Abstract Body (Do not enter title and authors here): Background:
Atrial fibrillation (AF) and mitral valve regurgitation (MVR) often co-occur in clinical settings, with the temporal sequence of their diagnoses potentially influencing cardiovascular outcomes. This study aimed to compare major cardiovascular event risks in patients diagnosed first with MVR followed by AF (MVR→AF) versus those with the reverse sequence (AF→MVR).

Methods:
A retrospective comparative outcomes analysis was conducted using the TriNetX Global Collaborative Network, encompassing data from 135 healthcare organizations. Two cohorts were defined post–propensity score matching using demographic, comorbidities, procedures and treatment: Cohort 1 (MVR→AF; n = 111,391) and Cohort 2 (AF→MVR; n = 111,391). Patients were balanced across demographics and comorbidities to isolate outcome differences. Cardiovascular outcomes were compared via later Cox models to obtain the hazard ratios (HRs) with 95% confidence intervals (CIs) (table 2).

Results:
Despite similar baseline characteristics, the MVR→AF group exhibited significantly higher incidence rates of all evaluated cardiovascular outcomes. Major Adverse Cardiovascular Events (MACE) occurred in 28.3% of MVR→AF patients compared to 21.0% in the AF→MVR cohort (HR 1.30; 95% CI: 1.28–1.33; p < 0.0001) (Figure 1). This trend persisted across subcategories including ischemic heart disease (HR 1.18), heart failure (HR 1.38), myocardial infarction (HR 1.41), and cerebrovascular outcomes such as cerebral infarction (HR 1.35) and TIA (HR 1.31). The most notable disparity was observed in acute coronary disease (HR 1.65; p = 0.028). Cardiogenic shock and cardiac arrest, while elevated in the MVR→AF group, did not reach statistical significance (table 2).

Conclusion:
Patients with MVR preceding AF diagnosis are at significantly higher risk for adverse cardiovascular outcomes compared to those with AF diagnosed prior to MVR. These findings underscore the need for heightened surveillance and potential early intervention strategies in the MVR→AF population to mitigate downstream cardiovascular morbidity.