Strain analysis:
We assessed strain parameters by speckle-tracking echocardiography. LV
global longitudinal strain (GLS) was computed from apical four-chamber,
two-chamber, and long-axis views using the 18-segment
model.26 GLS was defined as the peak negative strain
during systole.
LA strain was obtained from LA-focused apical four-chamber 2D views at
frame rates >60 frames per second. The LA border was traced
along the endocardium from one side of the mitral annulus to the other,
and a region of interest was automatically defined, then adjusted
manually as recommended to fit the thickness of the LA
wall.27 The software divided the LA into six segments,
scoring tracking quality with the possibility of manual correction. Zero
strain reference was set at LV end-diastole, defined by the frame prior
to mitral valve closure. LA strain values were computed as the average
of accepted atrial segments averaged over three heart cycles and stated
as LA reservoir strain (LASr), LA conduit strain (LAScd), and LA
contractile strain (LASct).27 SD-TPS was calculated as
the mean value of the time-to-peak strain in the six atrial segments.
SD-TPS was calculated separately in three consecutive loops, and an
average of these values is reported. In addition to crude SD-TPS in ms,
SD-TPS was also corrected by the cycle length and expressed as a
percentage of the cardiac cycle SD-TPS (%) =
(\(\frac{SD-TPS(ms)}{Cycle\ length(ms)}\ X\ 100\)). A higher value of
SD-TPS reflects a higher degree of LA MD (Figure 2).