Abstract: Objective To evaluate the left atrial substrate in patients with paroxysmal atrial fibrillation (PAF) using four-dimensional automated left atrial quantification (4D Auto LAQ). 
Methods A total of 59 patients with PAF who underwent voltage mapping of the left atrial substrate and radiofrequency ablation in the Second Hospital of Hebei Medical University were included in this study. Based on the voltage mapping results, patients were divided into the non-low voltage group (n=35) and the low voltage group (n=24). General clinical data, conventional echocardiogram parameters, left atrial strain and related parameters were compared between the two groups. The relevant factors were obtained by Logistic regression analysis. The parameters with the highest predictive value for left atrial low voltage and its cut-off value were determined by the area under receiver operating characteristic (ROC) area under curve (AUC). 
Results The mean age, CHA2DS2-VASc score, left atrial diameter (LAD), left atrial volume index (LAVI), left atrial maximal volume (LAVmax), left atrial minimal volume (LAVmin), and left atrial stiffness (LA stiffness) of the low voltage group were higher than those in the non-low voltage group. Left atrial total emptying fraction (LAEF), left atrial reservoir longitudinal strain (LASr), left atrial conduit longitudinal strain (LAScd), left atrial contraction longitudinal strain (LASct), left atrial reservoir circumferential strain (LASr-c), left atrial conduit circumferential strain (LAScd-c) and left atrial contraction circumferential strain (LASct-c) were lower in low voltage group than in the non-low voltage group (P＜0.05). Multivariate logistic regression analysis showed that after correcting for factors such as gender, the above indicators were still correlated with the presence or absence of low voltage, and the LASr had the highest predictive value (AUC=0.904, with the optimal cut-off value of 18.50%, sensitivity of 82.9%, and specificity of 83.3%). 
Conclusion LASr aids in non-invasive preoperative evaluation of left atrial substrate in PAF patients. 

Key words: atrial fibrillation, left atrial substrate, four-dimensional automated left atrial quantification, voltage mapping