4325Change in left atrial function predicts incident atrial fibrillation: the multi-ethnic study of atherosclerosis
Authors: Lim D , Ambale-Ventakesh B , Ostovaneh M , Zghaib T , Ashikaga H , Wu C , Watson K , Hughes T , Shea S , Heckbert S , Bluemke D , Post W , Lima J 
Published: October 2019

Abstract

Background
Longitudinal change in left atrial (LA) structure and function could be helpful in predicting risk for incident AF. We used cardiac magnetic resonance (CMR) imaging to explore the relationship between change in LA structure and function and incident AF in a multi-ethnic population free of clinical cardiovascular disease at baseline.

Methods and results
In the Multi-Ethnic Study of Atherosclerosis (MESA), 2338 participants, free at baseline of clinically recognized AF and cardiovascular disease, had LA volume and function assessed with CMR imaging, at baseline (2000–02), and at Exam 4 (2005–07) or 5 (2010–12). Free of AF, 124 participants developed AF over 3.8±0.9 years (to 2015) following the second imaging. In adjusted Cox regression models, an average annualized change in all LA parameters were significantly associated with an increased risk of AF. An annual decrease of 1–SD unit in total LA emptying fractions (LAEF) was most strongly associated with risk of AF after adjusting for AF clinical risk factors, baseline LA parameters and left ventricular mass-to-volume ratio (hazard ratio per SD=1.91,95% confidence interval=1.53–2.38, P<0.001). The addition of change in total LAEF to an AF risk score improved model discrimination and reclassification (net reclassification improvement=0.107, P=0.017; integrative discrimination index=0.049, P<0.001).
Model discrimination, NRI and IDI Model: CHARGE-AF risk factors# + Baseline LA variable + ΔLA variable CHARGE-AF ΔLAVImin (mL/m2/y) ΔTotal LAEF (%/y) ΔPeak LA Strain (%/y) C-statistic (95% CI) 0.757 (0.721–0.794) 0.787 (0.749–0.824) 0.779 (0.737–0.820) 0.770 (0.732–0.808) NRI† (p-value) – 0.000 (0.991) 0.107 (0.017) 0.017 (0.634) IDI (p-value) – 0.049 (<0.001) 0.049 (<0.001) 0.018 (<0.001) Calibration chi2* (p-value) 19.3 (0.02) 11.68 (0.232) 5.751 (0.765) 3.673 (0.932) AF: atrial fibrillation; LA: left atrium; EF: emptying fractions; Δ: annual change; VImin: minimum indexed volume; CI: confidence interval; NRI: net reclassification improvement; IDI: integrative discrimination index #CHARGE-AF risk factors: age, race, height, weight, systolic and diastolic blood pressure, use of antihypertensive medication, smoking status, diabetes, MI and CHF by the second imaging. † Categories for NRI: <2.5%, 2.5%-5% and >5%. *Model calibration: Grønnesby and Borgan's modified Hosmer-Lemeshow chi-square statistic for survival analysis.
Kaplan-Meier curves of ΔTotal LAEF

Conclusion
In this multi-ethnic study population free of clinical cardiovascular disease at baseline, a greater increase in LA volumes and decrease in LA function were associated with incident AF. The addition of change in total LAEF to risk prediction models for AF improved model discrimination and reclassification of AF risk.

Acknowledgement/Funding
This research was supported by contracts HHSN2682015ehz745.01623I,N01-HC-95159-69 from the NHLBI and UL1-TR-ehz745.016240,UL1-TR-001079,R01-HL-127659 from NIH