Heartrate variation of umbilical artery Doppler waveforms

Umbilical artery Doppler waveforms from 20 patients were used to investigate the dependence of resistance index and pulsatility index on beat to beat pulse length over short time periods for individual patients, and on the usefulness of a common normalisation formula. For individual patients the resistance index and pulsatility index were only partially correlated with pulse length. Changes in both indices occurred independently of pulse length. Use of a common normalisation formula resulted in no significant reduction of the coefficient of variation of the resistance index (p greater than 0.1), and a reduction in the coefficient of variation of the pulsatility index of 10% (p greater than 0.001). It is concluded that short term changes in resistance index and pulsatility index cannot be corrected by a common normalisation formula.     

Determination of the presence of fetal apnoea using umbilical artery and umbilical vein Doppler waveforms

Fetal breathing movements were observed using real-time ultrasound imaging. Simultaneous Doppler recordings of the flow velocity waveform from the umbilical artery and umbilical vein were obtained. Twenty patients were studied. The Doppler traces obtained during fetal apnoea and fetal breathing for each patient were analysed using a BBC microcomputer. A combination of venous variation index (VVI) and the coefficient of variation of arterial pulsatility index (CVPI) gave complete separation between breathing and apnoeic groups (lower values of VVI and CVPI being associated with the apnoeic group). Hence, when stand alone continuous wave Doppler units are used to acquire umbilical artery Doppler waveforms during fetal apnoea, the presence of apnoea can be determined using the variability of the arterial and venous trace without the need for visualisation of the fetus using imaging equipment.     

Doppler ultrasound waveforms in the fetal umbilical artery: quantitative analysis technique

Doppler ultrasound waveforms from the fetal umbilical artery were analyzed by a new quantitative technique. Normal pregnancy and cases of fetal growth failure were considered. Data from the spectrum analyzer were dumped to a microcomputer, the velocity waveforms calculated and a representative waveform obtained by ensemble averaging. This curve was then fitted by a 4-parameter analytic function. We introduce R, the relative flow rate index, which measures the ratio of the average flow rate before the systolic peak to the average rate during the remainder of the cardiac cycle. In cases of fetal growth failure this ratio was significantly greater than in normal pregnancy. Other new quantities defined are the normalized systolic decay time index and the constant flow ratio. The AB ratio was also calculated. Fetal growth failure has been associated with raised placental resistance. We suggest that the fetus can initially compensate for this by increasing cardiac contractility. This can be seen by interpreting the R and AB values together. Our analysis technique enables the waveform to be efficiently described, and provides useful diagnostic information about placental function and fetal wellbeing.     

Doppler blood velocity waveforms in the umbilical artery as an indicator of fetal well-being

Doppler blood velocity waveforms were analyzed from the umbilical artery as an indication of fetal well-being. Since the ratio of systolic to diastolic peak flows (A/B) reflects placental vascular resistance, an abnormality of this value may accurately predict compromised fetuses. Twenty-one studies were performed on 13 patients, using a new duplex system for real-time imaging and range-gated pulsed Doppler analysis, and compared to normal standards. Thirteen studies done in nine uneventful pregnancies were consistently normal. However, abnormal studies were found in the four patients reported as case histories, including women with sickle cell anemia, systemic lupus, diabetes, and growth retardation. The A/B ratio was felt to have predicted potential fetal compromise, including the two fetal deaths. Therefore, with certain cautions, we feel that this rapid, non-invasive technique is useful as a serially applicable reflector of the status of fetoplacental circulation.     

Significance of an absent or reversed end diastolic flow in Doppler umbilical artery waveforms

The outcome of nine fetuses in whom Doppler umbilical arterial velocity-time waveforms showed absence or reversal of flow in end diastole was presented. Eight of the nine resulted in either intrauterine or neonatal death. Progressive deleterious changes in the waveforms were evident in three fetuses who had serial evaluation. The remaining infant survived when delivery was expected 2 days later. Our data have indicated that the demonstration of an absent or reversed flow in end diastole in the umbilical arteries carries with it a very specific indication of serious fetal compromise and the need for immediate delivery, although the prognosis of a normal neonatal survival remains guarded.     

An investigation of simulated umbilical artery Doppler waveforms. II. A comparison of three Doppler waveform quality indices

Three Doppler waveform quality indices based upon assessment of the noise of the maximum frequency envelope of simulated umbilical artery waveforms were investigated. These indices were: an estimate of the correlation between successive waveforms (QI1), a local linearity measure (QI2) and a ratio of two regions of the Fourier transform amplitude spectrum of the maximum frequency envelope (QI3). Simulated umbilical artery waveforms were acquired from a physiological flow phantom. A test population was used consisting of a large number of waveforms where one of three physical variables had been adjusted to produce waveforms of varying quality. These three physical variables were: beam-vessel angle, beam-vessel axial misalignment and attenuator thickness. For this group of waveforms the accuracy of estimation of the maximum frequency envelope and pulsatility index (PI) were known. All three quality indices gave good separation of high- and low-quality waveforms based upon threshold values of the accuracy of PI and maximum frequency envelope. The dependence of each quality index on fetal breathing, waveform length and waveform pulsatility was investigated. QI2, the local linearity measure, showed most promise in its independence from these variables.     

Diabetes mellitus in pregnancy and the assessment of umbilical artery waveforms using pulsed Doppler ultrasonography.

The utility of Doppler ultrasonography as a means of assessing potential alterations of vascular resistance prior to fetal or maternal compromise is very attractive. We investigated this relationship by prospectively performing Doppler studies of the fetal umbilical artery in 56 diabetic patients, 14 of whom had varying degrees of vascular complications. When regression curves were established for the S/D ratio, the Pourcelot index, and the resistance index of the fetal umbilical artery, the mean Doppler values were higher in diabetic patients with vasculopathy than in nondiabetic control patients or in diabetic patients without vasculopathy. The third trimester S/D ratio was greater than 3.0 in almost 50% of patients with vasculopathy. A tendency toward adverse outcomes was observed at S/D ratios approaching 4.0. Statistically significant correlations were found between elevated Doppler indices and maternal vasculopathy associated with hypertension and worsening renal insufficiency. Intrauterine growth retardation and neonatal metabolic complications were also significantly correlated with elevated Doppler indices. There was, however, no correlation between Doppler indices and glucose values, although most were within a euglycemic range. The aforementioned data indicate an increased resistance circuit among diabetics with vasculopathy, which may reflect a relative reduction in basal uteroplacental blood flow and the need for cautious interpretation of Doppler indices in these patients.     

An investigation of simulated umbilical artery Doppler waveforms. I. The effect of three physical parameters on the maximum frequency envelope and on pulsatility index

The effect of three physical parameters on the accuracy of estimation of the maximum frequency envelope and pulsatility index (PI) of simulated umbilical artery Doppler waveforms was investigated. The physical parameters were beam-vessel angle, the offset between the beam axis and vessel axis, and the thickness of overlying attenuating material. Waveforms were acquired using a physiological flow phantom. The maximum frequency envelope was calculated using a threshold maximum frequency follower which was adaptive to the level of background noise. A gold standard maximum frequency envelope was obtained from the ensemble averaged waveform when there was alignment of beam and vessel axis, a 50 degrees beam-vessel angle and 2 cm of attenuating material. Indices of bias, variability and accuracy of estimation of the maximum frequency envelope and PI were calculated by comparing subsequent maximum frequency envelopes with the gold standard maximum frequency envelope. Both the maximum frequency envelope and PI were estimated to a similar degree of accuracy over a wide range of physical conditions. In this study, the error in PI was less than 0.15 for beam-vessel angles less than 80 degrees, for beam-vessel axis offset distances less than 7.5 mm, at a transducer-vessel distance of 5 cm, and for attenuator thicknesses less than 4.5 cm. The percentage root-mean square error for estimation of the maximum frequency envelope was approximately 10% or less for beam-vessel angles less than 75 degrees, for beam-vessel axis offset distances less than 7.5 mm, and for attenuator thicknesses less than 4 cm.     

彩色多普勒超声监测生长迟缓胎儿脐动脉血液循环的变化

目的 应用彩色多普勒超声监测生长迟缓（IUGR）胎儿的脐动脉血液循环。方法 测定130例妊娠20－42周妇女（其中正常49例,IUGR81例）脐动脉时间平均血流速度（TAMX）,收缩期最大血流速度与舒张末期血流速度的比值（S／D）,搏动指数（PI）,阻力指数（RI）,收缩期最大血流速度（Vmax)与舒张末期血流速度（Vmin)。结果 正常孕妇随孕龄增长,胎盘功能增强,胎儿血液循环日渐丰富,IUGR者则明显障碍,在20周时脐动脉TAMX显著下降,在30周后S／D,PI及RI显著升高,Vmin显著下降,在35周时Vmax显著下降,出现舒张期血流停止或倒流。结论 彩色多普勒超声可直接测定脐动脉血流循环,能在早期诊断UGR,判断病情及估计预后。     

An investigation of simulated umbilical artery Doppler waveforms. III. The effect of noise reduction algorithms on the maximum frequency envelope and on the pulsatility index.

The effect of two noise reduction algorithms on the accuracy of estimation of the maximum frequency envelope and pulsatility index (PI) of simulated umbilical artery Doppler waveforms was investigated. The algorithms were: first, smoothing of the envelope from unfiltered Doppler spectra using a double window modified trimmed mean (DWMTM) filter and second, speckle and noise reduction of the Doppler spectrum using an image processing method. The test population consisted of waveforms were the degree of beam-vessel misalignment had been varied. The accuracy of estimation of the maximum frequency envelope and the PI was calculated by comparing each set of waveforms with the gold-standard maximum frequency envelope from the ensemble averaged waveform obtained with no misalignment. Speckle reduction gave rise to PI values that were low by approximately 0.1 (3%-4%). When there was no background noise present the improvements in envelope estimation were factors of 1.27 and 1.24, respectively, for the DWMTM method and the spectral filter, whereas the factors were 1.56 and 2.07 when background noise was present. For estimation of PI the DWMTM filter was superior. For no background noise the DWMTM filter gave a factor of 3.36 improvement whereas there was no improvement with the spectral filter. When background noise was present the factors for improvement in PI estimation were 2.39 and 4.16.     

Pulsatility index of superior mesenteric artery blood velocity waveforms

A transcutaneous Doppler ultrasound technique was used to investigate superior mesenteric artery blood velocity waveforms in normal subjects. The shape of the waveforms was quantified by means of the pulsatility index (PI). The mean value +/- standard error of the mean of the PI measured in 82 normal subjects in the resting and fasting state was 3.57 +/- 0.11. There was no difference in the PI between sexes nor correlation between the PI and age. Following the ingestion of a meal in a group of 15 subjects the PI decreased by 46% (p less than 0.001). A significant fall persisted over the next two hours.     

The effect of altitude on the umbilical artery Doppler resistance.

This study examined whether there were differences between the umbilical artery systolic-diastolic (S/D) ratio and resistance index (RI) in patients with normal fetuses living at sea level (group I) and those living between 4,200 and 4,500 feet above sea level (group II). Linear regression demonstrated a significant association (P less than 0.001) between gestational age and the S/D ratio and RI for groups I (n = 100) and II (n = 128). Least-squares regression analysis demonstrated no significant differences in slopes or intercepts between groups I and II. The results would suggest that altitude, up to 4,500 feet above sea level, does not affect umbilical artery Doppler resistance in normal fetuses.     

彩色多普勒对脐绕颈胎儿脐动脉及大脑中动脉血流检测分析

目的　分析脐绕颈胎儿脐动脉 (UA)及大脑中动脉 (MCA)的血流参数 ,为临床判断胎儿脑供血情况提供客观依据。方法　比较 44例脐绕颈剖腹产胎儿与 61例脐绕颈自然分娩胎儿的脐动脉及大脑中动脉血流多普勒参数 ,以RI及VP为分析指标。结果　该两组脐绕颈胎儿UA的RI及VP有显著性差异 ,MCA的RI有显著性差异 ,剖腹产胎儿MCA的血流特点为阻力增高 (RI 0 67± 0 0 2 )。结论　脐绕颈胎儿MCA的血流阻力增高 (RI >0 65 )应作为剖腹产术的临床参考指标     

多种方法联合评价脐动脉多普勒信号的临床应用

目的：探讨多种方法联合评价胎儿脐动脉多普勒信号的临床价值。方法：将71例妊娠20－41周的妇女分为正常组（56例）和病理妊娠组（15例）。用彩色多普勒超声测得胎儿脐动脉多普勒信号，将此信号以音频形式输入计算机，分别以零极点模型、Teagar能量法和分形方法进行信号分析，同时常规计算脐动脉收缩期最大血流速度（S）与舒张期末血流速度（D）的比值（S／D）。以多元决策法综合上述4种方法的特征参数评价脐动脉多普勒信号。结果：对病理妊娠组，利用常规S／D法、零极点模型法、Teagar能量法、分形法的异常率分别为26．67％、66．67％、53．33％和46．67％。利用多元决策法，病理妊娠组异常率为80．00％，与前4种方法相比差异有显著性意义（P＜0．05）。结论：利用多元决策法分析脐动脉血流信号能敏感、客观、准确地反映病理状态下的脐血流改变。     

Carotid and vertebral artery Doppler ultrasound waveforms: a pictorial review

Carotid and vertebral artery spectral Doppler ultrasound waveforms can be affected by many types of local lesions, proximal cardiovascular disease, and devices, as well as distal cerebrovascular disease. Recognizing abnormal spectral Doppler ultrasound waveforms and their significance is important for proper management. Examples of normal and abnormal carotid and vertebral artery spectral Doppler ultrasound waveforms are reviewed and illustrated in this pictorial review.     

Umbilical artery Doppler blood velocity waveforms in normal and abnormal gestations

Blood velocity patterns in peripheral arteries reflect hemodynamic characteristics, particularly systemic vascular resistance. Doppler blood velocity waveforms in umbilical arteries (UA) indirectly assess placental vascular resistance (P1VR) and therefore an abnormal waveform value may serve as an index of placental insufficiency associated with elevated P1VR. We prospectively studied the ratio of peak-systolic to end-diastolic velocities (A/B ratio) in the UA of 113 normal fetuses on 121 occasions over a period of 4 years. A range-gated, pulsed Doppler, duplex, two-dimensional, real-time echocardiogram (ECHO) allowed placement of the sample volume in the UA by direct vision; hard copy of the tracing was later analyzed. Hand calipers allowed measurement of the fetal cardiac cycle length (RR) and A/B ratio, which were compared with gestational age (EGA), echo-derived total cardiac dimension (TCD), and aortic root size (AO). Normative data were analyzed by least squares linear regression and compared to data in several high-risk groups. In the normal fetus, there was an orderly pattern with advancing gestational age of linearly decreasing A/B ratio and increasing TCD, AO, and RR. The A/B ratio varied inversely with TCD and AO, but was independent of RR. In a group of 20 hypertensive patients, 6 had elevated A/B ratios; of 18 diabetic pregnancies, 4 had elevated A/B ratios. In other high-risk groups, 4 of 21 patients were abnormal: sickle-cell disease (1 case), systemic lupus erythematosus (1 case), and intrauterine growth retardation (2 cases). In conclusion, Doppler A/B ratios in the UA of normal patients, like cardiac size, show an orderly pattern of change with EGA independent of RR.(ABSTRACT TRUNCATED AT 250 WORDS)     

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.     

Umbilical artery Doppler flow-velocity waveforms and fetal acid-base balance in Rhesus-isoimmunized pregnancies

Pulsed Doppler blood-flow velocity waveforms in the umbilical arteries, as well as blood gases, hematocrit, and lactate concentration in umbilical venous blood, were examined in 21 patients undergoing 49 cordocentesis, 34 of which were followed by fetal blood transfusion into the umbilical vein. The aim of the study was to evaluate the correlations, if any, between the Doppler indices from the umbilical artery (pulsatility index, resistance index, systolic/diastolic ratio) and the blood gas values (pO₂, pCO₂, O₂ content, pH) and lactate content in the umbilical vein. The only correlation confirmed in this study was in the subgroup of anemic fetuses undergoing fetal blood transfusion, where correlation existed between A/B and the initial O₂ content (r = ?0.41, p < 0.02). We conclude that, in Rhesus-isoimmunized pregnancies, in contrast to other pregnancies, a close correlation does not exist between the Doppler indices in the umbilical artery and the fetal blood gas values. © 1994 John Wiley & Sons, Inc.