Improvement of left atrial function is associated with lower incidence of atrial fibrillation and mortality after cardiac resynchronization therapy.

<bold>Background: </bold>Left atrial (LA) volume is a predictor of cardiovascular events in patients with heart failure. Improvement of LA function and reverse remodeling was observed after cardiac resynchronization therapy (CRT). <bold>Objective: </bold>The purpose of this study was to explore the clinical significance of improvement in LA function after CRT. <bold>Methods: </bold>Echocardiographic studies were performed before and 3 months after CRT in 97 patients (72 men and 25 women; age 63.8 +/- 13.3 years) with standard CRT indication but no history of atrial fibrillation (AF). LA active emptying fraction based on the change in volumes (LAV-EF) were calculated, and significant improvement in LA function (LA responder) was defined as a relative increase >/=50% from baseline LAV-EF. The primary end-points were newly developed AF detected by ECG or device and all-cause mortality. <bold>Results: </bold>After 1,200 +/- 705 days of follow-up, LA responders (n = 47 [48.5%]) had a significantly lower incidence of AF (12.8% vs 40%, P = .002) and mortality (17% vs 44%, P = .004) than did LA nonresponders. In Cox proportional hazard analysis, LA responders was the only independent predictor of lower risk of new-onset AF (hazard ratio 0.22, 95% confidence interval 0.08-0.61, P = .003), whereas both LA responders (hazard ratio 0.22, 95% confidence interval 0.09-0.53, P <.001) and left ventricular reverse remodeling (>10% reduction in left ventricular end-systolic volume at 3 months; hazard ratio 0.96, 95% confidence interval 0.93-0.99, P = .03) were independent predictors of lower risk of death after CRT. <bold>Conclusion: </bold>Improvement of LA function after CRT was associated with a lower incidence of AF and mortality in AF naïve patients with severe heart failure. [ABSTRACT FROM AUTHOR]