Abstract 16011: Prospective Associations of Left Atrial Size and Function With Cardiovascular Disease in American Indians: The Strong Heart Study

Introduction: Left atrial (LA) volume is associated with incident cardiovascular disease (CVD) in studies involving referral populations. Fewer studies have examined the association of measures of LA function with CVD events in community-based cohorts without clinically apparent disease. Methods: We investigated the relations and predictive value of LA volume index (LAVI=LA volume/body surface area), LA emptying fraction (LAEF= [Max LA Volume - Min LA Volume]/Max LA Volume) and LA function index (LAFI=[LAEFxLV outflow tract velocity time integral]/LAVI) with CVD events (coronary heart disease, stroke, heart failure) in a population-based cohort study of American Indians with high prevalences of obesity and diabetes. We excluded participants with clinical CVD, atrial fibrillation and Echo valvular disease, leaving 2,753 participants for analysis (age 59±8 years, 65% women). Stored Echos were reviewed in a random subset of 2,128 participants, 1,899 of whom had measurable maximal and minimal LA volumes. LA volume was measured using the modified biplane area-length method. Results: During median f/u of 13.5 yrs, 595 CVD events occurred. After adjustment for age, sex, BMI, systolic BP, hypertensive medication, diabetes, smoking, total and HDL cholesterol, eGFR, albuminuria, CRP, and LA diameter, LAVI (HR per SD increment 1.12, 95% CI 1.01-1.23) and LAFI (HR per SD decrement 1.19 [1.08-1.32]) were significantly associated with CVD events, but LAEF was not (HR per SD decrement 1.09 [0.99-1.19]). These risk estimates were unchanged after additional adjustment for LV mass index, LV regional or global function, transmitral E/A, and MAC. LAVI and LAFI modestly improved risk prediction when added to a clinical model (c-index 0.767 and 0.768, respectively, vs. 0.761), as well as a model containing clinical and other Echo predictors (c-index 0.776 and 0.777 vs. 0.771). Addition of LAFI to LAVI in the latter model, however, did not further improve prediction (c-index 0.777 vs. 0.776). Conclusion: In this sample of American Indians, LAVI and LAFI were associated with CVD independent of clinical risk factors, LA diameter, and other Echo predictors. Both measures improved risk prediction, although there was no evidence of incremental value when LAFI was added to LAVI.