Calculate deformation parameters Data are extracted to Excel 2010 to calculate: Longitudinal strain and strain rate: Global left ventricular systolic longitudinal strain (GLS) is the mean value of the longitudinal 11 strain of 17 segments in all 3 views from the apex (3 chambers, 4 chambers, 2 chambers), are calculated automatically according to the bull's eye map and have negative values, the unit of measure is (%).