Normal 2-Dimensional Strain Values of the Left Ventricle: A Substudy of the Normal Echocardiographic Measurements in Korean Population Study

Background: It is important to understand the distribution of 2-dimensional strain values in normal population. We performed a multicenter trial to measure normal echocardiographic values in the Korean population. Methods: This was a substudy of the Normal echOcardiogRaphic Measurements in KoreAn popuLation (NORMAL) study. Echocardiographic specialists measured frequently used echocardiographic indices in healthy people according to a standardized method at 23 different university hospitals. The strain values were analyzed from digitally stored images. Results: Of a total of 1003 healthy participants in NORMAL study, 2-dimensional strain values were measured in 501 subjects (265 females, mean age $47{\pm}15$ years old) with echocardiographic images only by GE echocardiographic machines. Interventricular septal thickness, left ventricular (LV) posterior wall thickness, systolic and diastolic LV dimensions, and LV ejection fraction were $7.5{\pm}1.0mm$, $7.4{\pm}1.0mm$, $29.9{\pm}2.8mm$, $48.9{\pm}3.6mm$, and $62{\pm}4%$, respectively. LV longitudinal systolic strain (LS) values of apical 4-chamber (A4C) view, apical 3-chamber (A3C) view, apical 2-chamber (A2C) view, and LV global LS (LVGLS) were $-20.1{\pm}2.3$, $-19.9{\pm}2.7$, $-21.2{\pm}2.6$, and $-20.4{\pm}2.2%$, respectively. LV longitudinal systolic strain rate (LVLSR) values of the A4C view, A3C view, A2C view, and LV global LSR (LVGLSR) were $-1.18{\pm}0.18$, $-1.20{\pm}0.21$, $-1.25{\pm}0.21$, and $-1.21{\pm}0.21^{-s}$, respectively. Females had lower LVGLS ($-21.2{\pm}2.2%$ vs. $-19.5{\pm}1.9%$, p < 0.001) and LVGLSR ($-1.25{\pm}0.18^{-s}$ vs. $-1.17{\pm}0.15^{-s}$, p < 0.001) values than males. Conclusion: We measured LV longitudinal strain and strain rate values in the normal Korean population. Since considerable gender differences were observed, normal echocardiographic cutoff values should be differentially applied based on sex.