Hypertrophic Cardiomyopathy

Hypertrophic cardiomyopathy (HCM) is a complex type of heart disease that affects your heart muscle. It can cause:

• Thickening of your heart muscle (especially the ventricles or lower heart chambers).
• Left ventricular stiffness.
• Mitral valve changes.
• Cellular changes.

How does hypertrophic cardiomyopathy (HCM) affect my body?

Thickening of the heart muscle (myocardium)

This occurs most commonly at your septum. The septum is the muscular wall that separates the left and right sides of your heart. Problems happen when the septum between your heart’s lower chambers (or ventricles) is thickened.

The thickened septum may cause a narrowing that can block or reduce the blood flow from the left ventricle to the aorta — a condition called outflow tract obstruction. The ventricles must pump harder to overcome the narrowing or blockage. This type of hypertrophic cardiomyopathy may be called hypertrophic obstructive cardiomyopathy (HOCM).

HCM also may cause thickening in other parts of your heart muscle, such as the bottom of your heart (called the apex), right ventricle or throughout your entire left ventricle. In these cases, it’s called hypertrophic nonobstructive cardiomyopathy. Although this type reduces the amount of blood your ventricle can handle, it doesn’t keep blood from moving.

Stiffness in the left ventricle

This occurs as a result of cellular changes that happen in your heart muscle when it thickens. Your left ventricle can’t relax normally and fill with blood. Since there’s less blood at the end of filling, there’s less oxygen-rich blood pumped to your organs and muscles. The stiffness in your left ventricle causes pressure to increase inside your heart and may lead to symptoms such as:

• Chest pain.
• Difficulty breathing (shortness of breath).
• Dizziness or fainting.
• Feeling that your heart’s beating too fast (palpitations).

Mitral valve changes

When your left ventricular outflow tract becomes narrow, your mitral valve doesn’t work properly. This blocks outflow (obstruction) and increases pressure in your left ventricle.

The blockage (obstruction) is the result of your mitral valve striking your septum. When this occurs, your mitral valve frequently leaks, causing the blood to go back into your left atrium.

Cellular changes (changes in the cells of the heart muscle)

Through a microscope, heart muscle cells look disorganized and irregular (disarray) instead of being organized and parallel. This disarray may cause changes in the electrical signals traveling through the lower chambers of your heart and lead to a type of abnormal heart rhythm called ventricular arrhythmia.

How common is hypertrophic cardiomyopathy (HCM)?

Hypertrophic cardiomyopathy affects an estimated 600,000 to 1.5 million Americans or 1 in 500 people. It’s more common than multiple sclerosis, which affects 1 in 700 people.

How old are people when they get hypertrophic cardiomyopathy (HCM)?

This heart problem often shows up during the teen years, but it can start at other ages.

Can I get pregnant if I have hypertrophic cardiomyopathy (HCM)?

Although pregnant people with hypertrophic cardiomyopathy may need specialized care, such as echocardiography, most can support pregnancy and have a vaginal delivery. If you’re considering becoming pregnant, discuss your risks with your healthcare provider. Your provider can tell you which medicines for hypertrophic cardiomyopathy you can keep taking during your pregnancy. You may also be able to get a pacemaker or an implantable cardioverter defibrillator (ICD) if you need one during pregnancy.