Left Atrial Expansion Index Predicts Atrial Fibrillation in Dyspnea

Background: The left atrial (LA) expansion index for predicting atrial fibrillation (AF) in a relatively low-risk cohort is not fully understood. Methods and Results: In this prospective study of 2,200 dypnea patients, the LA expansion index was calculated as (Vol(max)-Vol(min))x100%/Vol(min), where Vol(max) was defined as maximum LA volume and Vol(min) was defined as minimum volume. The endpoints were 2-year frequency of AF, including both paroxysmal and persistent. Of the 180 participants (8.2%) who had AF attacks over a median follow-up of 2.7 years, 90 (4.1%) had at least 1 episode of persistent AF. Compared to patients with paroxysmal AF, those with persistent AF had a much lower LA expansion index (100 +/- 59% vs. 44 +/- 24%). LA expansion index was associated exponentially with the incidence of persistent AF. Independent predictors of AF included age, renal function impairment, pulmonary artery systolic pressure, and LA expansion index. Persistent AF, however, had significant independent associations only with prior heart failure, renal function impairment, diastolic dysfunction, and LA expansion index (odds ratio, 0.970; 95% confidence interval: 0.959-0.981 per 1% increase, P<0.0001). Compared to other parameters, LA expansion index <61.4% was the best cut-off point to predict persistent AF. Conclusions: The LA expansion index is associated with the presence of AF, and a reduced LA expansion index has a strong association with persistent AF.