Healthy Living News

Gene for Heart Muscle Disease Found

by Howard LeWine, M.D.
Harvard Medical School

A single mutated gene causes more than 1 out of 4 cases of an inherited form of heart disease, new research suggests. The study focused on dilated cardiomyopathy. This disease causes the heart to stretch and get larger. The walls become thinner and less able to pump blood. The inherited form occurs in people who receive a mutated gene from just one parent. The new study included 312 people with dilated cardiomyopathy. No cause was known, so they were thought to have an inherited form. Researchers compared their DNA with two other groups of people. One group had a different disease, hypertrophic cardiomyopathy. People in the other group had healthy hearts. About 27% of people with inherited dilated cardiomyopathy had a mutation that shortened a gene known as TTN. Up to half of those with the mutation had a parent or sibling with the same mutation. Almost all of these relatives also had some sign of heart disease. Only 1% to 3% of the people in the comparison groups had these mutations. The New England Journal of Medicine published the study. HealthDay News wrote about it February 15.

What Is the Doctor's Reaction?

"You have a really big heart" is usually a wonderful compliment. But it's not something you want to hear from your doctor. An oversized heart usually isn't a good sign.

The heart can enlarge for many reasons. Common causes include:

• Coronary artery disease, especially with a history of prior heart attacks
• High blood pressure
• Overuse of alcohol
• Problems with the valves of the heart
• Viral infections

The heart can enlarge in two ways:

• Heart muscle cells can weaken and become flabby. The inside chambers of the heart get bigger. This is called dilated cardiomyopathy.
• The walls of one or both of the lower heart chambers (the left and right ventricles) can thicken. In athletes, this helps their performance. But in almost everyone else this is harmful. Instead of helping the heart pump more powerfully, the extra muscle may interfere with its function. This condition is called hypertrophic cardiomyopathy.

It's been known for many years that hypertrophic cardiomyopathy is mainly an inherited condition. Family members of people with this heart problem are told to get a test called an echocardiogram. The sound waves used in the test can detect if the walls of the lower heart chambers are abnormally thick.

Until recently, the inherited type of dilated cardiomyopathy was considered relatively rare. Scientists now know that gene mutations account for more cases than previously thought.

Only a few gene mutations had been linked with familial (inherited) dilated cardiomyopathy. They accounted for only a small minority of cases of inherited disease.

Now researchers from Harvard report results of a study that found a much more common gene problem. It's a mutation of the TTN gene. This gene provides instructions for the proteins in heart muscle cells needed for the heart to pump effectively. The New England Journal of Medicine published the study today.

The abnormal TTN gene that the researchers found is shorter than it should be. This leads to production of abnormal heart muscle cell proteins that weaken heart contractions. Over time, this can lead to heart failure.

The mutation appears to account for about 25% of inherited dilated cardiomyopathy. It also might cause up to 20% of dilated cardiomyopathy in people without family members known to have the disease.

What Changes Can I Make Now?

Heart failure is often a preventable disease, even for people who have the TTN mutation. We know this from today's research. Not everyone with the shorter TTN gene developed heart failure.

So whether or not you have this gene mutation, you can help prevent heart failure. Here's what you can do:

• Eat a healthy diet.
• Exercise regularly.
• Keep your blood pressure well within the normal range.
• Limit alcohol use to no more than two drinks per day for men and one drink per day for women.
• Maintain a healthy body weight.
• Don't smoke.

What Can I Expect Looking to the Future?

Family members of people known to have an inherited cause of dilated cardiomyopathy will likely get tested for TTN mutations in the future. Meanwhile, anyone with a family member suspected of this condition should get screened with an echocardiogram. Even if the echo is normal, the lifestyle choices you make can help you to avoid ever developing heart failure.

Categories: Heart Health

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