Association between Isometric and Allometric Height-indexed Left Atrial Size and Atrial Fibrillation.

Abstract Background Height-based indexations for evaluation of left atrial (LA) volumes have been proposed as an alternative method to account for body stature when body composition is abnormal. We sought to derive reference values for these indexation methods, and to examine their association to atrial fibrillation (AF). Methods A healthy population was randomly split into a derivation and validation cohort (n=493 each). The derivation cohort was used to derive reference values for iso- and allometric height-indexed LA volumes. Echocardiography included measurement of maximal and minimal LA volume (LAVmax and LAVmin, respectively). Association between these measures and AF was investigated in the validation cohort. Cox proportional hazards regression was performed adjusting for CHARGE-AF risk score. Results From 986 healthy subjects, allometric height-indexed exponents were determined to 1.72 and 1.56 for LAVmax and LAVmin, respectively. Upper reference values were determined to LAVmax>22.1mL/m1.72 and LAVmin>12.7mL/m1.56. In the validation cohort, 41 (8%) developed AF during follow-up (median: 14.7 years). In unadjusted analyses, both isometric and allometrically indexed LAVmax were associated with AF (HR=1.07 (1.03-1.11), p 22.1mL/m1.72 posed an increased risk of AF (HR=4.65 (1.83-11.86)), however, LAVmin>12.7mL/m1.56 carried a higher risk (HR=6.33 (2.66-15.07)). Conclusion Both Isometric and allometrically height-indexed LA volumes are associated with AF in the general population. LAVmin is more strongly associated with AF than LAVmax regardless of indexation.