The Link Between AFib and Epicardial Fat
The Link Between AFib and Epicardial Fat
The heart has a layer of fat around it, called epicardial fat, which is generally a good thing. In healthy hearts, these lipids can provide energy and other support, but having too much fat is associated with a form of irregular heartbeat called atrial fibrillation (AFib), a common type of heart failure in the elderly. AFib is commonly treated with a minimally invasive procedure called ablation, using a thin wire introduced through a vein in the patient’s groin. The wire delivers energy to the heart to create tiny scars in the heart tissue that causes AFib. While the standard ablation approach is effective in many patients, a fair number of patients experience recurrences of AFib that require additional and/or alternative treatment.
“There are a number of studies that have shown recurrence rates after ablation are higher in people with more epicardial fat,” said Jeffrey Goldberger, M.D., professor of cardiovascular medicine, who directs the University of Miami Health System’s Center for Atrial Fibrillation.
To help overcome this, Dr. Goldberger, along with Gianluca Iacobellis, M.D., Ph.D., professor of clinical medicine, and colleagues conducted the LEAF (Liraglutide Effects in Atrial Fibrillation) study, which tested whether patients taking a GLP-1 (liraglutide) weight-loss medication before their ablations would have better results.
“We used three months of treatment, and then we proceeded with the ablation,” Dr. Goldberger said. “We found that the ablation outcomes in the liraglutide-plus-risk-factor-modification group were dramatically better than the outcomes with risk-factor modification alone.”
The study also hinted that GLP-1 drugs could beneficially modify epicardial fat. During childhood, there is a relatively high proportion of brown fat, which is protective. As people age, brown fat diminishes. GLP-1s might bring it back.
“When we activate GLP-1 receptors in epicardial fat, it boosts the genes coding for brown fat,” Dr. Iacobellis said. “We need to investigate more, but this could potentially take epicardial fat back into its infancy.”
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This is just the start. Dr. Goldberger and colleagues received an NIH grant to study how epicardial fat contributes to AFib. The team will investigate the molecular mechanisms — genes, proteins and metabolites — to better understand how this adipose tissue can influence AFib.
“In other organs, there’s a membrane between the tissue and the surrounding fat, but not so with the heart,” Dr. Iacobellis said. “Epicardial fat has extremely active signaling molecules, and that lack of a barrier between the two tissues means they go directly into the heart, and that’s why there is this strong interaction.”
The team also found the blood composition in the heart can be quite different from the peripheral blood taken from veins. Lina Shehadeh, Ph.D., research professor of cardiovascular medicine, has been analyzing these different samples and has come up with some interesting findings.
“The blood from the atrium shows a lot of lipase, an enzyme that breaks down lipids,” Dr. Shehadeh said. “This means there are lots of lipids in the atria, and people with AFib may have abnormal beating because their metabolism, the process of generating energy, is dysregulated.”
This collaboration between researchers and clinicians allows the team to work synergistically to find answers. Results in patients give Drs. Iacobellis, Shehadeh and others clues to where they should take the research. The ultimate goal is to better understand AFib and develop more focused interventions.
“Atrial fibrillation is not one disease; it’s a syndrome,” Dr. Goldberger said, “and unless we come up with a more personalized way of addressing that, we’re not going to do better. Our focus is to find personalized medicine approaches for patients with AFib.”
“Atrial fibrillation is not one disease; it’s a syndrome, and unless we come up with a more personalized way of addressing that, we’re not going to do better. Our focus is to find personalized medicine approaches for patients with AFib.”
