Exosome plays an important role in the pathophysiology of the cardiovascular system. Since the field of cardiovascular exosome is still in its infancy, there are no available data regarding to its role in cardiac arrhythmias. The current study investigates the role of epicardial fat derived exosomes in patients who suffer from atrial fibrillation.

Myocardial cells communication is mediated via direct cell to cell contact, cell to matrix interaction, long-range signals, electrical signals, and via extracellular chemical molecules (such as proteins, nucleotides, lipids and short peptides). Cell to cell communication can be achieved through direct contact (i.e. Gap junction, cell surface protein/protein interaction) or via secreted signaling molecules (i.e. hormones, neurotransmitters, cytokines). In the last few decades, a third intercellular communication mechanism has gained intense attention - extracellular vesicles that include: (1) apoptotic vesicles (1000-4000 nm), (2) microvesicles (100 nm - 1000 nm), and the smallest extracellular vesicles (3) exosomes (40-100 nm).

The exosomes are produced through the endosomal pathway and are able to carry cargo and transfer them to recipient cells, thus contributing to cell-to-cell communication. The exosomes cargo includes protein content, rRNA, tRNA, short DNA sequences, messenger RNA (mRNA) and microRNA (miRNA). The last two can change the gene expression within the target cells and by that affect myocardial cells.

Nowadays, it is known that in the cardiovascular system, exosome plays important roles in the pathophysiology of myocardial infarction (MI) and as an indicator for the damage and repair mechanisms post-acute MI (i.e. miR-126), in myocardial remodeling, and cardiac regeneration.

Since the field of cardiovascular exosome is still in its infancy, there are no available data regarding to its role in cardiac arrhythmias. Therefore, there is place to investigate the role of exosomes in patients who suffer from atrial fibrillation.

Some of the important issues to explore are: (1) Do the epicardial fat in patients with atrial fibrillation release quantitatively and qualitatively different exosomes than in patients without atrial fibrillation? (2) Can epicardial fat exosomes be a clinical biomarker for arrhythmias? (3) Can these exosomes be a target for the treatment and prevention of arrhythmias?

The current study will include patients who undergo any cardiac surgery and will give informed consent. An epicardial fat biopsy will be taken and cultured in a medium that contain M-199 medium, dexamethasone, gentamicin, and insulin for 9 days. The exosomes will be collected from the medium and analyzed.

The participants will be divided into two groups: (1) participants with atrial fibrillation, (2) participants who did not develop ever atrial fibrillation.

Inclusion Criteria:

• Age ≥ 18 years
• Undergoing an elective cardiac surgery

Exclusion Criteria:

• Undergoing a non-elective surgery
• Suffering from severe renal impairment prior to surgery (creatinine clearance <30 mL/min)
• Experienced hepatic dysfunction other than mild

Results: The exosomes content in patients with and without atrial fibrillation