Hypertrophic Cardiomyopathy: Symptoms, Diagnosis & Treatment

What Is Hypertrophic Cardiomyopathy?

Hypertrophic cardiomyopathy (HCM) is a genetic disease that causes the heart muscle to become abnormally thickened, making it harder for the heart to pump blood effectively. It affects approximately 1 in 500 people worldwide and is the most common inherited heart condition, often running in families with a 50% inheritance risk.

Hypertrophic cardiomyopathy is a condition where the walls of the heart, particularly the left ventricle, become thicker than normal. This thickening occurs without an obvious cause such as high blood pressure or valve disease. The medical term "hypertrophic" means abnormally enlarged or thickened, while "cardiomyopathy" refers to a disease of the heart muscle itself.

The condition can affect the heart's function in several ways. When the heart muscle is abnormally thick, it becomes stiffer and less able to relax properly between beats. This can impair the heart's ability to fill with blood efficiently. In some cases, the thickened muscle can obstruct the flow of blood out of the heart, a condition known as hypertrophic obstructive cardiomyopathy (HOCM). The abnormal muscle tissue can also disrupt the heart's electrical signals, potentially causing irregular heartbeats.

Despite these potential problems, HCM varies enormously in its effects. Some people never experience any symptoms and discover they have the condition only through routine screening or when a family member is diagnosed. Others may develop significant symptoms that affect their daily activities. Understanding this spectrum is essential for both patients and their families, as it helps set realistic expectations about living with the condition.

Types of Hypertrophic Cardiomyopathy

HCM is broadly classified into two main types based on whether there is obstruction to blood flow leaving the heart. Obstructive HCM (HOCM) occurs when the thickened heart muscle partially blocks the outflow of blood from the left ventricle. This obstruction affects approximately two-thirds of HCM patients and can worsen symptoms. Non-obstructive HCM involves thickening of the heart muscle without significant obstruction to blood flow. While symptoms may still occur due to the stiff heart muscle, they are often less severe.

The location and pattern of thickening can also vary. In most cases, the interventricular septum (the wall between the two main pumping chambers) is most affected, a pattern called asymmetric septal hypertrophy. However, the thickening can occur in other parts of the heart, including the apex (tip) of the heart, a variant known as apical HCM that is particularly common in Asian populations.

What Are the Symptoms of Hypertrophic Cardiomyopathy?

The main symptoms of HCM include shortness of breath (especially during exertion), chest pain or tightness, heart palpitations, dizziness, and fainting (syncope). Many people with HCM have no symptoms at all. Symptoms often worsen during physical activity, after eating, or when dehydrated.

Hypertrophic cardiomyopathy presents a wide spectrum of symptoms, ranging from completely asymptomatic to severely limiting. The most common symptom is breathlessness during physical activity, which occurs because the stiff, thickened heart cannot fill efficiently and struggles to meet the body's increased oxygen demands during exercise. This symptom may develop gradually over years or remain stable for long periods.

Chest pain in HCM differs from that of a heart attack. Rather than being caused by blocked coronary arteries, chest discomfort in HCM typically results from the thickened muscle requiring more oxygen than the coronary arteries can supply, or from increased pressure within the heart. Patients often describe it as a pressure or squeezing sensation, frequently brought on by exertion and relieved by rest.

Palpitations are a frequent complaint and may represent various underlying heart rhythm disturbances. These can range from simple premature heartbeats, which are usually benign, to more serious arrhythmias like atrial fibrillation or ventricular tachycardia. Some patients describe their heart as racing, pounding, or fluttering in the chest. While often alarming, most palpitations in HCM are not immediately dangerous, though they warrant medical evaluation.

Fainting and Dizziness

Syncope (fainting) and presyncope (near-fainting or severe dizziness) are particularly important symptoms in HCM because they may indicate an increased risk of dangerous heart rhythms. Fainting can occur for several reasons: obstruction of blood flow from the heart that worsens during exertion, abnormal heart rhythms, or inappropriate drops in blood pressure. Any unexplained fainting episode in someone with HCM requires prompt medical evaluation to assess the risk of sudden cardiac death and determine whether preventive treatment is needed.

Some patients experience symptoms primarily after meals or when dehydrated. After eating a large meal, blood is redirected to the digestive system, which can worsen obstruction in those with HOCM. Similarly, dehydration reduces the amount of blood returning to the heart, which can worsen symptoms, particularly in patients with obstructive disease.

Symptoms in Children and Young Adults

In children and adolescents, HCM may first present during growth spurts when the heart muscle thickening becomes more pronounced. Young people may report reduced exercise tolerance compared to their peers, or they may unconsciously limit their activity to avoid symptoms. School physical examinations or sports physicals sometimes reveal heart murmurs that lead to the diagnosis. Unfortunately, in rare cases, sudden cardiac arrest during athletic activity may be the first indication of undiagnosed HCM.

• Shortness of breath: Especially during exercise or when lying flat
• Chest pain: Pressure or tightness, often with exertion
• Palpitations: Racing, pounding, or irregular heartbeat
• Fainting (syncope): May indicate serious arrhythmia risk
• Dizziness: Especially with standing or exertion
• Fatigue: Reduced energy and exercise tolerance

When Should You See a Doctor for HCM Symptoms?

Seek emergency care immediately if you experience severe chest pain, prolonged palpitations, fainting, or difficulty breathing. Schedule a routine appointment if you notice gradual worsening of symptoms, increased breathlessness during normal activities, or new symptoms such as ankle swelling. Family members of HCM patients should also be evaluated.

Knowing when to seek medical care is crucial for anyone with HCM or symptoms that might suggest the condition. Emergency evaluation is needed for any sudden, severe symptoms. Chest pain that is intense, prolonged, or associated with shortness of breath, sweating, or light-headedness requires immediate attention. Similarly, fainting episodes, especially those occurring during or shortly after exercise, demand urgent assessment because they may indicate dangerous heart rhythms.

Sustained palpitations lasting more than a few minutes, particularly if accompanied by chest discomfort, shortness of breath, or light-headedness, also warrant emergency evaluation. While most palpitations in HCM are not immediately life-threatening, some may represent arrhythmias that need urgent treatment. When in doubt, it is always safer to seek evaluation.

Non-emergency but important situations include gradual worsening of existing symptoms, such as increasing breathlessness during activities that were previously comfortable. New symptoms like ankle swelling may indicate the heart is struggling to maintain adequate circulation and should prompt medical review. Changes in heart rhythm patterns, even if brief, are worth discussing with your cardiologist.

First-degree relatives of anyone diagnosed with HCM should undergo screening, even if they feel completely well. This typically includes an electrocardiogram and echocardiogram, and in some cases genetic testing. Because HCM can develop at any age, periodic rescreening is recommended for those who initially test negative, particularly through adolescence and young adulthood when the condition most commonly manifests.

What Causes Hypertrophic Cardiomyopathy?

HCM is primarily caused by genetic mutations that affect proteins in the heart muscle cells responsible for contraction. Over 1,500 different mutations have been identified, most commonly in genes encoding sarcomeric proteins. The condition follows autosomal dominant inheritance, meaning each child of an affected parent has a 50% chance of inheriting the mutation.

Hypertrophic cardiomyopathy is fundamentally a genetic disease. In approximately 60% of cases, a specific gene mutation can be identified through genetic testing. The remaining cases likely also have a genetic basis, but the responsible mutation may not yet be identified by current testing methods or may result from complex interactions between multiple genes.

The most commonly affected genes encode proteins that make up the sarcomere, the basic contractile unit of heart muscle cells. The sarcomere is responsible for the heart's ability to contract and relax with each beat. When one of these proteins is abnormal due to a genetic mutation, the heart muscle cells do not function properly, leading over time to the characteristic thickening of the heart wall.

The two most commonly affected genes are MYH7 (encoding beta-myosin heavy chain) and MYBPC3 (encoding myosin-binding protein C), which together account for approximately 70% of cases where a mutation is found. Other sarcomeric genes that can be affected include those encoding troponin T, troponin I, alpha-tropomyosin, and actin. Each of these proteins plays a critical role in heart muscle contraction.

Inheritance Pattern

HCM follows an autosomal dominant inheritance pattern. This means that only one copy of the abnormal gene is needed to potentially cause the disease. If a parent carries an HCM-causing mutation, each child has a 50% chance of inheriting that mutation. This applies equally to both sons and daughters, as the condition is not linked to sex chromosomes.

However, inheriting the mutation does not guarantee developing symptoms or even visible heart thickening. This is known as variable penetrance and expressivity. Some people with HCM mutations develop severe disease at a young age, while others may have only mild thickening that never causes symptoms. Researchers are still working to understand why the same mutation can have such different effects in different family members.

In approximately 10-15% of cases, HCM appears without any family history. This may represent a new (de novo) mutation occurring for the first time in that individual, or it may indicate unknown family history, possibly due to relatives who had undiagnosed or asymptomatic disease.

Non-Genetic Factors

While HCM is genetically determined, several factors can influence how the disease manifests. Physical activity, particularly during childhood and adolescence when the heart is growing, may affect the degree of thickening that develops. High blood pressure can worsen hypertrophy in those predisposed to HCM. Some medications and illicit substances, particularly stimulants, can unmask or worsen symptoms in those with underlying HCM.

How Is Hypertrophic Cardiomyopathy Diagnosed?

HCM is diagnosed primarily through echocardiography (heart ultrasound), which shows the characteristic thickening of the heart muscle (typically 15mm or more in adults). Additional tests include ECG, cardiac MRI, exercise stress testing, Holter monitoring, and genetic testing. Family screening is essential for first-degree relatives.

The diagnostic process for hypertrophic cardiomyopathy typically begins when someone presents with suspicious symptoms, when a heart murmur is detected during examination, when ECG abnormalities are found, or when a family member is diagnosed with the condition. A careful medical history, including detailed family history, is the first step in evaluation.

Physical examination may reveal a heart murmur, particularly in those with obstructive HCM. The murmur is caused by turbulent blood flow through the narrowed outflow tract or by associated mitral valve leakage. The murmur typically increases with maneuvers that reduce blood volume in the heart (such as standing up or straining) and decreases with maneuvers that increase heart filling (such as squatting).

Key Diagnostic Tests

The echocardiogram (heart ultrasound) is the primary diagnostic test for HCM. It provides detailed images of the heart's structure and function without radiation exposure. The echocardiogram can measure wall thickness (15mm or greater in adults is diagnostic in the absence of other causes), assess for obstruction of blood flow, evaluate the function of heart valves, and monitor how well the heart is filling and pumping blood. In athletic individuals, distinguishing HCM from normal athletic heart enlargement can be challenging and may require additional testing.

The electrocardiogram (ECG) records the heart's electrical activity and is abnormal in approximately 90% of HCM patients. Common findings include signs of left ventricular hypertrophy, abnormal Q waves, and T wave inversions. However, ECG abnormalities are not specific to HCM and can occur in other conditions. Conversely, a normal ECG does not completely exclude HCM, particularly in young patients or those in early stages of the disease.

Cardiac MRI provides the most detailed images of the heart and is increasingly used in HCM evaluation. It can identify areas of thickening that may be missed by echocardiography, particularly at the apex. Importantly, cardiac MRI can detect myocardial fibrosis using a technique called late gadolinium enhancement. The extent of fibrosis has prognostic significance, as more fibrosis is associated with higher risk of dangerous heart rhythms and heart failure.

Genetic Testing

Genetic testing plays an increasingly important role in HCM diagnosis and family management. When a mutation is identified in an affected individual (the proband), family members can undergo targeted genetic testing to determine whether they carry the same mutation. Those who test negative can be reassured that they do not need ongoing cardiac surveillance for HCM, while those who test positive require regular monitoring even if their hearts appear normal initially.

Genetic testing is performed through a blood test and typically analyzes multiple genes associated with HCM. Results usually take several weeks. It's important to understand that genetic testing doesn't find a mutation in all cases of clinically diagnosed HCM, and a negative result doesn't exclude the diagnosis. Genetic counseling should be offered before and after testing to help patients and families understand the implications of results.

What Treatments Are Available for Hypertrophic Cardiomyopathy?

Treatment options for HCM include medications (beta-blockers, calcium channel blockers, mavacamten), procedures to reduce obstruction (septal myectomy surgery or alcohol septal ablation), and implantable cardioverter-defibrillators (ICDs) for those at high risk of sudden death. Treatment is individualized based on symptoms, obstruction, and risk factors.

The treatment approach for hypertrophic cardiomyopathy is highly individualized and depends on several factors: whether symptoms are present, whether there is obstruction to blood flow, the risk of sudden cardiac death, and the development of complications such as atrial fibrillation or heart failure. Many patients with mild disease require only regular monitoring without active treatment.

For those with symptoms, treatment aims to improve quality of life by reducing symptoms such as breathlessness, chest pain, and palpitations. For those at elevated risk of sudden cardiac death, treatment focuses on prevention of this devastating outcome. Understanding the goals of treatment helps patients make informed decisions about their care.

Medication Therapy

Beta-blockers are typically the first-line medication for symptomatic HCM. By slowing the heart rate and reducing the force of contraction, beta-blockers give the heart more time to fill between beats and can reduce obstruction in those with HOCM. Common beta-blockers used include metoprolol, propranolol, and bisoprolol. Side effects can include fatigue, cold extremities, and in some cases depression or sexual dysfunction.

Calcium channel blockers, particularly verapamil and diltiazem, are an alternative for patients who cannot tolerate beta-blockers or who need additional symptom control. These medications work by relaxing the heart muscle and slowing the heart rate. They should be used cautiously in patients with severe obstruction, as they can occasionally worsen symptoms.

Mavacamten represents a breakthrough in HCM treatment. Approved in 2022, it is the first medication specifically designed to target the underlying abnormality in HCM. It works by reducing the excessive contractility of the heart muscle, thereby decreasing obstruction and improving symptoms. Clinical trials showed significant improvement in exercise capacity and symptoms. The medication requires regular monitoring of heart function, as excessive effect can temporarily reduce the heart's pumping ability.

Disopyramide is an antiarrhythmic medication that has been used for decades to reduce obstruction in HOCM. It has a negative inotropic effect, meaning it reduces the force of heart contraction, which can decrease the obstruction. It is typically used in combination with a beta-blocker and requires monitoring for side effects including dry mouth, urinary retention, and heart rhythm effects.

Procedures for Obstructive HCM

When medications fail to adequately control symptoms in obstructive HCM, procedures to physically reduce the obstruction may be considered. Both surgical and catheter-based options are available.

Septal myectomy is open-heart surgery in which the surgeon removes a portion of the thickened septum causing the obstruction. This procedure has been performed for over 50 years and has excellent long-term outcomes when performed at experienced centers. Most patients experience significant symptom improvement, and the procedure has a low mortality rate (less than 1% at expert centers). Septal myectomy is generally considered the gold standard treatment for drug-refractory obstructive HCM.

Alcohol septal ablation is a catheter-based alternative that does not require open-heart surgery. During this procedure, a small amount of alcohol is injected into a coronary artery branch that supplies the obstructing portion of the septum, causing a controlled, localized injury that shrinks the tissue over time. While less invasive than surgery, it carries a higher risk of requiring a permanent pacemaker and may be less effective in some patients. It is typically considered for older patients or those with significant surgical risk.

Implantable Cardioverter-Defibrillator (ICD)

The implantable cardioverter-defibrillator is a device that can detect and terminate dangerous heart rhythms that could otherwise cause sudden cardiac death. It is placed under the skin of the chest and connected to the heart by one or more leads. When a life-threatening arrhythmia is detected, the ICD delivers an electrical shock to restore normal rhythm.

Deciding who should receive an ICD is one of the most important aspects of HCM management. Current guidelines recommend ICD implantation for patients who have already survived a cardiac arrest or sustained dangerous arrhythmia (secondary prevention). For primary prevention, risk calculators incorporating multiple factors (family history of sudden death, unexplained syncope, severe hypertrophy, abnormal blood pressure response to exercise, non-sustained ventricular tachycardia, and extensive fibrosis on MRI) help estimate the 5-year risk of sudden death to guide decision-making.

How Does Genetic Testing Work for HCM?

Genetic testing identifies mutations in genes responsible for HCM, most commonly MYH7 and MYBPC3. When a mutation is found, family members can undergo targeted "cascade" testing. Those who test positive need regular cardiac monitoring even if currently healthy, while those testing negative can be reassured they won't develop HCM from that family mutation.

Genetic testing has transformed the management of HCM families. The process typically begins with comprehensive genetic testing of the person clinically diagnosed with HCM. A blood sample is sent to a specialized laboratory where DNA is extracted and analyzed for mutations in genes known to cause HCM. Most testing panels examine 10-20 or more genes, with results typically available in 4-8 weeks.

Approximately 30-60% of HCM patients will have an identifiable genetic mutation. When a mutation is found, this information becomes extremely valuable for family screening. First-degree relatives (parents, siblings, and children) can then undergo "cascade" genetic testing, a simpler and less expensive test that specifically looks for the known family mutation.

The implications of genetic test results require careful interpretation with genetic counseling support. A positive result in a clinically affected individual confirms the genetic nature of their disease and enables family screening. A positive result in a clinically unaffected family member indicates they carry the mutation and should undergo regular cardiac imaging to monitor for disease development, as HCM can appear at any age.

When No Mutation Is Found

When genetic testing doesn't identify a mutation (a negative or inconclusive result), this does not mean the disease isn't genetic. Current testing technology doesn't detect all possible mutations, and some HCM cases may be caused by genes not yet included in testing panels or by complex genetic factors. In these families, all first-degree relatives should still undergo clinical screening with ECG and echocardiography, with periodic rescreening recommended.

Implications for Family Planning

Knowing about HCM and its genetic basis allows families to make informed decisions about family planning. Options include natural conception with awareness of the 50% inheritance risk, preimplantation genetic testing during IVF to select embryos without the mutation, or prenatal testing during pregnancy. These decisions are deeply personal, and genetic counselors can help families explore their options without judgment.

What Lifestyle Changes Help Manage HCM?

People with HCM should avoid competitive sports and high-intensity exercise but can usually engage in moderate recreational activities. Staying well-hydrated, avoiding excessive alcohol, taking medications as prescribed, and attending regular cardiac follow-up are essential. Always inform healthcare providers about your HCM diagnosis before any procedure or new medication.

Living well with HCM involves understanding how the condition affects daily activities and making appropriate adjustments. The goal is to minimize risk while maintaining quality of life. For many patients, lifestyle modifications are sufficient to manage the condition effectively, particularly when combined with regular medical surveillance.

Exercise and Physical Activity

Exercise recommendations for HCM have evolved significantly in recent years. While competitive sports and high-intensity exercise remain inadvisable for most patients due to the association between HCM and sudden death during intense exertion, recent guidelines have become more permissive regarding recreational physical activity.

Moderate-intensity recreational exercise is generally considered safe and is encouraged for cardiovascular and overall health. This might include brisk walking, cycling at a comfortable pace, swimming, golf, or doubles tennis. The key is avoiding activities that require sudden bursts of maximum effort or that significantly increase heart rate and blood pressure. Exercise should be stopped if symptoms such as chest pain, severe breathlessness, dizziness, or palpitations occur.

For athletes diagnosed with HCM, the recommendation to retire from competitive sports can be devastating. However, understanding that this advice is based on preventing potentially fatal events during competition helps most patients accept this limitation. Some athletes with low-risk features may be able to continue certain activities after detailed risk assessment and shared decision-making with their cardiologist, though this remains controversial.

Hydration and Alcohol

Maintaining adequate hydration is particularly important for people with obstructive HCM. When blood volume is low (from dehydration, heat exposure, or certain medications), less blood returns to the heart, which can worsen obstruction and symptoms. Patients should drink plenty of fluids, particularly in hot weather or during illness that causes fluid loss.

Excessive alcohol consumption should be avoided for several reasons. Alcohol can trigger atrial fibrillation, a common complication of HCM that increases stroke risk. Long-term heavy drinking can also directly damage the heart muscle, potentially worsening HCM. Moderate alcohol consumption (no more than one drink daily for women or two for men) is generally acceptable for most patients, but individual recommendations should be discussed with your cardiologist.

Medical Precautions

Always inform any healthcare provider treating you about your HCM diagnosis. This is important because certain medications can worsen symptoms or be dangerous in HCM. These include vasodilators (which can worsen obstruction), digoxin in obstructive disease, and some decongestants. Before any surgical or dental procedure, discuss whether antibiotic prophylaxis for endocarditis prevention is recommended, as guidelines vary based on specific circumstances.

Is Pregnancy Safe with Hypertrophic Cardiomyopathy?

Most women with HCM can safely have children, though pregnancy requires careful monitoring by a specialized team. Risks are higher for women who have symptoms before pregnancy, have severe obstruction, or have heart failure. Planning pregnancy in advance and ensuring care at a center experienced with HCM in pregnancy is recommended.

Pregnancy is possible for most women with HCM, though it requires more monitoring than a typical pregnancy. The cardiovascular changes of pregnancy, including increased blood volume and heart rate, can affect symptoms but are usually well tolerated. Studies show that maternal mortality is low and most pregnancies have good outcomes when properly managed.

Women with no symptoms or mild symptoms before pregnancy generally do best. Higher risk factors include significant symptoms prior to pregnancy, severe left ventricular outflow obstruction, prior arrhythmias (particularly atrial fibrillation), and reduced heart function. Women with these features should discuss their individual risk with a cardiologist before becoming pregnant.

Some HCM medications are not safe during pregnancy. Beta-blockers can be used but require monitoring of the baby's growth. Mavacamten and disopyramide should be stopped before conception. Pregnancy planning allows time to adjust medications and optimize the mother's condition before pregnancy.

Delivery planning should involve a multidisciplinary team including cardiologists, obstetricians experienced in high-risk pregnancy, and anesthesiologists. Vaginal delivery is usually possible for women with well-controlled HCM. Cesarean section is typically reserved for obstetric indications rather than HCM itself, though individual circumstances vary.

Hereditary Considerations

Parents with HCM naturally wonder about the risk to their children. If a causative mutation has been identified, there is a 50% chance each child will inherit it. However, inheriting the mutation doesn't guarantee developing symptoms or even visible disease. Prenatal testing and preimplantation genetic testing are available for families who wish to avoid passing on the mutation. Genetic counseling can help families understand their options and make informed decisions.

What Is the Long-Term Outlook for People with HCM?

Most people with HCM have a normal or near-normal life expectancy with modern management. The annual mortality rate is less than 1% with appropriate monitoring and treatment. Risk stratification helps identify those who may benefit from preventive measures like ICDs. Quality of life is good for most patients with proper management.

The prognosis for hypertrophic cardiomyopathy has improved dramatically over the past few decades due to better understanding of the condition, improved risk stratification, and availability of effective treatments including ICDs for those at highest risk of sudden death. While HCM was once considered a highly dangerous condition, we now know that most affected individuals can lead full, active lives.

Annual mortality rates for HCM patients are now estimated at 0.5-1% when patients receive appropriate care at experienced centers. This is far better than older estimates, which were skewed by inclusion of the most severely affected patients. With modern management, life expectancy for most HCM patients approaches that of the general population.

Several factors influence individual prognosis. Those with no symptoms and no high-risk features have excellent outcomes. Progressive heart failure occurs in a minority of patients over time, though treatments for heart failure can be very effective. Atrial fibrillation is common and increases stroke risk but can be managed with blood thinners and rhythm control strategies. Sudden cardiac death risk can be assessed and mitigated with ICDs when appropriate.

Complications and Their Management

Heart failure can develop in some HCM patients, either from the stiff heart's impaired filling (diastolic heart failure) or from eventual weakening of the heart muscle (systolic heart failure). Standard heart failure medications are effective, and in severe cases, heart transplantation can be considered.

Atrial fibrillation affects 20-25% of HCM patients and significantly increases stroke risk. Anticoagulation (blood thinning medication) is almost always recommended for HCM patients who develop atrial fibrillation, regardless of the typical risk scores used in other populations. Rate and rhythm control strategies help manage symptoms.

Sudden cardiac death remains the most feared complication but can be prevented in most cases through appropriate risk assessment and ICD implantation when indicated. The development of refined risk calculators has improved our ability to identify those who benefit most from preventive ICDs.