| Object:The purpose of this study is to investigate systolic and diastolic function of left and right ventricle of fetuses with umbilical cord around neck in late pregnancy by velocity vector imaging(VVI), and to analyze longitudinal segmental myocardial performance in the left and right ventricle of fetuses, then to discuss the clinical value of VVI in quantitatively evaluating longitudinal function in fetuses.Methods:1 Study Population: The study group consisted of fetuses with umbilical cord around neck in 35～40 weeks of gestational age, who were diagnosed by fetal system ultrasonography. The fetuses were divided into two groups. Group A, was umbilical artery S/D<3.0, including 20 cases, with average gestational weeks of 36.9±1.4, maternal aged 24 to 36 years old, with an average age of 29.1±3.9. Group B, was umbilical artery S/D≥3.0, including 15 cases, with average gestational weeks of 36.7±1.5, maternal aged 22 to 34 years old, with an average age of 27.2±3.2. The control group consisted of 20 normal fetuses without umbilical cord around neck in 35～40 weeks of gestational age, with average gestational weeks of 36.3±1.5, maternal aged 23 to 35 years old, with an average age of 28.0±3.5. Fifty-five singleton fetuses were examined by fetal system ultrasonography and fetal echocardiography. All fetuses were without congenital malformations and intrauterine growth restriction. All the pregnant women were healthy, without diabetes mellitus, hypertension, cardiovascular disease and other chronic diseases, and without taking non-steroidal anti-inflammatory drugs history.2 Instrument: A set of SIMENS ACUSON Sequoia 512 color Doppler ultrasound instrument with the 4V1C transducer with frequency range of 2.25～4.25MHz was used. The instrument had VVI quantitative analysis software.3 Image Acquisition: All the pregnant women were surgeless. Standard high frame rate digital dynamic four-chamber imaging of three consecutive cardiac cycles of all the fetuses were collected and stored for subsequent off-line analysis.4 Image analysis and parameter measurement: All the two-dimensional four-chamber images were interrogated offline using Syngo US Workplace VVI software. Fetal cardiac cycle was decided on the basis of heart dynamics using the anatomic M-mode. At the end-diastolic, when the border was well visualized and then manually traced the endocardial border. The reference sign was placed at the apex of heart. Velocity vectors were displayed in the two-dimensional plane automatically throughout the cardiac cycles. From the same tracked contour of the endo-cardium, two dimensional strain and strain rate were obstained from the velocity of the displacement along the contour.The left and right ventricular longitudinal walls were divided into 6 segments respectively. Peak systolic longitudinal myocardial velocity (Vs), strain (Ss), strain rate (SRs), and peak diastolic longitudinal myocardial velocity (Vd), strain rate (SRd) were recorded for each segment of left and right ventricle. The average peak systolic velocity, strain, strain rate of left ventricular longitudinal 6 segments was the left ventricular global systolic longitudinal velocity (GLVs), global systolic longitudinal strain (GLSs), global systolic longitudinal strain rate (GLSRs). The average peak diastolic velocity, strain rate of left ventricular longitudinal 6 segments was the left ventricular global diastolic longitudinal velocity (GLVd), global diastolic longitudinal strain rate (GLSRd). Similarly, the average peak systolic velocity, strain, strain rate of right ventricular longitudinal 6 segments was the right ventricular global systolic longitudinal velocity (GLVs), global systolic longitudinal strain (GLSs), global systolic longitudinal strain rate (GLSRs). The average peak diastolic velocity, strain rate of right ventricular longitudinal 6 segments was the right ventricular global diastolic longitudinal velocity (GLVd), global diastolic longitudinal strain rate (GLSRd).Results:1 The longitudinal segmental myocardial performance in the left and right ventricle of fetuses The peak systolic and diastolic velocities were both gradually decreased from the basal segment to the apical segment in the left and right ventricle of all the fetuses (P<0.05), whereas the peak systolic and diastolic strain and strain rate showed no significant difference among all segments in every group (P>0.05).2 The comparison of the left ventricular systolic function parameters in the three groupsThe GLSs and GLSRs in the left ventricle of group B were significantly lower than that the corresponding parameters of group A, and the control group (P<0.05). The GLSs and GLSRs of the left ventricle in group A compared with control group, no significant difference was found (P>0.05). The GLVs of the left ventricle showed no significant difference in the three groups (P>0.05).3 The comparison of the left ventricular diastolic function parameters in the three groupsThe GLSRd in the left ventricle of group B were significantly lower than that the corresponding parameter of group A, and the control group (P<0.05). The GLSRd of the left ventricle in group A compared with control group, no significant difference was found (P>0.05). The GLVd of the left ventricle showed no significant difference in the three groups (P>0.05).4 The comparison of the right ventricular systolic function parameters in the three groupsThe GLSs and GLSRs in the right ventricle of group B were significantly lower than that the corresponding parameters of group A, and the control group (P<0.05). The GLSs and GLSRs of the right ventricle in group A compared with control group, no significant difference was found (P>0.05). The GLVs of the right ventricle showed no significant difference in the three groups (P>0.05).5 The comparison of the right ventricular diastolic function parameters in the three groupsThe GLSRd in the right ventricle of group B were significantly lower than that the corresponding parameter of group A, and the control group (P<0.05). The GLSRd of the right ventricle in group A compared with control group, no significant difference was found (P>0.05). The GLVd of the right ventricle showed no significant difference in the three groups (P>0.05).Conclusions:1 The longitudinal segmental myocardial performance in the left and right ventricle of fetuses: The peak velocities are gradually decreased from the basal segment to the apical segment, whereas the peak strain and strain rate are stable among all segments.2 The GLSs, GLSRs, GLSRd in the left and right ventricle of fetuses with umbilical cord around neck of umbilical artery S/D≥3.0 are significantly lower than that the corresponding parameters of fetuses with umbilical cord around neck of umbilical artery S/D<3.0 and the normal fetuses. This indicates that both systolic and diastolic longitudinal function of left and right ventricle decrease in the fetuses with umbilical cord around neck of umbilical artery S/D≥3.0.3 VVI is a novel technique for assessment of myocardial mechanics and that is independent of the angle of image acquisition and heart rate. As a noninvasive tool for quantitatively and objectively assessing systolic and diastolic longitudinal function in fetuses, it provides another useful modality for evaluating fetal cardiac function.
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