Fetal abdominal blood vessels and organ microvasculature detected by Slowflow HD

Slow flow HD and traditional CDFI technologies in identifying pulmonary veins in the first trimester

OBJECTIVE

This study aims to assess the feasibility and effectiveness of color doppler flow imaging (CDFI) technology and the Slow Flow HD imaging technique in identifying fetal pulmonary veins (PVs) in the first trimester (11-13 + 6 weeks), and further explore the factors affecting fetal pulmonary vein identification in early pregnancy.

METHODS

Echocardiography and scanning of PVs were performed in 240 normal singleton fetuses in early pregnancy by using CDFI and slow flow HD techniques, to compare the ability of two methods to identify the PVs. Slow Flow HD technology was used to further investigate the difference of PVs identification at different gestational ages [group I (11-11 + 6 weeks), group II (12-12 + 6 weeks), group III (13-13 + 6 weeks)] and with different maternal body mass indices (BMI) (≥ 25 and < 25). In 31 cases of 240 fetuses, transvaginal ultrasonography was added due to maternal habitus or significant retroversion of the uterus, and the difference in PVs identification between transabdominal and transvaginal examination was analyzed.

RESULTS

Successful PVs identification rates via CDFI and Slow Flow HD were 32.0% and 88.3%, respectively (p < 0.05). The identification rate of at least one and two pulmonary veins in Slow Flow HD was 88.3% and 76.2%, and all four pulmonary veins in 11.6% (p < 0.05). The identification rate of group I, II and III were 76.4%, 88.9% and 96.0%, respectively. The identification rate was 45.1% in the transabdominal ultrasound group and 83.8% in the transvaginal ultrasound group. The identification rate was 62.5% in the BMI ≥ 25 group and 94.7% in the BMI < 25 group (p < 0.05).

CONCLUSIONS

Slow Flow HD can detect PVs in early pregnancy more often than using CDFI. Slow Flow HD is a feasible and effective imaging technique for evaluating PVs in early pregnancy.

Prenatal assessment of pulmonary vasculature development in fetuses with congenital diaphragmatic hernia: A literature review

Pathophysiological studies have shown that pulmonary vascular development is impaired in fetuses with a congenital diaphragmatic hernia (CDH), leading to a simplified vascular tree and increased vascular resistance. Multiple studies have described prenatal ultrasound parameters for the assessment of the pulmonary vasculature, but none of these parameters are used in daily clinical practice. We provide a comprehensive review of the literature published between January 1990 and February 2022 describing these parameters, and aim to explain the clinical relevance of these parameters from what is known from pathophysiological studies. Prenatal detection of a smaller diameter of the contralateral (i.e. contralateral to the diaphragmatic defect) first branch of the pulmonary artery (PA), higher pulsatility indices (PI), higher peak early diastolic reverse flow values, and a lower vascularization index seem of added value for the prediction of survival and, to a lesser extent, morbidity. Integration within the routine evaluation is complicated by the lack of uniformity of the methods used. To address the main components of the pathophysiological changes, we recommend future prenatal studies in CDH with a focus on PI values, PA diameters and pulmonary vascular branching.

Natural Course of Fetal Hyaloid Artery: SlowflowHD Longitudinal Study

OBJECTIVE

To assess the natural course of the fetal hyaloid artery (FHA) using SlowflowHD during pregnancy.

METHODS

One-hundred and eighteen normal fetuses were studied longitudinally using SlowflowHD to assess the natural course of FHA at 18-21 + 6, 28-31 + 6, and after 35 weeks of gestation. Blood flow of FHA with/without its branches (BF) was evaluated using SlowflowHD, and the band of FHA without blood flow (Band) was identified in each gestational period. The natural course of FHA was classified into six types: Type A, not detected (ND) in each gestational period; Type B, Band at 18-21 + 6 weeks; Type C, Band at 18-21 + 6 and 28-31 + 6 weeks; Type D, BF at 18-21 + 6 weeks; Type E, BF at 18-21 + 6 weeks and Band at 28-31 + 6 weeks; Type F, BF at 18-21 + 6 and 28-31 + 6 weeks.

RESULTS

BF, Band, and ND were 83.5, 15.5, and 1.0% at 18-21 + 6 weeks, 8.8, 15.5, and 75.7% at 28-31 + 6 weeks, and 0, 0, and 100% after 35 weeks, respectively. Type A was 1.0%, Type B was 13.6%, Type C was 1.9%, Type D was 61.2%, Type E was 13.6%, and Type F was 8.7%.

CONCLUSIONS

The presence of FHA blood flow before 30 weeks of gestation should be regarded as a physiologic phenomenon in normal fetuses.

Function and Safety of SlowflowHD Ultrasound Doppler in Obstetrics

SlowflowHD is a new ultrasound Doppler imaging technology that allows visualization of flow within small blood vessels. In this mode, a proprietary algorithm differentiates between low-speed flow and signals attributed to tissue motion so that microvessel vasculature can be examined. Our objectives were to describe the low-velocity Doppler mode principles, to assess the bone thermal index (TIb) safety parameter in obstetric ultrasound scans and to evaluate adherence to professional guidelines. To achieve the latter goals, we retrospectively reviewed prospectively collected ultrasound images and video clips from pregnancy ultrasound scans at >10 wk of gestation over 4 mo. We used a custom-built optical character recognition-based software to automatically identify all images and video clips using this technology and extract the TIb. Overall, a total of 185 ultrasound scans performed by three fetal medicine physicians were included, of which 60, 54 and 71 scans were first-, second- and third-trimester scans, respectively. The mean (highest recorded) TIb values were 0.32 (0.70), 0.23 (0.70) and 0.32 (0.60) in the first, second, and third trimesters, respectively. Thermal index values were within recommended values set by the World Federation for Ultrasound in Medicine and Biology American Institute of Ultrasound in Medicine and British Medical Ultrasound Society in all scans.

Assessment of uterine receptivity by endometrial and sub-endometrial blood flow using SlowflowHD in hormone prepared frozen embryo transfer cycles: a pilot study

PURPOSE

Utilizing SlowflowHD as a measurement of endometrial and sub-endometrial blood flow in women with infertility undergoing frozen embryo transfer (FET) cycles and correlation with pregnancy outcomes.

METHODS

A prospective pilot study of 99 women undergoing hormone replacement FET cycles. Ultrasounds were performed with Voluson E8 at 3-time points: day 15, day of transfer, and 11 days post transfer (T + 11). SlowflowHD Doppler blood flow indices in the endometrium and sub-endometrium were compared in women who achieved pregnancy with those who did not.

RESULTS

Using SlowflowHD, both pregnant and non-pregnant women had similar trends with decreased endometrial blood flow day of transfer compared with day 15. However, there was a borderline significantly lower mean percentage decrease of endometrial blood flow in women achieving a pregnancy (28.3% vs 42.9%). Significantly higher numbers of pregnant women had a 20% or less decrease in blood flow (21 vs 9) with increases in mean percentage blood flow on T + 11 (pregnant 39.59% vs non-pregnant 25.20%). The RI and S/D ratio in the spiral arteries was also significantly higher on transfer day in women who had a live birth RI (0.68 vs 0.65) and S/D (3.91 vs 3.17).

CONCLUSION

There are blood flow changes both in pregnant and non-pregnant patients with decreases in blood flow after progesterone replacement. Pregnancy and live births were associated with a lower mean percentage drop in blood flow from day 15 to the day of transfer and elevated RI and S/D ratio on transfer day.

Detection and significance of main anchoring villus in early pregnancy

OBJECTIVE

To find and explore the relationship among the length of the embryo's main anchoring villus and the week of gestation, embryonic crown-rump length (CRL), and maternal blood human chorionic gonadotropin (hCG) during early pregnancy using ultrasound.

METHODS

A total of 108 women with singleton pregnancies underwent ultrasound examination of the fetus during the early months of their pregnancy (5⁺⁵ -13⁺⁶  weeks of pregnancy). The main anchoring villus was detected using HD-Flow and SlowflowHD mode ultrasound. The detection rate and length of the main anchoring villus were recorded. The correlations among main anchoring villus with gestational weeks, CRL, and blood hCG were obtained.

RESULTS

The main anchoring villus was detected in all women (108/108). It could be found throughout the early gestational weeks from as early as 4⁺⁶  weeks. The length of the main anchoring villus increased with gestational age, and was positively correlated with CRL and the logarithm of hCG (P < 0.05).

CONCLUSION

Our results showed that the detection rate of the main anchoring villus was 100% and the length of the main anchoring villus was correlated with gestational week, CRL, and blood hCG. The main anchoring villus could represent where the embryo implanted.