Postoperative Atrial Fibrillation (POAF) after Cardiac Surgery Postoperative atrial
fibrillation is a common complication following cardiac surgery, characterized by
irregular and often rapid heart rate. It is associated with increased morbidity,
prolonged hospital stays, and higher healthcare costs. The pathophysiology of POAF is
complex and multifactorial, involving atrial structural and electrical remodeling,
inflammation, and autonomic dysregulation.
Inflammation and Epicardial Fat Inflammation plays a significant role in the development
of POAF. Surgical trauma and cardiopulmonary bypass trigger a systemic inflammatory
response, releasing cytokines and other inflammatory mediators. Epicardial fat, the
visceral fat depot around the heart, is an active endocrine organ secreting
pro-inflammatory cytokines and adipokines. Increased epicardial fat thickness is
associated with higher levels of inflammation and has been implicated in the pathogenesis
of atrial fibrillation.
RNA isolation and sequencing RNA sequencing (RNA-seq) can be used to investigate gene
expression in epicardial fat in several impactful ways. RNA-seq can profile gene
expression to identify active genes in epicardial fat and their expression levels,
revealing key genes involved in inflammation and metabolism. By comparing gene expression
between groups, such as patients with and without POAF, RNA-seq can identify
differentially expressed genes associated with atrial fibrillation.
RNA-seq analyses The RNA sequencing data files were aligned to the hg38 reference genome
using the Spliced Transcripts Alignment to a Reference (STAR) aligner and read counts in
genes were quantified. The resulting data matrix with unnormalized counts was loaded into
RStudio together with patient metadata information (e.g., age, gender, BMI, smoking).
Differential expression analyses were conducted with DESeq2 using adjustment for
different variables, including type of tissue, age of patients, gender, and BMI.
Hypothesis The hypothesis that POAF may be influenced by pre-existing inflammation in
epicardial fat, in addition to the inflammation caused by surgical trauma.
Objective:
To compare inflammatory gene expression in epicardial fat between patients who develop
POAF and those who do not after elective cardiac surgery.
Study Design:
A prospective cohort study including patients undergoing first-time elective cardiac
surgery.
Participants:
Inclusion criteria: Patients undergoing first-time elective cardiac surgery. Exclusion
criteria: Patients with previous cardiac surgeries or emergency surgeries.
Groups:
POAF Group: Patients who develop POAF. Non-POAF Group: Patients who do not develop POAF.
Sample Collection:
Epicardial fat samples will be collected during the time of surgery.
RNA Isolation and Sequencing:
Homogenize adipose tissue in TRIzol using ceramic beads (Fastprep 24, MPBio). Purify RNA
using EconoSpin columns (Epoch). Prepare RNA libraries with NEBNext Ultra II RNA Library
Prep Kit for Illumina. Perform paired-end sequencing on the NovaSeq 6000 platform
(Illumina).
Data Analysis:
Align RNA-seq data to the hg38 genome using STAR aligner. Quantify gene counts and
perform differential expression analysis using DESeq2. Adjust for variables such as
tissue type, age, gender, and BMI.
Outcome Measures:
Compare inflammatory gene expression profiles between POAF and Non-POAF groups at the
time of surgery.
