• GLS is a simple parameter that expresses longitudinal shortening as a percentage (change in length as a proportion to baseline length).
• GLS is derived from speckle tracking, and analyzed by post-processing of apical images of the LV.
• Different software from different manufacturers derive GLS differently. However, common features involve view selection, defining end-systole, tracing the myocardium, assessing tracking quality, and integration.
• Different aspects of strain can be displayed differently. Waveforms can be used to illustrate contraction delay and temporal dispersion in multiple myocardial segments. Parametric displays can be used to illustrate spatial dispersion through the cardiac cycle.
• Because GLS normally varies with age, sex, and LV loading conditions, defining abnormal GLS is not straightforward. However, in adults and children in general, GLS <16% is abnormal, GLS >18% is normal, and GLS 16% to 18% is borderline. (GLS is expressed as a negative number)
• Common errors in the assessment of GLS include errors in triggering, and errors in the definition of the region of interest (i.e., in accurately tracking the LV myocardium throughout systole).
• GLS could be affected in early phase in case of oncology patients after chemotherapy treatment and in some cases is more sensitive parameter than LVEF. In post-transplant patients GLS is a echo parameter used to rule out rejection.

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