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RNA molecules predict adverse heart growth and function that can lead to atrial fibrillation and death

Researchers have identified that enlargement of the left atrium of the heart is linked to abnormal activity of molecules that are associated with adverse changes in the heart’s size, shape, structure, and function — conditions that can lead to atrial fibrillation and death.

The new study, conducted by researchers at the Intermountain Medical Center Heart Institute in Salt Lake City, is the first time this association has been connected to the human heart in a clinical setting.

In conducting the study, researchers noted that under stress conditions, cardiac fibroblasts, which play a role in normal cardiac function and changes in the heart, release greater quantities of exosomes, which are small pieces of cells circulating in the blood that contain cellular components and convey information to distant tissues.

The Intermountain Medical Center Heart Institute researchers found that in patients with atrial fibrillation, exosomes and plasma are enriched with MicroRNA (miR)-21-3p — which is associated to abnormal enlargement of the heart muscle.

Scientists are interested in exosomes because initially they were thought to be a waste by-product as cells shed. But now researchers are learning that not only are exosomes communicators between cells, but they influence the spread of proteins, lipids, mRNA, miRNA, and DNA and are contributing factors in the development of several diseases.

“Our study gives us a better understanding of the process of how atrial fibrillation begins and advances,” says Victoria Jacobs, NP, PhD, a member of the Intermountain Medical Center Heart Institute research team. “Once atrial fibrillation happens, we have some ‘band-aids’ to fix its symptoms, but we want to learn how to keep atrial fibrillation and atrial enlargement from happening in the first place.”

While an enlarged atria may have several causes, recent studies have linked enlargement to an increased risk of atrial fibrillation. Researchers are interested in learning more about atrial fibrillation because it, along with coronary artery disease, is the number one killer of people in America. Atrial fibrillation affects more than 3.4 million Americans, primarily older adults.

An enlarged left atrium has been linked to atrial fibrillation, as it can prevent the heart from pumping blood properly and may increase risk of an irregular heartbeat.

Researchers at the Intermountain Medical Center Heart Institute examined biomarkers, which are biological molecules used to see how well the body responds to a treatment for a disease or condition, that could specifically predict the occurrence and severity of adverse growth in the left atrium of the heart. A basic study previously done in Germany that focused on cell cultures and small lab rodents suggested that miR-21-3p played a role in that growth. But no one has connected it to the human heart in a clinical setting until now.

“We know patients with atrial fibrillation develop thickening of heart tissue, or fibrosis,” said Dr. Jacobs. “As atrial fibrillation progresses, we know there’s more fibrosis in the left atrium. But this is the first time we’ve shown miR-21-3p is associated with left atrial fibrillation in patients.”


The Intermountain Medical Center