2.3.2. Left-sided echocardiographic assessment:
The LV end-diastolic diameter (LVEDD) was used as indicator of LV
dilation. The LV shortening fraction (LVSF) and the tissue Doppler
imaging (TDI)-derived peak systolic annular velocity at the mitral level
of the LV free wall (Sm) were used to assess LV systolic function. To
assess the diastolic LV function we obtained the mitral peak early (E)
and late (A) diastolic velocity using pulsed wave Doppler of the mitral
valve inflow. Also, TDI-derived early diastolic mitral annulus velocity
(Em) was measured at the lateral part of the mitral annulus. The E/Em
ratio and E/A ratio were calculated as indicators of LV filling
pressures. LV Tei index (LVTX) was used as a measurement of global
(systolic and diastolic) LV function. It was calculated using the
TDI-derived isovolumic contraction (IVC), isovolumic relaxation (IVR)
and ejection time (ET) intervals (measured at the lateral part of the
mitral annulus) as previously described[29]. Cui & Robertson
reported in 2006 that the mean normal value of the LVTX for infants aged
1-12 months is 0.35 (0.09), and that a LVTX less than 0.5 is the upper
limit of normal (2Zscore) [33] . Therefore, a
LVTX> 0.5 was defined as LVMD in this study. Figure
1 and Figure 2 show the main echocardiographic measures used in this
study.
2.4. Reproductibility:
To explore intra-observer and inter-observer agreement, 30
echocardiographic studies were randomly selected and analysed offline.
To estimate the intra-observer agreement, the first observer (RG.M)
remeasured the LVTX, RVTX and LVEI with a 30-days interval blinded to
previous measurements and patient information. To assess the
inter-observer agreement, the means of both observers for each
measurement were compared.