Page 19 - The role of advanced echocardiography in patients with ischemic heart disease - Rachid Abou

time to strain curves. The value of global longitudinal strain is displayed in each view. Panel D 1 provides the polar map with the regional values and the global longitudinal strain value calculated
from the 17 segments which is within the normal values.
Abbreviations: ANT, anterior; ANT_SEPT, anteroseptal; APLAX, apical long-axis view; GS, global
strain; INF, inferior; LAT, lateral; POST, posterior; SEPT, septal.
When measuring LV GLS, good image quality is a prerequisite, ideally with a minimum frame rate of 40 frames/second. The LV endocardium is traced manually and the thickness of the region of interest where speckles will be tracked, is adjusted to exclude the papillary muscles and the pericardium. The region of interest is also adjusted to exclude the LV outflow tract and the left atrium. Reliable tracking of all myocardial segments throughout the cardiac cycle should be verified visually, and as a rule of thumb, views should be excluded from analysis if insufficient tracking (indicated by the software) is present in one or more myocardial segments. Current platforms still provide LV GLS as negative values since it measures shortening of the myocardium in the longitudinal direction. Therefore, more negative values of LV GLS denote better LV systolic function. However, current recommendations acknowledge the use of LV GLS in absolute values since it may be easier to understand that lower values of LV GLS represent worse LV systolic function.4The accuracy and reproducibility of the measurement of LV GLS relies on the experience of the observer and the image quality. However, previous study has shown that the intraclass correlation coefficient for the measurement of LV GLS were significantly better than those reported for LVEF, independently of the image quality.5 Teaching interventions consisting of tutorial review of reference cases and group discussions have improved the interobserver variability for visual estimation of LVEF.6 However, similar exercises have not shown such an impact on the measurement of LV GLS and only improved moderately the standard deviation and coefficient of variance of segmental longitudinal strain.5
LV GLS: normal values
In a large meta-analysis, including more than 2500 healthy volunteers (mean age 47±11 years, 51% male), normal values of LV GLS ranged from –15.9% to –22.1% [mean 19.7%; 95% confidence interval: -20.4% to -18.9%].7 Although all were healthy individuals, clinical characteristics (e.g. age, gender, body mass index and blood pressure), as well as vendor-specific software used for longitudinal strain analysis, may explain the variation in LV GLS. LV GLS appears to be more impaired in the elderly, as well as in males.8 Furthermore, LV GLS is also heart-rate dependent, with increased heart rates being associated with reduced LV GLS values in healthy subjects.9 Guidelines do not yet describe threshold values of LV GLS, but suggest that -20% (± 2%) may be considered normal.10
13