Blood flow occlusion via ultrasound image-guided high-intensity focused ultrasound and its effect on tissue perfusion

This study investigated the induction of tissue necrosis by arterial blood flow occlusion using ultrasound image-guided high-intensity focused ultrasound (HIFU). We constructed a prototype HIFU transducer in combination with an imaging probe that provided color Doppler imaging and ultrasound contrast imaging. The HIFU beam was aimed into a branch of the renal artery in vivo. The renal artery branches of eight rabbits were occluded by HIFU at an intensity of 4 kW/cm(2) (from 2 to 10 times of each sonication for 5 s). When the HIFU exposure was successful, complete cessation of blood flow was observed by color Doppler imaging with success rate of 100% (8/8). Furthermore, lack of perfusion was observed in the renal cortex with a contrast-enhanced image. Postmortem histologic evaluation showed a wedge-shaped area of infarction in six of seven cases, corresponding to the lack of the contrast medium in the ultrasound image. These results demonstrated that ultrasound image-guided HIFU can be used to induce arterial occlusion, thus producing infarction and necrosis of the perfused tissue.     

Functional and histological changes in rat femoral arteries by HIFU exposure

This study was an investigation of arterial contractility in response to high-intensity focused ultrasound (HIFU) and of histologic changes to the artery with various intensities of HIFU. We constructed a prototype HIFU transducer in combination with an imaging probe that provides color Doppler imaging and Doppler velocimetry. HIFU was applied through the skin to deep femoral arteries in left thighs of Sprague-Dawley rats; color images of the blood flow were used to aim the HIFU beam. Peak intensities used were 530, 1080, 2750 and 4300 W/cm2. The duration of each HIFU exposure was 5 s. HIFU was applied to five focal spots of each leg. These focal spots were aligned with a spacing of 1.0 mm so as to form a line across the artery. Blood flow occlusion was accomplished by HIFU at an intensity of 4300 W/cm2, but the flow continued with the lower intensities. Peak systolic velocities (PSVs) of blood flow as measured by Doppler velocimetry increased in the arteries to which HIFU had been applied at 1080 and 2750 W/cm2. The increase corresponded with HIFU intensity. Exposure to HIFU at 530 W/cm2 did not change the blood flow velocity. Histologic studies have demonstrated that exposure to HIFU at 2750 and 4300 W/cm2 leads to vacuolar degeneration and destruction of elastic fibers of the tunica media of the artery. Exposure at 1080 W/cm2 led to increased PSV, but did not induce histologic changes in the vessel wall. In conclusion, the response of the artery to HIFU varied with intensity. Vascular contraction without tissue degeneration occurred at low intensity; with increasing intensity, the tissue degeneration detectable in histology reduced the vascular diameter and, finally, at high intensity, the blood flow was occluded. Although these phenomena appeared to be mainly due to thermal effects, mechanical effects might have some role, particularly on vascular contraction.     

High-intensity focused ultrasound treatment for twin reversed arterial perfusion sequence

Twin reversed arterial perfusion (TRAP) sequence is a serious complication of monochorionic twin pregnancies, in which arterioarterial anastomoses allow blood flow from a 'pump' fetus to an acardiac fetus via reversed flow in the latter's umbilical artery. Several trial treatments for TRAP sequence have been reported, but all of these have been invasive. We present a case of TRAP sequence in which high-intensity focused ultrasound (HIFU) was applied to the umbilical artery of the anomalous twin at 26 weeks as a non-invasive fetal therapy. The HIFU intensity was set at approximately 2300 W/cm(2) with exposure periods of 10 s. Color Doppler ultrasound showed a decrease in blood supply to the anomalous twin, although complete occlusion of the targeted vessel was not achieved. Delivery was by Cesarean section at 29 weeks' gestation and the pump twin survived, without severe clinical complications at 6 months. Copyright ? 2012 ISUOG. Published by John Wiley & Sons, Ltd.     

Antenatal umbilical coiling index and Doppler flow characteristics.

OBJECTIVE: To evaluate whether a relationship exists between the antenatal umbilical coiling index (UCI) and umbilical cord Doppler flow characteristics. METHODS: During the fetal anatomical survey in 200 consecutive pregnant patients at 18-23 weeks' gestation, we recorded umbilical coiling patterns and blood flow characteristics. The antenatal UCI, calculated as a reciprocal value of the distance between a pair of umbilical cord coils, was compared with Doppler parameters including umbilical vein blood flow volume (in mL/min/kg), and mean resistance index (RI) and peak systolic velocity (PSV in cm/s) averaged from both umbilical arteries. RESULTS: A total of 154 patients met the inclusion criteria of singleton pregnancy and having adequate sonographic umbilical cord images, Doppler flow indices, and all demographic, antenatal and labor data. The mean antenatal UCI was 0.40, with 10th and 90th centiles of 0.20 and 0.60, respectively. The mean +/- SD umbilical artery RI and PSV and umbilical vein blood flow volume were 0.74 +/- 0.07, 25.1 +/- 6.4 cm/s, and 264 +/- 106 mL/min/kg, respectively. All Doppler variables correlated significantly with antenatal UCI, with lower RI and higher PSV and umbilical vein blood flow volume values being associated with higher antenatal UCI (P = 0.016, P < 0.001, and P = 0.032, respectively). However, when stratified by antenatal UCI into hyper- (above 90th centile), normo- (10th-90th centile), and hypocoiled (below 10th centile) umbilical cord groups, a significant difference was observed for PSV only (P = 0.016). CONCLUSION: It appears that umbilical cord coiling modulates noticeably blood flow through the umbilical cord. We speculate that more prominent umbilical coiling (higher antenatal UCI values) has a protective effect on blood flow in terms of decreased arterial resistance and higher blood flow velocities, as well as increased venous blood flow. However, due to lack of significant differences between Doppler characteristics when stratified by antenatal UCI into hypo-, normo-, and hypercoiled groups, the clinical implications of this observation are uncertain.     

Pulsatile flow phantom for ultrasound image-guided HIFU treatment of vascular injuries

A pulsatile flow phantom was developed for studies of ultrasound image-guided high intensity focused ultrasound (HIFU) application in transcutaneous hemostasis of injured blood vessels. The flow phantom consisted of a pulsatile pump system with instrumented excised porcine carotid artery, which was imbedded in a transparent agarose gel to model structural configuration of in vivo tissues. Heparinized porcine blood was circulated through the phantom. The artery was injured using an 18-gauge needle to model a penetrating injury in human peripheral vasculature. A HIFU transducer with the diameter of 7 cm, focal length of 6.3 cm and frequency of 3.4 MHz was used to seal the puncture. Ultrasound imaging was used to localize and target the puncture site and to monitor the HIFU treatment. Triphasic blood flows present in the human arteries were reproduced, with flow rates of 50 to 500 mL/min, pulse rates of 62 to 138 beats/min and peak pressures of 100 to 250 mm Hg. The penetrating injury of an artery was mimicked successfully in the flow phantom setting and was easily visualized both optically through the transparent gel and with power Doppler ultrasound imaging. Hemostasis was achieved in 55 +/- 31 s (n = 9) of HIFU application. Histologic observations showed that a HIFU-sealed puncture was filled with clotted blood and covered with a fibrin cap. The pulsatile flow phantom provides a controlled and repeatable environment for studies of transcutaneous image-guided HIFU application in hemostasis of a variety of blood vessel injuries.     

Assessment of umbilical arterial and venous flow using color Doppler.

OBJECTIVE: To estimate the umbilical artery and vein blood volume flow using B-mode and Doppler ultrasound in the second and third trimesters of pregnancy. DESIGN: This was a cross-sectional study of 129 singleton, healthy pregnancies at 23-33 weeks' gestation. The umbilical artery and vein cross-sectional area, time-averaged velocity and pulsatility index were measured in a free loop of cord, and the fetal weight was estimated. Ranges for each parameter were obtained; from these the blood flow for the vein and artery was calculated, and the average flow corrected for fetal weight was derived. RESULTS: The median time for examination was 6 min. The mean cross-sectional area and time-averaged velocity for both the vein and artery increased linearly with gestation. The umbilical artery flow correlated closely with the average vein flow (r = 0.9, p < 0.001). There was a significant, though poor, inverse correlation between the umbilical artery pulsatility index and the average umbilical flow (r = -0.25, p < 0.05). The average umbilical flow (calculated from the mean of arterial and venous flow), corrected for estimated fetal weight, decreased from 189.2 ml/kg per min at 23 weeks to 176.2 ml/kg per min at 33 weeks' gestation. CONCLUSION: The estimates of fetal umbilical flow obtained by this Doppler method are consistent with previously published data. Averaging the arterial and venous flow is theoretically advantageous in reducing the inherent errors in estimating either the arterial or the venous flow. This method of measuring umbilical flow may have clinical potential in assessing fetal health and disease processes.     

Application of high-intensity focused ultrasound for fetal therapy: experimental study using an animal model of lower urinary tract obstruction

Objective

The purpose of this study is to investigate whether high-intensity focused ultrasound (HIFU) exposure is able to produce a fistula between the bladder and abdominal wall of a fetus with lower urinary tract obstruction (LUTO).

Materials and methods

We constructed a prototype HIFU transducer in combination with an imaging probe. HIFU was applied to the lower abdomen of a rabbit neonate that was complicated by LUTO as an experimental model to produce a fistula; HIFU was applied in a tank filled with degassed water. Exposed lesions were assessed by histological analysis at necropsy.

Results

When HIFU was applied at 5.5 kW/cm² of spatial-peak temporal average intensity (SPTA), a fistula was created between the lower abdominal wall and the urinary bladder; urine gushed out from the bladder through the fistula within 60 s after HIFU exposure.

Conclusion

The findings suggest that fetal diseases such as LUTO can be non-invasively treated using HIFU exposure from even outside the maternal body, though this study was performed in a water tank.     

Fetal brain/liver volume ratio and umbilical volume flow parameters relative to normal and abnormal human development.

OBJECTIVES: To estimate fetal brain volume from head circumference and published postmortem data; to determine normal values for the fetal brain/liver volume ratio relative to gestational age; to establish the relationship between the brain/liver volume ratio and fetal circulatory parameters during normal and restricted (SGA) fetal growth. PATIENTS AND METHOD: This was a cross-sectional study involving a total of 47 uncomplicated pregnancies appropriate-for-gestational age (AGA) and 23 pregnancies resulting in the delivery of a SGA fetus. At enrollment gestational age ranged between 20 and 36 weeks in both groups. Umbilical venous cross-sectional area and time-averaged velocity for calculation of volume flow as well as velocity waveforms from the umbilical artery, middle cerebral artery and ductus venosus, were recorded. Fetal liver volume measurements were obtained using three-dimensional ultrasound. Fetal brain volume was estimated from fetal head volume following comparison with published postmortem data on fetal brain weight. RESULTS: A significant correlation was observed between prenatally estimated fetal head volume and postmortem fetal brain volume. Fetal brain volume was approximately half that of fetal head volume. The normal fetal brain/liver volume ratio demonstrated a significant reduction with gestational age (R = -0.54; P < 0.001). The normal mean +/- standard deviation (SD) fetal brain/liver volume ratio (3.4 +/- 0.7) was significantly different (P < 0.001) from the mean fetal brain/liver volume ratio in the SGA group (n = 23) (5.9 +/- 1.9). A significant difference existed for mean umbilical venous volume flow between AGA (104.7 +/- 26.9 mL/min/kg) and SGA (59.6 +/- 22.7 mL/min/kg) fetuses. In the SGA fetus, there was a significant inverse relationship (P < 0.001) between fetal weight-related umbilical venous volume flow and fetal brain/liver volume ratio. In a subset of 16 SGA and 16 AGA fetuses matched for gestational age, a significant difference existed for umbilical artery pulsatility index (2.30 +/- 1.52 vs. 0.99 +/- 0.19), fetal middle cerebral artery pulsatility index (1.3 +/- 0.4 vs. 2.1 +/- 0.3) and late diastolic flow velocity in the fetal ductus venosus (6.9 +/- 14.2 cm/s vs. 23.9 +/- 8.8 cm/s), but not for peak systolic, early diastolic and time-averaged velocity in the ductus venosus. CONCLUSION: Sonographic estimates of fetal brain volume can be obtained. The fetal brain/liver volume ratio is a predictor of fetal outcome in the growth-restricted fetus. An inverse relationship exists in SGA fetuses between brain/liver volume ratio and fetal weight-related umbilical venous blood flow.     

Relationship between umbilical and fetal cerebral blood flow velocity waveforms and umbilical venous blood gases.

Nineteen women (mean +/- SD: 28 +/- 5 years) with small fetuses relative to gestational age (mean +/- SD: 32 +/- 2.2 weeks of gestation) were referred to our unit for cordocentesis for the determination of fetal karyotyping. Four of these 19 patients had small-for-gestational-age ultrasound-derived measurements under the third centile for gestational age. Fetal blood gases were measured in the umbilical vein. Umbilical artery and fetal internal carotid artery Doppler examinations were performed 15 min before cordocentesis. The results showed a progressive and proportional increase in umbilical artery resistance index with hypoxia (p < 0.001), hypercapnia (p < 0.025) and acidosis (p < 0.005). Moreover, the results showed a progressive and proportional decrease in fetal internal carotid artery resistance index with hypoxia (p < 0.01), hypercapnia (p < 0.01) and acidosis (p < 0.025). Fetal blood gases are therefore related to umbilical circulatory function and cerebral vasodilatation, suggesting fetal vascular redistribution.     

Doppler ultrasound measurements in the central circulation of anesthetized fetal sheep during obstruction of umbilical-placental blood flow.

OBJECTIVE: To establish by Doppler ultrasound the effects of acute blockage of umbilical cord vessels on the fetal central circulation. DESIGN: Experimental study in anesthetized pregnant sheep. METHODS: In 11 anesthetized pregnant sheep (0.66 of gestation), Doppler velocity profiles and/or venous flow rates were recorded in the ductus venosus, the fetal aorta, the umbilical arteries and the umbilical vein. This involved three phases. In Phase 1, the abdominal wall was closed (n = 9); Phase 2 was during fetoscopy after laparotomy (n = 8); Phase 3 was after coagulation of one of the umbilical arteries (n = 10). As an additional intervention in six fetuses, the umbilical cord was clamped for 5-15 s while blood flow velocity changes in the ductus venosus were observed. RESULTS: There were no significant differences between Doppler recordings in Phases 1 and 2. During Phase 3, the pulsatility index of the aorta and of the coagulated umbilical artery increased significantly. The umbilical vein blood flow rate was significantly reduced from a median of 408 (range, 243-575) mL/min/kg in Phase 1 to a median of 173 (range, 107-426) mL/min/kg in Phase 3, but the blood flow rate in the ductus venosus (median, 94; range, 56-148 mL/min/kg vs. median, 92; range, 33-237 mL/min/kg) remained unchanged. The ductus venosus/umbilical vein ratio increased from a median of 0.22 (range, 0.13-0.41) to 0.56 (range, 0.17-0.97) (P < 0.05). Compression of the cord (5-15 s) immediately reduced the time averaged maximum velocity in the ductus venosus from a mean of 51 (standard deviation, 11) cm/s to 20 (standard deviation, 6) cm/s (P < 0.001) without significant changes of the velocity profile. However, the pulsatility index increased from a mean of 0.55 (standard deviation, 0.19) to 1.89 (standard deviation, 0.73) (P < 0.001). CONCLUSION: Central venous flows in anesthetized fetal sheep are unaffected by laparotomy and hysterotomy. Obliteration of one umbilical artery increases the ductus venosus/umbilical vein volume flow (mL/min/kg) ratio. Compression of the umbilical cord shifts down blood flow velocity profiles in the ductus venosus, and the pulsatility index thus increases.     

Assessment of transmural coronary blood flow with intraoperative transesophageal color Doppler echocardiography during coronary revascularization.

Intraoperative color Doppler transesophageal echocardiography with a 4- to 7-MHz transducer was performed on 28 consecutive patients who underwent coronary artery bypass grafting to image and evaluate the transmural coronary blood flow before and after cardiopulmonary bypass. The transmural coronary flow was visualized in 26 (92.8%) of 28 patients in the inferior wall and in 13 (46.4%) of 28 patients in the lateral wall. The peak diastolic flow velocity of the transmural coronary artery in the inferior and lateral wall was significantly increased after coronary revascularization in patients with a successful bypass graft to the right coronary artery (from 34.0 +/- 19.7 to 64.9 +/- 30.9 cm/s, P <.001, n = 10) and to the left circumflex coronary artery (from 35.1 +/- 18.6 to 62.1 +/- 21.1 cm/s, P <.001, n = 10). No significant changes were observed in patients with no bypass graft to the right or left circumflex coronary artery. Coronary blood flow can be mapped and the velocity measured with Doppler transesophageal echocardiography with a high-frequency (4- to 7-MHz) transducer. Assessment of the transmural coronary flow may provide valuable information and aid in decision making during surgical revascularization.     

Fetal cerebral blood flow redistribution in late gestation: identification of compromise in small fetuses with normal umbilical artery Doppler.

OBJECTIVE: To evaluate the role of middle cerebral artery Doppler in small fetuses during the late third trimester. DESIGN: Prospective observational study of structurally normal fetuses with an estimated fetal weight < 5th percentile for gestation. Perinatal outcome was determined using a structured datasheet sent to each referring obstetrician. SUBJECTS: Structurally normal fetuses at 35 or more weeks of gestation referred during a 2-year period to the fetal growth clinic of a regional fetal medicine unit in North London. Fetuses with aneuploidy and/or major structural abnormalities were excluded. METHODS: Umbilical artery and middle cerebral artery (MCA) Doppler waveforms were recorded and considered abnormal if above 95th or below 5th percentiles, respectively. Amniotic fluid was considered reduced if the maximum vertical cord-free pool was < 2 cm. The placenta was considered mature if the Grannum grade was II or III. The head circumference (HC)/abdominal circumference (AC) ratio was considered abnormal if > 95th percentile for gestation. Fetal growth, amniotic fluid, biophysical profile score and umbilical artery Doppler were used to advise the referring obstetrician about fetal well-being and he/she independently decided both the timing and mode of delivery. RESULTS: Forty-seven fetuses fulfilled the entry criteria. Thirty-four (72%) demonstrated normal umbilical artery Doppler waveforms. Sixteen (34%) demonstrated middle cerebral artery redistribution, of which nine (56%) had normal umbilical artery Doppler waveforms. MCA blood flow redistribution was associated with an increased incidence of cesarean delivery and need for neonatal admission. Of all gray-scale parameters, an elevated HC/AC ratio has the strongest association with MCA blood flow redistribution (15/16 vs. 1/31; P < 0.01). CONCLUSIONS: MCA Doppler may be a useful tool to assess the health of small fetuses in the late third trimester. Redistribution may occur in the presence of normal umbilical artery Doppler and should be suspected when the HC/AC ratio is elevated.     

Basic study of less invasive high-intensity focused ultrasound (HIFU) in fetal therapy for twin reversed arterial perfusion (TRAP) sequence

Purpose

The objective of the present study was to develop a high-intensity focused ultrasound (HIFU) transducer more suitable for clinical use in fetal therapy for twin reversed arterial perfusion (TRAP) sequence.

Materials and methods

We created a cooling and degassed water-circulating-type HIFU treatment device. HIFU was applied to renal branch vessels in three rabbits. Sequential HIFU irradiation contains a trigger wave, heating wave, and rest time. The duration of HIFU application was 10 s/course. Targeting could be achieved by setting the imaging probe in the center and placing the HIFU beam and imaging ultrasonic wave on the same axis.

Result

We confirmed under sequential HIFU irradiation with a total intensity of 1.94 kW/cm² (spatial average temporal average intensity) that the vein and artery were occluded in all three rabbits.

Conclusion

Simultaneous occluding of the veins and arteries was confirmed with trigger waves and a resting phase using the HIFU transducer treatment device created for this study. Clinical application appears possible and may represent a promising option for fetal therapy involving TRAP sequence.

     

Umbilical vein blood flow in fetuses with normal and lean umbilical cord.

OBJECTIVE: To evaluate whether umbilical vascular coiling is correlated with the umbilical vein blood flow profile and to investigate if this is different between fetuses with a lean and those with a normal umbilical cord. METHODS: Consecutive women with a singleton gestation who delivered at term and who underwent an ultrasound examination within 24 h from delivery were studied. Umbilical cord and vessel areas were calculated. Umbilical vein blood flow parameters were obtained by digital color Doppler velocity profile integration. After delivery, the umbilical coiling index was calculated. RESULTS: One hundred and sixteen women were studied. Twelve (10.3%) had a lean umbilical cord (area < 10th centile). A significant correlation was found between the umbilical coiling index and the umbilical vein blood flow (r = 0.67, P < 0.001). A significant difference between fetuses with and without a lean cord was found in terms of: umbilical coiling index (0.18 +/- 0.08 vs. 0.29 +/- 0.09, P < 0.005), cord area (87.6 +/- 5.1 mm2 vs. 200.6 +/- 34.6 mm2, P < 0.001), Wharton's jelly amount (25.7 +/- 10.3 mm2 vs. 122.1 +/- 33.4 mm2, P < 0.001), umbilical vein blood flow (93.7 +/- 17.8 ml/kg per min vs. 126.0 +/- 23.4 ml/kg per min, P < 0.001), and umbilical vein blood flow mean velocity (6.6 +/- 2.7 cm/s vs. 9.0 +/- 3.6 cm/s, P < 0.05). The proportion of fetuses with an umbilical vein blood flow < 80 ml/kg per min was higher when the cord was lean than when it was normal (25% vs. 1.9%, P < 0.01). CONCLUSIONS: Lean umbilical cords differ from normal cords not only from a structural point of view but also in the umbilical vein blood flow characteristics. This could explain the increased incidence of intrapartum complications and fetal growth restriction among fetuses with a lean and/or hypocoiled cord.     

Relationship between arterial and venous Doppler and perinatal outcome in fetal growth restriction.

OBJECTIVE: The aim of this investigation was to assess the relationship between abnormal arterial and venous Doppler findings and perinatal outcome in fetuses with intrauterine growth restriction (IUGR). METHODS: Doppler velocimetry of the umbilical artery (UA), middle cerebral artery (MCA), inferior vena cava (IVC), ductus venosus (DV) and free umbilical vein was performed in 121 IUGR fetuses with a UA pulsatility index (PI) > 2 SD above the gestational age mean and subsequent birth weight < 10th centile for gestational age. Groups based on the last Doppler exam were: 1 = abnormal UA-PI only (n = 42, 34.7%), 2 = MCA-PI > 2 SD below the gestational age mean (= 'brain sparing') in addition to abnormal UA-PI (n = 29, 24.0%), 3 = DV or IVC peak velocity index (PVIV) > 2 SD above the gestational age mean and/or pulsatile UV flow (n = 50, 41.3%). Z-scores (delta indices) were calculated for Doppler indices. Perinatal mortality, respiratory distress (RDS), bronchopulmonary dysplasia (BPD), intraventricular hemorrhage (IVH), necrotizing enterocolitis (NEC), circulatory failure and umbilical artery blood gases were recorded. RESULTS: Absence or reversal of umbilical artery end-diastolic flow was observed in 4 (9.5%) of fetuses in group 1, 10 (34.5%) fetuses in group 2 and 41 (82%) fetuses in group 3. A low middle cerebral artery pulsatility index was found in 39 (78%) fetuses in group 3. Multiple regression analysis with gestational age at delivery, delta indices and cord artery blood gas as independent parameters and individual perinatal outcomes as dependent variables was performed. In this analysis the association was strongest with gestational age for each complication. There were no significant differences in Apgar scores between groups. At delivery, 'brain sparing' was associated with hypoxemia and abnormal venous flows with acidemia. Perinatal mortality was highest in group 3 and stillbirth was only observed when venous flow was abnormal. All postpartum complications were more frequent in fetuses with abnormal venous flows. The only statistically significant relation between Doppler indices and outcome was the association between abnormal ductus venosus flow and fetal death (r2 = 0.24, P < 0.05). CONCLUSION: Growth restricted fetuses with abnormal venous flow have worse perinatal outcome compared to those where flow abnormality is confined to the umbilical or middle cerebral artery. In fetuses with low middle cerebral artery pulsatility, venous Doppler allows detection of further deterioration. While abnormal venous flows can be significantly associated with fetal demise, gestational age at delivery significantly impacts on all short-term outcomes.     

彩色多谱勒对IUGR脐动脉血流的检测

目的：应用彩色多谱勒检测正常妊娠和胎儿宫内发育迟缓（以简称ＩＵＧＲ）的脐动脉血流指标ＰＩ、ＲＩ、Ｓ／Ｄ值。材料和方法：应用彩色多谱勒检测了２００例正常妊娠和１１１例ＩＵＧＲ的脐动脉血流,孕周从２６－４１周。结果：正常妊娠组及ＩＵＧＲ组的脐动脉血流指标均随妊娠周数的增高而降低,但ＩＵＧＲ组的脐动脉血流ＰＩ、ＲＩ、Ｓ／Ｄ值明显高于正常妊娠组（Ｐ〈０．０１）。孕３０周后,脐动脉血流Ｓ／Ｄ值〉４,揭示胎儿预后不良。结论：脐动脉血流检测不仅是胎儿监护的一种方法,而且可作为诊断ＩＵＧＲ的一个指标及对估计胎儿预后有一定的临床价值。     

Selective reduction of multifetal pregnancy using high-intensity focused ultrasound in the rabbit model.

OBJECTIVE: High-order multifetal pregnancies carry a significant risk of obstetric complications and poor pregnancy outcome. Selective reduction has traditionally been performed using transabdominal and transvaginal ultrasound-guided intracardiac injection of potassium chloride. We have previously shown that high-intensity focused ultrasound (HIFU) can create a coagulative tissue necrosis in the sheep fetus. The objective of this study was to investigate the feasibility of non-invasive selective fetal reduction using HIFU in a rabbit model. METHODS: A protocol for HIFU-induced tissue coagulation was developed in the rabbit model. The fetal heart was targeted with ultrasound-guided tissue ablation by a HIFU beam. Five time-mated does between 20-29 days' gestation underwent transabdominal fetal cardiac ablation in a total of 11 fetuses. The HIFU system consisted of a 7-MHz high-power transducer, operated at 2000 W/cm2. The fetal heart rate was observed using real-time ultrasound with Doppler flow velocimetry. All lesions were assessed macroscopically and by histological analysis. RESULTS: Severe bradycardia leading to asystole was observed in all targeted fetuses with ultrasound examination. Dissection of fetuses demonstrated a necrotic intrathoracic lesion similar in size to the HIFU focus (approximately 1 x 9 mm). None of the surrounding fetuses was found to have bradycardia during the procedure or a macroscopic lesion on dissection. CONCLUSION: In this pilot study HIFU seems promising to ablate even highly vascularized tissue in the fetus.     

Changes in umbilical artery,middle cerebral artery,and aorta blood flow Doppler waveform pulsatility indices after funisocentesis

This study evaluates the effect of funisocentesis on umbilical artery, fetal cerebral artery, and aortic circulation. The pulsatility index in the umbilical artery, fetal middle cerebral artery, and descending aorta was measured by pulsed Doppler ultrasonography before and after 41 diagnostic funisocenteses. Percutaneous umbilical artery blood sampling was associated with a significant decrease in umbilical artery pulsatility index (mean -0.132, standard deviation 0.259, P = 0.002) and in middle cerebral artery pulsatility index (mean -0.143, standard deviation 0.260, P = 0.001). The decline in resistance to flow of the umbilical artery (r = 0.340, P = 0.029) and middle cerebral artery (r = 0.457, P = 0.002) was correlated with gestational age at sampling. These findings suggest that alterations in the waveforms from both the umbilical and the fetal cerebral circulations can be induced by fetal blood sampling.     

The impact of alpha-adrenergic stimulation on umbilical blood flow.

This study evaluated the effects of intranasal phenylephrine, an alpha-adrenergic agonist used for respiratory congestion, on uteroplacental blood flow. Twelve subjects were recruited from the Women's Clinic. Inclusion criteria were age greater than 18 years, singleton gestation, absence of medical illness and gestational age of 22-38 weeks. Phenylephrine (0.2 ml of 1% aq. solution) was applied to each nostril. Maternal blood pressure and pulse, umbilical artery velocimetry, and fetal heart rate were recorded prior to drug administration and at 5, 15, 30, 45 and 60 min after administration. There were no significant changes in maternal pulse, blood pressure or fetal heart rate. All subjects had normal baseline umbilical artery Doppler systolic/diastolic ratios. Eleven of 12 subjects demonstrated an elevation of the systolic/diastolic ratio consistent with vasoconstriction following administration. This elevation reached statistical significance at 30 min. Significant individual variation existed with regards to timing of maximal excursion of the systolic/diastolic ratio. The mean maximal change of the systolic/diastolic ratio was 1.57 +/- 1.25 (p < 0.001) ranging from -0.53 to 4.11. The use of over-the-counter alpha-adrenergic agents may result in decreased umbilical artery flow velocities. In high-risk pregnancies these medications may be contraindicated.     

Uterine and fetal cerebral Doppler predict the outcome of third-trimester small-for-gestational age fetuses with normal umbilical artery Doppler.

OBJECTIVE: To assess the value of different admission tests in predicting the outcome of small-for-gestational age (SGA) fetuses with normal Doppler waveforms in the umbilical artery. METHODS: Criteria for admission into this retrospective study included: singleton pregnancy with a birth weight < 10th centile; absence of severe maternal complications; no evidence of fetal anomalies on the sonogram; normal umbilical artery Doppler; and availability of complete follow-up. At the first antenatal sonogram classifying the fetus as SGA, Doppler analysis of the uterine and middle cerebral arteries was performed and amniotic fluid volume was assessed. Outcome variables included adverse perinatal outcome (perinatal death, severe morbidity) and emergency Cesarean section for fetal distress. RESULTS: Two hundred and thirty-one pregnancies were included in the study. The mean +/- standard deviation birth weight and gestational age at delivery were 2222 +/- 502 g and 37.3 +/- 2.9 weeks, respectively. In 37 cases (16%), an emergency Cesarean section was performed. There was one intrauterine death and three fetuses delivered by emergency Cesarean section developed severe morbidity. Logistic regression demonstrated that abnormal velocimetry of the uterine arteries and fetal middle cerebral artery were independently correlated with the occurrence of Cesarean section. CONCLUSIONS: SGA fetuses with normal umbilical artery Doppler waveforms and abnormal uterine arteries and fetal middle cerebral artery waveforms have an increased risk of developing distress and being delivered by emergency Cesarean section. Particularly when both uterine and fetal cerebral waveforms are altered at the same time, the risk is exceedingly high (86%) and delivery as soon as fetal maturity is achieved seems advisable. On the other hand, when both vessels have normal waveforms, the chances of fetal distress are small (4%) and expectant management is the most reasonable choice.