What is meant by GLS in echocardiography?

GLS (Global Longitudinal Strain) is an echocardiographic measurement of the displacement of myocardial fibers from a baseline state. It can help identify areas of dysfunction and evaluate the adequacy of cardiac contraction in patients with various clinical conditions such as heart failure, coronary artery disease, or hypertension. GLS provides a comprehensive and quantitative assessment of myocardial wall motion and global systolic function. It is measured by placing two apical 4-chamber views: one during end-diastole and one during end-systole on the same plane to generate speckle tracking imaging (STI). STI measures changes in the myocardium's fiber orientation over time, allowing for quantification of strain directionality, as well as systolic peak strain values per segment. The GLS value obtained reflects an average across all segments within an LV wall layer (septum or lateral/posterior wall), providing a better understanding than manually assessed fractional shortening percentage to detect subclinical global contractile impairment from disease states such as heart failure or hypertensive heart disease.