Abstract Body (Do not enter title and authors here): Background: Atrial fibrillation (AF), both new-onset and preexisting, is linked to increased mortality in acute pulmonary embolism (APE). The causal pathway for this association, whether through increased right ventricular dysfunction (RVD) is less well understood.

Hypothesis: AF independently predicts RVD in APE patients, affecting mortality and clinical outcomes.

Goals:
Examine the relationship between AF and RVD to understand its impact on APE survival.
Guide further research into optimal APE therapeutic strategies, focusing on early rhythm control.

Methods: We conducted a retrospective, multi-center cohort study using data from our Pulmonary Embolism Response Team (PERT) registry. Inclusion criteria included PERT activation and adults over 18. Exclusions were for missing transthoracic echocardiogram (TTE) within 3 days or incomplete TTE data. Patients were categorized by AF status, with RVD assessed by TTE markers. Analysis involved logistic regression and Cox proportional hazards models.

Results: Among 535 APE patients, 15% had AF. These patients showed higher unadjusted RVD rates (56% vs. 39%, p=0.006) and significant differences in TTE parameters: TAPSE (1.72 vs. 1.89 cm, p=0.007), S` (11.5 vs. 13.4 cm/s, p=0.0002), and RVOT VTI (13 vs. 14 cm, p=0.019). Adjusted analyses confirmed AF's significant association with RVD (OR 2.32, CI 1.3-4.1), inpatient mortality (OR 4.9, CI 1.5-17, p=0.0106), acute renal failure (OR 2.2, CI 1.2-4.1, p=0.0102), and one-year mortality (HR 1.9, CI 1.06-3.44, p=0.03).

Conclusions: AF significantly influences mortality in APE, partly through increased RVD. These findings underline the need for further studies to confirm these relationships and enhance treatment strategies.