Moderate-to-Vigorous Intensity Physical Activity and Risk of Incident Atrial Fibrillation in Atrial Cardiomyopathy.

BACKGROUND: Current guidelines recommend physical activity for atrial fibrillation (AF) prevention, yet its role in individuals with atrial cardiomyopathy (AtCM) remains unclear. OBJECTIVES: We investigated the association between accelerometer-measured moderate-to-vigorous intensity physical activity (MVPA) and incident AF according to AtCM status. METHODS: Among 10,003 UK Biobank participants, AtCM was identified via multimodal approach integrating cardiovascular magnetic resonance imaging and 12-lead electrocardiography. Multivariable adjusted Cox proportional hazards models assessed the association between 7-day accelerometer-measured MVPA and incident AF. An interaction term evaluated substrate-specific associations. RESULTS: AtCM was identified in 4.5% of participants. Over a median follow-up of 3.2 years, AtCM was associated with an increased risk of AF (HR: 3.01; 95% CI: 1.69 to 5.37). AtCM status significantly modified the MVPA-AF association (P for interaction = 0.029). Without AtCM, MVPA showed marginal risk reduction (HR per 10-minute increase: 0.94; 95% CI: 0.87-1.01). Conversely, with AtCM, MVPA was strongly associated with a lower AF risk (HR per 10-minute increase: 0.76; 95% CI: 0.62-0.93). The absolute risk reduction was 2.82 AF events per 1,000 person-years for every 10-minute increase in MVPA in the AtCM group, significantly greater than without AtCM (difference: -2.66; 95% CI: -4.32 to -0.73; P = 0.011). Findings remained robust across comprehensive sensitivity analyses. CONCLUSIONS: MVPA demonstrated a robust inverse association with incident AF risk, particularly in individuals with AtCM. Identifying subclinical atrial substrate may guide targeted physical activity recommendations, suggesting MVPA as a potent lifestyle intervention to attenuate the transition from subclinical remodeling to overt clinical arrhythmia.