Understanding How Common Hypertrophic Cardiomyopathy Is

Hypertrophic cardiomyopathy affects approximately 1 in 500 people in the United States, making it more common than many people realize.^[1] This translates to roughly 1 in 500 to 1 in 1,000 individuals globally having this condition.^[3] Despite these numbers, many people who have hypertrophic cardiomyopathy remain unaware of their condition because they may not experience any noticeable symptoms.^[4]

The condition represents the most common identifiable cause of sudden cardiac death in healthy people younger than 35 years of age, including well-trained athletes.^[3] This sobering fact highlights the importance of proper screening and diagnosis, particularly in young people who participate in competitive sports or those with a family history of heart problems.

While hypertrophic cardiomyopathy can develop at any age, most people with the condition receive a diagnosis around 40 years of age.^[4] Those who develop symptoms before age 40 often experience more symptoms and complications compared to those diagnosed later in life.^[5] The age at which family members develop this condition can vary significantly, even within the same biological family.

What Causes the Heart Muscle to Thicken

The root cause of hypertrophic cardiomyopathy lies in our genetic makeup. About 60% of patients with this condition have a known gene mutation affecting the sarcomere, which is the part of heart muscle cells responsible for contraction.^[3] These genes provide instructions for making proteins that form the contractile machinery of the heart, and when they don’t work properly, the heart muscle grows abnormally thick.

Gene changes cause about 3 in 5 cases of hypertrophic cardiomyopathy, and healthcare providers call this familial HCM.^[4] The genetic changes are to genes responsible for controlling heart muscle growth. Several hundred mutations in more than 27 genes have been associated with hypertrophic cardiomyopathy, which helps explain why the condition can look so different from one person to another.^[11]

When hypertrophic cardiomyopathy runs in families, it follows an autosomal dominant inheritance pattern.^[4] This means only one biological parent needs to have an altered gene to pass it on to their children. If a parent has the genetic change for hypertrophic cardiomyopathy, each child has a 50% chance of inheriting it.^[5] However, having the genetic change doesn’t guarantee that someone will develop symptoms or even noticeable heart thickening, as some people who carry the gene mutation never develop the disease.

Who Is at Higher Risk

The most significant risk factor for developing hypertrophic cardiomyopathy is having a family history of the condition. When someone in your family has been diagnosed with hypertrophic cardiomyopathy, that person can have genetic testing to look for the specific genetic changes that cause the condition.^[5] Once the genetic change is identified in one family member, other relatives can be tested for that same change.

Family members who should consider screening include parents, siblings, and children of someone diagnosed with hypertrophic cardiomyopathy. The age at which other family members develop the condition can vary within families, making it important to maintain regular monitoring even if tests initially come back normal.^[5]

A particularly important warning sign is a family history of sudden death, especially in people younger than age 40.^[5] If you have a family member who died suddenly before reaching middle age, it’s crucial to let your healthcare provider know, as you might need to be screened for hypertrophic cardiomyopathy. Family health history should also include information on relatives with heart failure, atrial fibrillation (an irregular heart rhythm), stroke, heart attack, heart transplant, or those who needed an implantable cardioverter-defibrillator or pacemaker.

Because the severity of hypertrophic cardiomyopathy can vary widely even within the same biological family, obtaining a detailed family history becomes crucial for risk stratification and determining appropriate monitoring schedules.^[3] This information helps doctors make informed decisions about how often to screen family members and what preventive measures might be necessary.

Recognizing the Symptoms

Many people with hypertrophic cardiomyopathy don’t realize they have it because they experience few, if any, symptoms.^[1] This makes the condition particularly challenging to identify without proper screening. However, when symptoms do occur, they can significantly affect daily life and require medical attention.

The most common symptoms include chest pain, especially during physical activity or exercise.^[1] This happens because the thickened heart muscle requires more energy and oxygen to work properly, particularly when you’re active.^[5] Some people describe feeling short of breath and fatigued, especially when they try to exercise or engage in physical activities that used to feel manageable.

Dizziness and fainting represent more concerning symptoms that should never be ignored. Fainting may occur especially during or just after exercise or other physical activity.^[1] Some people experience a sensation of fast, fluttering, or pounding heartbeats called palpitations, which can feel frightening even when they’re not immediately dangerous. Swelling, known as edema, may develop in the lower part of the body or in the neck veins.^[4]

Symptoms may worsen when a person becomes dehydrated, as this reduces the volume of blood in the vessels and can promote obstruction of blood flow out of the heart.^[4] Some people with hypertrophic cardiomyopathy don’t have symptoms in the early stages but develop them over time, which is why repeated monitoring becomes important if you have a family health history of this condition.^[5]

Even people who have no symptoms may experience what seems like unexplained tiredness or lack of energy, which they might attribute to aging or being out of shape. This is why knowing your family health history and discussing it with your healthcare provider becomes so important for early detection.

Steps You Can Take to Stay Healthy

While you cannot prevent the genetic changes that cause hypertrophic cardiomyopathy, you can take important steps to protect your health if you have a family history of the condition. The most crucial prevention strategy involves screening and early detection, particularly if someone in your family has been diagnosed with this heart condition or died suddenly at a young age.

If someone in your family has hypertrophic cardiomyopathy, that person should have genetic testing to look for the genetic changes that cause the condition.^[5] Testing should start with someone who has been diagnosed with the condition. Once the genetic change is found, other family members can have genetic testing for that same change. In cases where a young person died suddenly, genetic testing might have been done as part of the autopsy.

When genetic testing shows that you have the genetic change for hypertrophic cardiomyopathy, you will need to see a cardiologist, a doctor who specializes in heart conditions, to check your heart for signs of the disease.^[5] If the genetic change that causes hypertrophic cardiomyopathy in your family isn’t known, parents, siblings, and children of the person with the condition will need to be checked for signs of the disease through other testing methods.

It’s important to update your family health history information regularly and let your healthcare provider know about any new diagnoses, cardiac events, or sudden deaths in your family.^[5] This ongoing communication helps your doctor make informed decisions about your care and screening schedule.

Living a heart-healthy lifestyle plays a major role in managing your overall cardiovascular health, whether or not you have hypertrophic cardiomyopathy. This includes staying hydrated by drinking water throughout the day, following a heart-healthy diet, watching any cuts or scratches for signs of infection, and paying strict attention to dental hygiene, since untended gum infections can spread to the heart.^[15]

For those diagnosed with hypertrophic cardiomyopathy, prevention focuses on avoiding complications. Most people with the condition can benefit from light to moderate intensity recreational activity, such as walking, yoga, tai chi, and golfing.^[16] However, it’s essential to avoid intense bursts of exercise, heavy weightlifting, and competitive sports, as these can put dangerous strain on the heart. You should not lift heavy objects while performing household chores and should avoid environmental extremes like very hot or cold conditions.

How the Condition Changes Normal Heart Function

To understand how hypertrophic cardiomyopathy affects the body, it helps to know what happens in the heart when this condition develops. The disease is characterized by excessive thickening of the heart muscle, particularly in the left ventricle, which is the heart’s main pumping chamber.^[3] The thickening can happen anywhere in the left ventricle, though it most commonly affects the septum, the middle wall that divides the heart into left and right sides.

When the heart muscle becomes abnormally thick, several problems can occur. The thickened muscle can become stiff and sluggish, making it harder for the heart to relax and fill with blood between beats.^[7] This stiffness leads to what doctors call diastolic dysfunction, where the heart struggles to accept blood during its filling phase. Because the heart can hold less blood, the amount of blood pumped to the rest of the body with each heartbeat decreases.^[5]

There are two main types of hypertrophic cardiomyopathy, each affecting heart function differently. About 2 in 3 people with the condition have obstructive hypertrophic cardiomyopathy, where the thickened septum blocks or reduces blood flow from the left ventricle to the aorta, the body’s main artery.^[4] This obstruction forces the heart to work much harder to pump blood out to the rest of the body.

The other type is nonobstructive hypertrophic cardiomyopathy, where the heart muscle is thickened in other areas but doesn’t block blood flow out of the heart.^[4] Even without obstruction, the thickened muscle causes problems because it requires more energy and oxygen to work, especially during exercise.^[5]

The characteristic microscopic finding in hypertrophic cardiomyopathy is something called myocardial fiber disarray, where the normally organized heart muscle cells become chaotically arranged.^[11] This disorganization can affect the heart’s electrical system, leading to abnormal heart rhythms. The bundle branches that conduct electrical impulses through the septum and into specialized conducting fibers can be specifically affected, as these are responsible for coordinating the contraction of both ventricles.^[6]

The thickened heart muscle can also cause problems with the mitral valve, one of the heart’s four valves. This valve may not close properly, allowing blood to leak backward, a condition called mitral regurgitation.^[3] Additionally, because the heart requires more oxygen to function but the thickened muscle may not receive adequate blood supply, people can experience myocardial ischemia, where parts of the heart muscle don’t get enough oxygen.

People with hypertrophic cardiomyopathy can develop various complications over time. These include atrial fibrillation, which can lead to blood clots and stroke; congestive heart failure; infective endocarditis, an infection of the heart valves; dangerous ventricular arrhythmias; and sudden cardiac arrest.^[4] Understanding these potential complications helps explain why careful monitoring and appropriate treatment remain so important throughout a person’s life.