Rsearch On The Changes Of Hemodynamics Of Aortic Isthmus Of Normal Fetus In Middle And Late Pregnancy By Prenatal Ultrasonography

Objective:Prenatal ultrasound was used to obtain peak systolic velocity(PSV),Systolic Nadir(NS)and isthmic systolic Index(ISI)of fetal aortic isthmus and peak systolic velocity of Middle cerebral artery(MCA-S),to analyze the changes of hemodynamics in aortic isthmus and its relationship with the development of fetal cerebral vascular network.Methods:A total of 152 normal fetuses at 23-37 gestation weeks were collected and underwent Doppler ultrasound examination to obtain the waveforms of fetal aortic isthmus(AOI)and cerebral middle artery(MCA)on which peak systolic velocity(PSV)and systolic nadir(NS)of AOI and peak systolic velocity of Middle cerebral artery(MCA-S)were measured on the waveforms.ISI was derived from the ratio NS/PSV.Their relationship with gestational weeks and the relationship between NS and MCA-S were analyzed.Results:The systolic end notch of aortic isthmus occurs at 23 week and deepened gradually as gestational age increased,reaching the baseline at about 30 week when NS is0,ISI is 0,and then reverse.As the gestational weeks increasing,PSV and MCA-S increased,while NS and ISI decreased gradually.The ISI reaches zero at about 30 weeks due to the presence of the end systolic deceleration notch of AOI.The curve equations were established regarding the gestation age as the independent variable X,PSV,NS,ISI and MCA-S as the dependent variable Y respectively.Y=-110.982+10.975X-0.242X~2,R~2=0.971,p<0.001;Y=-20.077+5.84X-0.073X~2,R~2=0.794,p<0.001;Y=-0.705+0.087X-0.002X~2,R~2=0.97,p<0.001;Y=-67.291+4.841X-0.036X~2,R~2=0.911,p<0.001;Establish a curve equation rega^rding MCA-S as the independent variable X,NS as the dependent variable Y respectively.Y=12.757+0.58X-0.02X~2,R~2=0.854,p<0.001。Conclusions:With the gestational age increases,PSV of fetal aortic isthmus and MCA-S increase,aortic isthmic NS and ISI decrease,while NS decreases with the increase of MCA-S,indicating that when the gestational age increases,the systolic end notch of aortic isthmus gradually deepened,and which is related to the development of fetal cerebral vascular network in the second and third trimester.