Background: Atrial cardiomyopathy is known as an underlying pathophysiological factor in the majority of AF patients. Left atrial low-voltage areas (LVAs) are reported to coincide with fibrosis, and to likely represent atrial cardiomyopathy. This study aimed to delineate differences in the long-term prognosis of patients stratified by the size of LVAs. Methods: This observational study included 1,488 consecutive patients undergoing initial ablation for AF. LVAs were defined as regions with a bipolar peak-to-peak voltage of < 0.50 mV. The total study population was divided into 3 groups stratified by LVA size: patients with no LVAs (n=1136), those with small (< 20 cm2, n=250) LVAs, and those with extensive (≥ 20 cm2, n=102) LVAs. Composite endpoints of death, heart failure, and stroke were followed for up to 5 years. Results: Composite endpoints developed in 105 (7.1%) of 1488 patients, and AF recurrence occurred in 410 (27.6%). Composite endpoints developed more frequently in the order of patients with extensive LVAs (19.1%), small LVAs (10.8%), and no LVAs (5.1%; p for trend<0.0001). Multivariable analysis revealed that LVA presence was independently associated with higher incidence of composite endpoints, irrespective of AF recurrence (modified hazard ratio=1.73, 95% confidence interval=1.13-2.64, p=0.011) Conclusions: LVA presence and its extent were both associated with poor long-term composite endpoints of death, heart failure, and stroke, irrespective of AF recurrence or other confounders. Underlying atrial cardiomyopathy appears to define a poor prognosis after AF ablation.