Evaluation Of Left Ventricular Function In Healthy Children By Quantitative Tissue Velocity Imaging

Objective:This study was aimed to establish reference values of mitral valve annulus movement velocity and left ventricular (LV) Tei index in children from 0 to 12 years old by quantitative tissue velocity imaging (QTVI), and eventually explore the features of these values in different ages for the evaluation of LV function.Methods:The subjects of this study consist of 212 healthy children for well-child visits in our hospital from Nov.2009 to Feb.2010. Hight, wight and body surface area were recorded. We divided them into 7 groups:<1 month of age group,1 month-of age group, 6 months-of age group,1 year-of age group,3 years-of age group,6 years-of age group and 9-12 years of age group. VIVID-7 ultrasonoscope (GE,USA) was used to evaluate LV function in healthy children. The mitral valve annulus diameters of end diastolic stage were measured at parasternal long axis view of left ventricle and apical four-chamber view, respectively. Flow velocity of mitral valve was measured at apical four-chamber view and that of aortic valve was measured at apical five-chamber view by pulse wave Doppler (PWD). PWD "a" component was measured from the trailing edge of the PWD mitral flow late diastolic A wave to the leading edge of the subsequent PWD mitral flow early diastolic E wave. The "b" component for the PWD was measured from the leading edge to the trailing edge of the PWD AO tract tracing. The Tei index determined by PWD method was calculated as (a-b/b). Images of 3-5 cardiac cycles at apical four-chamber view by QTVI were saved for later analysis. The peak systolic velocity (Sa), early diastolic velocity(Ea), late diastolic velocity (Aa) of mitral valve annulus in lateral wall and ventricular septum at apical four-chamber view were measured by QTVI. QTVI "a"' component was measured from the starting point of QRS wave in ECG to the leading edge of the subsequent early diastolic mitral valve annular QTVI Ea wave. The "b"'component was measured from the leading edge of the systolic mitral annular QTVI Sa wave to the trailing edge of the Sa wave. The Tei index determined by QTVI method was calculated as (a'-b'/b').The statistical differences of data among different ages were analyzed using the software SPSS.Results:(1) The mitral valve annulus parameters of Sa and Ea at lateral wall and ventricular septum were both lowest in the age group of "<1 month" and increase along with age, and most remarkbaly from the group of "1 month-" and "1 year～". The Ea/Aa increased and the E/Ea decreased along with age, and these changes became most obvious in the group of "1 year～". All the parameteres of the group of "3 year～" were close to those of older children. The mitral valve annulus parameters of Sa, Ea, Aa, Ea/Aa and E/Ea between lateral wall and ventricular septum at apical four-chamber view were significantly different (P<0.05). The Sa, Ea and Ea/Aa of lateral wall were higher than those of ventricular septum, and inversely, the Aa and E/Ea of lateral wall were lower than those of ventricular septum.(2) The LV QTVI-Tei index was highest in the group of "<1 month" and declining along with age. The declining was most obvious in the group of "1 month～" and "3 year～", and the index of the group of "3 year～" was close to that of older children. The QTVI-Tei index of mitral valve annulus in lateral wall and ventricular septum both had high correlations with PW-Tei (r=0.791, r=0.705, respectively and p<0.05). The QTVI-Tei of lateral wall had a high correlation to that of ventricular septum (r=0.815, p<0.05).(3) The mitral valve annulus diameter increased along with age. The E/A of transmitral flow also increased with age, and had a positive correlation with Ea/Aa of lateral wall and ventricular septum (r=0.483, r=0.429, respectively, and p<0.05).(4) The effects of age on the Tei index and QTVI parameter presented the pattern of logarithmic curve. Tei index in children older than 3 years had no correlation with age.Conclusions:(1) The QTVI velocity parameters and Tei index of LV mitral valve annulus in lateral wall and ventricular septum are different among children with different age. Age is a fator which influences LV function of children and should be taken into consideration.(2) The QTVI velocity parameters and Tei index of mitral valve annulus in lateral wall and ventricular septum measured in this study can be used as reference values of different ages.(3) The mitral valve annulus diameter is rising along with age in heathy children. The mitral valve annulus diameter measured in this study can be used as reference values of different ages.