Measurements of LA volume: All LA volume measurements will be calculated from apical 4- and 2-chamber views using the biplane area-length method (15). The LA volumes are measured at 3 points: 1) immediately before the mitral valve opening (maximal LV volume or Volmax); 2) at onset of the P-wave on electrocardiography (pre-atrial contraction volume or Volp); and 3) at mitral valve closure (minimal LV volume or Volmin). The LA distensibility was calculated as (Volmax - Volmin) / Volmin. The LA ejection fraction is calculated as (Volp - Volmin) / Volp. In all patients, LA volumes are indexed to body surface area (BSA).