alongside echocardiography to provide information that cannot be obtained from ultrasound alone. It precisely maps the location and extent of thickening across all regions of the heart. Crucially, using a technique called late gadolinium enhancement, it can identify areas of fibrosis or scarring within the heart muscle. The presence and extent of fibrosis is directly associated with the risk of sudden cardiac arrest and is one of the most important factors informing the ICD decision. Cardiac MRI is particularly valuable when echocardiographic images are suboptimal and when surgical planning is being considered.
• Exercise stress test. Assesses the heart's response to physical exertion by monitoring the ECG, blood pressure, and heart rate during a treadmill or exercise bike test. A blood pressure that fails to rise or actually falls during exercise is an important warning sign and contributes to the overall risk assessment for sudden cardiac arrest. Exercise-induced rhythm disturbances can also be identified. The test additionally provides an objective measure of exercise capacity.
• Blood tests. Standard blood tests are not directly diagnostic of hypertrophic cardiomyopathy. However, BNP and NT-proBNP levels reflect the degree of pressure on the heart and can help assess severity. If atrial fibrillation is present, additional testing to evaluate clot risk is needed.
• Genetic testing and family screening. Genetic testing is recommended to support the diagnosis and, most importantly, to guide family screening. A blood or saliva sample is tested for gene changes associated with hypertrophic cardiomyopathy. A positive result confirms the genetic basis of the condition and identifies which relatives should be evaluated. If a gene change is found, first-degree relatives — parents, siblings, and children — should undergo echocardiography and cardiology evaluation. A negative genetic test does not rule out the condition if clinical findings are present; both results need to be interpreted together.
• Electrophysiology study. Not performed routinely. When Holter monitoring or other tests identify significant ventricular rhythm disturbances, this procedure may be used to map the electrical pathways of the heart in detail and identify the origin of the abnormal rhythm. Thin electrode catheters are placed through blood vessels into the heart for this purpose.

Treatment

Treatment of hypertrophic cardiomyopathy has two core goals. The first is to relieve symptoms and preserve quality of life. The second is to prevent serious complications, most importantly sudden cardiac arrest. The treatment approach is shaped by whether the outflow tract is obstructed, the severity of symptoms, and each individual's risk profile.

Medications

• Beta-blockers. These are the first medication tried in most patients. By slowing the heart rate, they allow more time for the heart to fill between beats. This improves both symptoms and, in many patients, the degree of outflow obstruction. They are started at a low dose and gradually increased.
• Verapamil. A calcium channel blocker that is considered when beta-blockers are not well tolerated or do not provide adequate symptom relief. It reduces the force of the heart muscle's contraction and slows the heart rate, improving filling and relieving symptoms. It is not used in combination with a beta-blocker.
• Disopyramide. An antiarrhythmic medication that directly reduces the strength of the heart muscle's contraction, which can meaningfully reduce outflow obstruction. It is used in combination with a beta-blocker or verapamil rather than alone, and is most often added when the obstruction persists despite initial treatment.
• Mavacamten. A newer targeted medication that acts at the molecular level by inhibiting myosin, the protein responsible for the heart muscle's contraction. By reducing the excessive force of contraction, it directly addresses the mechanism underlying the obstruction. Clinical trials have shown it significantly reduces outflow obstruction and improves both symptoms and exercise capacity. It may be considered in patients who do not respond adequately to older medications or in preparation for a decision about invasive treatment. Regular echocardiographic monitoring is required during use.
• Medications for rhythm disturbances. Atrial fibrillation is a common and important complication of hypertrophic cardiomyopathy. Medications to control heart rate or maintain normal rhythm may be required. Because atrial fibrillation substantially increases the risk of clot formation and stroke in hypertrophic cardiomyopathy, blood-thinning medication is typically required when atrial fibrillation is present.

Interventional Treatments

• Septal myectomy. This is an open-heart operation performed in patients with significant outflow obstruction whose symptoms have not been adequately controlled with medications. The surgeon removes a small amount of muscle from the thickened septal wall inside the heart, widening the outflow tract and substantially or completely eliminating the obstruction. In experienced centers, septal myectomy offers excellent and durable long-term results and is recognized worldwide as the gold standard treatment for obstructive hypertrophic cardiomyopathy. Most patients experience major or complete resolution of symptoms after the procedure.
• Alcohol septal ablation. A catheter-based alternative for patients who are not suitable candidates for surgery or who prefer a less invasive approach. A thin catheter is passed through a blood vessel in the groin to the heart. Through this catheter, a small amount of pure alcohol is carefully delivered into the small artery that supplies the thickened portion of the septal wall. The alcohol causes a controlled, localized area of the muscle to weaken, producing a small, targeted area of scarring. Over the following weeks to months, the outflow obstruction decreases. The procedure is less invasive than surgery and requires a shorter hospital stay. However, it carries a specific risk of causing heart block, which may require pacemaker implantation, and is not anatomically suitable for all patients. The choice between septal myectomy and alcohol septal ablation should be made by an experienced multidisciplinary team based on each patient's anatomy and clinical circumstances.

Preventing Sudden Cardiac Arrest

• Implantable cardioverter-defibrillator (ICD). This small device is implanted under the chest skin and connected to the heart by thin wires. It continuously monitors the heart rhythm and delivers an electrical shock to restore a normal rhythm if a life-threatening arrhythmia is detected. Several factors are associated with higher sudden cardiac arrest risk in hypertrophic cardiomyopathy. These include a prior cardiac arrest or sustained ventricular tachycardia, a family history of sudden cardiac death due to hypertrophic cardiomyopathy, very marked wall thickening, a blood pressure that fails to rise adequately during exercise, frequent non-sustained ventricular tachycardia on Holter monitoring, and extensive fibrosis on cardiac MRI. The ICD decision is made by weighing all of these factors together in the context of each individual patient. Once implanted, the device remains in place permanently and the battery is replaced as needed.

Exercise Restriction

High-intensity and competitive sport is generally not recommended in hypertrophic cardiomyopathy because vigorous exertion increases the risk of sudden cardiac arrest. This applies to all patients with the diagnosis, whether or not they currently have symptoms. The decision about which physical activities are safe for a specific individual must be made by a cardiologist familiar with the condition. Do not make this decision independently based on how you feel.

Complications

Without adequate treatment and monitoring, hypertrophic cardiomyopathy can lead to serious complications.

• Sudden cardiac arrest. This is the most feared complication. Hypertrophic cardiomyopathy is one of the most common causes of sudden cardiac arrest in young and otherwise healthy people. In some individuals, sudden cardiac arrest is the first manifestation of a condition that was previously unrecognized. This is why family screening is so critical.
• Atrial fibrillation. The abnormally thickened and stiffened heart muscle predisposes to rhythm disturbances. Atrial fibrillation causes palpitations and breathlessness, and substantially increases the risk of blood clot formation and stroke in people with hypertrophic cardiomyopathy. It requires its own specific management, including blood-thinning therapy.
• Heart failure. Many patients remain stable for decades, but a proportion do eventually develop heart failure. The stiffened muscle may become increasingly unable to fill adequately, or in rare cases the pumping function of the heart gradually declines.
• Stroke. Clots forming in the heart as a result of atrial fibrillation can travel to the brain and cause a stroke. This risk can be significantly reduced with appropriate blood-thinning treatment.
• Mitral valve regurgitation. In hypertrophic cardiomyopathy, the mitral valve operates in an abnormal position. This can cause blood to leak backward through the valve, worsening symptoms and increasing the workload on the heart.

Lifestyle

For most people, hypertrophic cardiomyopathy can be well managed, and a fulfilling and active life is entirely achievable. Some important considerations, however, directly affect both safety and long-term outcomes.

Exercise and Sport

Exercise in hypertrophic cardiomyopathy requires individualized guidance. High-intensity and competitive sport is generally not recommended because vigorous exercise can increase the risk of dangerous rhythm disturbances and sudden cardiac arrest. This recommendation applies to people with and without symptoms alike.

That said, complete inactivity is not the right approach. Light to moderate activities such as walking, yoga, and easy cycling are safe for most patients. The type and intensity of exercise that is appropriate for you specifically should be determined by your cardiologist. Do not assume that feeling well means any level of exercise is safe.

Avoiding Dehydration and Extreme Heat

In hypertrophic cardiomyopathy, particularly in those with outflow obstruction, dehydration can worsen the condition. A reduced blood volume makes it harder for the heart to fill adequately and can intensify the obstruction. During hot weather, physical activity, or illnesses involving vomiting or diarrhea, take care to maintain adequate fluid intake. Prolonged hot baths and saunas can also be problematic and are worth avoiding.

Medications

Some commonly used medications can worsen hypertrophic cardiomyopathy by dilating blood vessels or reducing blood volume, which intensifies the outflow obstruction. This includes some blood pressure medications and high-dose nitrate-containing preparations. Before starting or stopping any medication, always consult your cardiologist. Whenever you are being treated by another doctor for any reason, make sure they are aware of your hypertrophic cardiomyopathy diagnosis.

Family Screening

Because hypertrophic cardiomyopathy is an inherited condition, first-degree relatives — parents, siblings, and children — should undergo cardiac evaluation including echocardiography. Screening is ideally repeated every three to five years in adults, and more frequently in children and adolescents who are still growing. A single normal result does not end the need for monitoring, as the condition can appear later in life. Relatives who test positive for a relevant gene change require more regular surveillance.

Emotional Wellbeing

Receiving a diagnosis of cardiomyopathy, particularly at a young age, can carry a significant psychological burden for both the patient and their family. Having to give up competitive sport, having experienced a blackout, or learning about the risk of sudden death can contribute to anxiety and depression. Sharing these feelings openly and seeking professional support when needed is an important part of managing life with this condition.

Regular Follow-up

Hypertrophic cardiomyopathy requires ongoing monitoring. Echocardiography and ECG are used periodically to assess wall thickness, outflow obstruction, and heart rhythm. Holter monitoring is repeated when needed. A risk reassessment for sudden cardiac arrest is recommended at least annually. Contact your doctor promptly or seek emergency care if any of the following develop.

• Fainting or nearly fainting, especially during or after exercise
• New or worsening chest pain or shortness of breath
• Palpitations or a very rapid heartbeat
• Unexplained dizziness or lightheadedness

Preparing for Your Appointment

Coming prepared to an appointment for hypertrophic cardiomyopathy helps your doctor make a more accurate assessment and choose the most appropriate treatment for you.

What You Can Do

• Write down when symptoms began and in what situations they occur. Their relationship to exercise is particularly important.
• Mention any episodes of fainting or nearly fainting, especially during physical activity.
• Share any family history of hypertrophic cardiomyopathy, unexplained sudden cardiac death, or heart failure at a young age.
• List all medications, supplements, and herbal products you are currently taking.
• Describe your exercise habits and what type of physical activity you engage in.
• Write your questions down before the appointment.

Questions You May Wish to Ask Your Doctor

• Is there obstruction to blood leaving my heart and how significant is it?
• What is my risk of sudden cardiac arrest?
• Do I need an implantable defibrillator?
• Which medications are most appropriate for me?
• Could septal myectomy or alcohol septal ablation be an option for me?
• What type and intensity of exercise is safe for me?
• Should my family members be screened?
• Are there any medications I should avoid?
• How often do I need follow-up appointments?

Questions Your Doctor May Ask You

• When did symptoms begin and are they related to exercise?
• Have you ever fainted or nearly fainted?
• Is there a family history of hypertrophic cardiomyopathy or unexplained sudden cardiac death at a young age?
• What type of sport or physical activity do you do, and at what intensity?
• What medications are you currently taking?
• Have you ever experienced an abnormal heart rhythm?
• Are you planning a pregnancy?