Do the left atrial substrate properties correlate with the left atrial mechanical function? A novel insight from the electromechanical study in patients with atrial fibrillation

Atrial Fibrillation and Atrial Mechanical Function. Background: The atrial substrate is the determinant of occurrence and maintenance of atrial fibrillation (AF), which can induce remodeling of atrial function and structure. This study investigated the relationship between the left atrial (LA) substrate properties and LA mechanical function. Methods: Forty-four consecutive patients (50.3 ± 10.7 years old, 33 men) who presented with sinus rhythm during echocardiographic study before receiving catheter ablation for AF were enrolled. The LA diameter, LA volume, ratio of early and late transmitral filling flow velocities (E/A), LA appendage flow velocity, and transmitral velocity-time integral (VTI) were measured by the echocardiography. The LA empty fraction (LAEF), which was obtained via dividing the difference between maximal and minimal LA volume by maximal LA volume, was calculated as a parameter of the global LA contractile function. The LA global contact voltage mapping (NavX system) was performed before pulmonary vein isolation. Results: Mean LA voltage and LA low voltage zone index (LVZ index, area with voltage < 0.5 mV, divided by total LA surface area) showed significant correlation with LA diameter and volume, but only the LA LVZ index showed significant correlation with A-wave velocity, transmitral A-wave VTI, and LAEF (r = -0.340, -0.411, -0.426; P = 0.024, 0.006, 0.005, respectively). We divided the LA LVZ index into three groups (< 10%, 10-20%, > 20%). The LAEF got worse and the transmitral A-wave VTI percentage (divided by transmitral VTI) decreased as LA LVZ index increased. Conclusions: The LA substrate properties showed close correlation with LA size, but only the LA LVZ index correlated with the LA mechanical function.