Abstract Body (Do not enter title and authors here): Introduction:
Inflammation and fibrinogenesis in the left atrium are hypothesized to play a major role in the development of atrial fibrillation (AF). We previously showed that collagen metabolism biomarkers (CMB) are significantly elevated in patients with AF compared to healthy controls.

Objective:
We sought to investigate the relationship between CMB, Left Atrial Fibrosis (LAF) and AF recurrence after ablation.

Methods:
Patients with AF undergoing ablation evaluation (N= 96) were prospectively enrolled between 2015 – 2020. Plasma samples were collected prior to ablation and analyzed for CMB using commercially available ELISA kits. Sixty-four patients underwent AF ablation and were followed for 6 months for AF recurrence. CMR was performed in 48 patients using cine and 3D high resolution, late gadolinium enhancement imaging on 3T MRI to measure LAF. Patients were classified into 2 groups dichotomized by the median LAF value.

Results:
Mean age was 60.3 ± 10.3 years, mean BMI 29.7 ± 4.9 kg/m2, mean CHA2DS2-VASc score 1.9 ± 1.4 and 27% were women. Paroxysmal AF was present in 52.5%. The median LAF score was 13.6% (IQR 9.8 – 21.7). High PINP, high CITP and low TIMP-2 were associated with high LAF score (Table 1). High CITP was also associated with recurrence of AF after ablation {4.26 ng/ml (IQR 3.22 - 4.65) vs 3.26 ng/ml (IQR1.92 - 4.25), P = 0.02}.

Conclusion:
Higher levels of PINP and CITP were significantly associated with higher LAF score in AF patients. TIMP-2 was associated with low LAF. Higher CITP was also associated with AF recurrence after ablation. Further larger studies are needed to better understand the relationship between collagen biomarkers, LA fibrosis and their clinical impact on rhythm control in AF.