Clinical Study Of The Mitril Valve-tricuspid Valve Distance Offset And Atrial-to-ventricular Length Ratio Measured By Fetal Echocardiography

Objective To set up the normal range of the mitril valve -tricuspid valve distance (MTD) and atrial-to-ventricular length ratio(AVR) in second and third tremister fetuses and to compare MTD and AVR in normal fetus versus those fetuses with atrioventricular valve malformation and simple tricuspid regurgitation.Methods An apical 4-chamber view was obtained at end diastole in fetuses between 20 and 40 weeks'gestation,427 normal fetuses, 23 fetuses with atrioventricular valve malformation and 34 fetus who had only simple tricuspid regurgitation but cardiac malformation were included.The MTD was measured by placing the calipers parallel to the ventricular septum, and with 1 caliper on the inferior portion of the medial insertion of the mitral valve and a second caliper on the superior portion of the medial insertion of the tricuspid valve. Heart length was measured at the level of interventricular septum by placing the calipers on the epicardium at the apex of the heart and on the endocardium at the top of the atrium. Atrial length was measured by shifting the apex caliper to the crossing point of the ventricular septum and tricuspid valve. Ventricular length was calculated as the difference between the heart length and atrial length. Based on these measurements, the atrial-to-ventricular length ratio (AVR) was calculated. Linear regression curves were generated.The measurements were compared the in normal fetus versus 23 fetus with atrioventricular valve malformation and 34 fetus with simple tricuspid regurgitation.Results The mean MTD in all the normal fetuses is 3.55±1.03mm with a range of 1.22-6.82mm. Regression analysis showed that with each 1-week increase in gestational age, the MTD increased 0.203mm. In normal fetus,the AVR ratio did not change with gestation and the mean AVR ratio was 0.623±0.079 (95% prediction interval 0.455 to 0.79). In control group, the MTD and AVR of Ebstein's malformation who were involved in septal valve (6 of 23) were obviously larger than the upper limit of normal, but the MTD of one fetus with Ebstein's malformation involved in inferior valve was in normal range. The MTD of complete atrioventriculer septal defect(8 of 23) was disappeared,partial endocardial cushing defect(2 of 23) was respectively 0.25mm (30 weeks) and 0.31mm(32 weeks), which is smaller than the lower limit of normal, and the AVR of AVSD was larger than the upper limit of normal with mean AVR 0.901±0.096. The MTD of atrioventricular valve dysplacia(6 of 23) was in the normal range and the AVR was larger than upper limit of normal.But the MTD and AVR of 34 simple tricuspid regurgitation fetuses was in the range.Conclusion The MTD and AVR is useful clinically in the detection of Ebstein's malformation and AVSD, identification of atrioventricular valve dysplacia in second and third tremister fetus, and discrimination the character of tricuspid regurgitation. Incorporation of the MTD and AVR measurement into routine antenatal ultrasonography may substantially improve the ability to diagnose Ebstein's malformation, AVSD and other arioventricular valve hypoplasia antenatally.