In hypertrophic cardiomyopathy, the heart muscle cells have enlarged and the walls of the heart chambers thicken.
The chambers are reduced in size so they can’t hold much blood, and the walls can’t relax properly and may stiffen.
Most people with hypertrophic cardiomyopathy will be able to live a full, normal life. Some people don’t even have symptoms and don’t need treatment.
But that doesn’t mean the condition can’t be serious. Hypertrophic cardiomyopathy is the most common cause of sudden unexpected death in childhood and in young athletes.
The main heart chambers can become stiff, leading to back pressure on the smaller collecting chambers. This can sometimes worsen the symptoms of heart failure and lead to abnormal heart rhythms (atrial fibrillation).
Blood flow from the heart may become reduced or restricted (known as obstructive hypertrophic cardiomyopathy).
Also, the mitral heart valve can become leaky, causing blood to leak backwards. Read more about mitral regurgitation.
These heart changes can cause dizziness, chest pain, shortness of breath and temporary loss of consciousness.
You’ll also be at greater risk of developing endocarditis (a heart infection).
If you have severe hypertrophic cardiomyopathy, you’ll need to see your doctor regularly so your condition can be monitored.
Your doctor will advise about the level and amount of exercise you can do and sensible lifestyle changes to make.
Hypertrophic cardiomyopathy is thought to affect 1 in 500 people in the UK. Most people inherit the disease from their parents.
Read more about how genetic conditions are inherited.
Read the British Heart Foundation and Cardiomyopathy UK booklet on living with hypertrophic cardiomyopathy.