Figure 4.

ISF-plot with timing markers in a patient before (A) and after (B) CRT. To calculate ISF (in this article between AVO and AVC), all shortening (in blue) and all lengthening strain-rates (in yellow) are summed and integrated over the desired time period. Overlapping areas (light green) indicate simultaneous shortening and stretching between different segments (dyssynergy). A/Note large areas of overlap between AVO and AVC in this patient with LBBB, resulting in a high ISF. B/Immediately after CRT, ISF has decreased (less overlap) because little lengthening occurs during ejection and the amount of shortening (blue area) has increased. This suggests conversion of internal strain into external (global) strain.