Systolic-diastolic Ratio Research Articles

Successful identification of acute renal allograft rejection with duplex ultrasonography

Duplex ultrasonography has met with variable accuracy in identifying acute renal allograft rejection. These published studies have focused on using mathematical indices. We have applied duplex ultrasonography differently by insonating the site of rejection, i.e. renal cortex, to identify by subjective analysis the changes of the velocity spectral patterns. This subjective analysis method was compared to the mathematical indices of diastolic/systolic ratio and pulsatility index in 126 episodes of clinical acute renal allograft rejection which all had biopsy correlation. This present study represents the largest published experience with duplex ultrasonography and renal transplant rejection. Subjective analysis of velocity spectral patterns (SUBJ) resulted in sensitivity of 87%, specificity of 94% and overall accuracy of 88%. This technique was statistically better than the diastolic/systolic ratio (DSR) sensitivity of 40%, specificity of 72% and overall accuracy of 49%, or the pulsatility index (PI) sensitivity of 47%, specificity of 75% and overall accuracy of 55%. The superior results of the subjective analysis technique of duplex ultrasonography to identify acute renal allograft rejection suggests that this diagnostic approach has sufficient accuracy to avoid invasive allograft biopsies.

Reference values for Doppler velocimetric indices from the fetal and placental ends of the umbilical artery during normal pregnancy.

A range-gated Doppler ultrasound system combined with a real-time imaging system was used to determine arterial blood velocity values from the fetal and placental ends of the umbilical cord in 269 normal pregnancies between 17 and 40 weeks, menstrual age. The systolic-diastolic ratio (S/D), pulsatility index (PI), and resistance index (RI) were higher at the fetal end compared to the placental end of the cord. The individual differences in these Doppler indices, obtained between the fetal and placental recording sites, were inversely related to menstrual age: S/D: r = -0.38, p < 0.001; PI: r = -0.25, p < 0.001; and RI: r = -0.15, p < 0.01. After normalization for the angle of insonation, the peak systolic velocity was higher and the end-diastolic velocity was lower at the fetal than at the placental end of the cord. It is concluded that routine recordings for Doppler velocimetric indices should take into account the recording site on the umbilical cord in order to reduce methodological sources of variance, especially during midgestation. Furthermore, the data presented here in the form of the median and percentile values are proposed as normal reference values to facilitate this procedure.

Doppler ultrasonography of the umbilical cord in complicated pregnancies.

Ninety-two gravid women had Doppler insonation of the umbilical cord after diagnosis of various pregnancy complications. Calculations of the systolic-diastolic (S/D) ratio were plotted against a nomogram of values developed at the Hospital of the University of Pennsylvania. An S/D ratio greater than the 95th percentile for gestational age correctly predicted 58% of women who became preeclamptic and 61% of infants who were small for gestational age (SGA). Of those fetuses with an elevated S/D ratio, 42% suffered fetal distress as defined by an abnormal fetal heart rate tracing, a 1- or 5-minute Apgar score less than 5 or 7, respectively, or a cord blood pH determination less than 7.20; 60% required operative delivery; and 49% stayed in the hospital longer than 5 days or were admitted to the Neonatal Intensive Care Unit (NICU). All these values are significantly greater than those obtained in a control group of uncomplicated pregnancies or a group of women with similar pregnancies, but with normal measurements of the umbilical artery S/D ratio. Moreover, 69% of abnormally elevated umbilical artery S/D ratios were detected at or before 30 weeks' gestation. Calculation of an S/D ratio of the umbilical cord greater than the 95th percentile for gestational age is an early and sensitive predictor of poor perinatal outcome.

Clinical chorioamnionitis is not predicted by umbilical artery Doppler velocimetry in patients with premature rupture of membranes

Chorioamnionitis substantially increases fetal and neonatal morbidity. Infants born to women with chorioamnionitis have a fourfold increase in neonatal morbidity. If this condition could be predicted before the clinical manifestation and thereby treated earlier, an improved perinatal outcome might reasonably be expected. Based on the in vitro model of bacteria-induced vasoconstriction and pulmonary hypertension noted in sheep and lambs after exposure to the spent medium of a bacterial culture, we theorized that infected amniotic fluid may produce vasospasm of umbilical and placental vessels, reduce fetal perfusion, and increase perinatal asphyxia, morbidity, and mortality. Umbilical vessel vasospasm may be detected by measuring the systolic-diastolic ratio (S/D) of the umbilical artery. Continuous Doppler flow studies of the umbilical artery S/D were performed prospectively on 51 patients with premature rupture of membranes who were not in labor. The most recent test, done within 1 day of delivery, was compared with pregnancy outcome. Ten subjects developed clinical chorioamnionitis, of whom none had an abnormal S/D. Six of 41 women without clinical chorioamnionitis had abnormal S/Ds. These data do not support the use of Doppler measurement of the S/D as a predictor of clinical chorioamnionitis.

Doppler Velocimetry in Concordant and Discordant Twin Gestations

Doppler blood flow studies in 63 pairs of concordant and 17 pairs of discordant twins were compared with those of 277 appropriate for gestational age singleton fetuses. Discordancy was defined as a more than 20% intra-pair actual birth weight difference. The data were divided into five groups: singletons and large and small concordant and discordant twins. Statistical comparisons of the regression lines for the large concordant and discordant twins and the singletons showed no significant differences among the three lines, either in slopes (P = .1) or intercepts (P = .08). Comparisons of the regression lines for small concordant and discordant twins and the singletons indicated a significant interaction among the three lines (P = .01). Additional analysis leads us to conclude that the systolic-diastolic ratio (S/D) decreases with advancing gestational age for all groups except small discordant twins. The S/D of small discordant twins differed significantly from that of singletons and tended to differ from that of small concordant twins.

Doppler Ultrasonography of the Umbilical Cord in Normal Pregnancy

Using continuous wave Doppler ultrasonography to measure umbilical artery flow velocity waveforms (FVWs) is a safe, noninvasive means of quantifying placental resistance to blood flow. Detection of abnormally elevated resistance to umbilical perfusion may identify pregnancies complicated by uteroplacental insufficiency. Use of this technique to identify high-risk pregnancies requires ready access to standard tables of normal FVW values obtained from well-defined populations under usual clinical conditions. We report measurements of the systolic-diastolic (S-D) ratio of the umbilical artery obtained between 16 and 43 weeks in 122 normal pregnancies. A gestational-age-adjusted table of normal values is presented.

Doppler systolic-diastolic ratios in pregnancies complicated by syphilis

Maternal infection with syphilis can result in focal areas of vasculitis and, similarly, placental villitis and obliterative arteritis. We hypothesized that Doppler systolic-diastolic ratios (S/Ds) in pregnancies complicated by maternal syphilis infection might reflect an increased resistance to placental perfusion. Doppler velocity waveform analysis was used to study the uterine and umbilical arteries in third-trimester pregnancies complicated by maternal syphilis infection. A control group of similarly studied normal pregnancies was used for comparison. Statistically significant increases were found in the mean S/Ds of both the uterine and umbilical arteries in the syphilis group compared with the normal group, indicating an increased resistance to perfusion of the placenta in pregnancies complicated by syphilis. This difference was even greater in association with the identification of spirochetes in the amniotic fluid by dark-field microscopy, indicating that the S/D results are related to the presence of intrauterine infection. Serial S/Ds in a small subgroup of patients correlated with the clinical courses, including an apparent acute vascular-resistance change associated with treatment, probably due to the Jarisch-Herxheimer reaction. Because of these post-treatment vascular events, the pre-treatment S/D alone may have a limited clinical predictive value for treatment efficacy in congenital syphilis.

Maternal, uteroplacental, and fetoplacental hemodynamic and Doppler velocimetric changes during epidural anesthesia in normal labor

Pulsed Doppler and M-mode maternal echocardiography were combined with uterine and umbilical artery Doppler velocimetry to characterize the hemodynamic changes associated with fluid preload and epidural anesthesia in 12 normal laboring gravidas at term. Fluid preload alone was associated with significant (P less than .05) increases in heart rate (11%), stroke volume (10%), and cardiac output (20%), and a decrease in systemic vascular resistance (19%). There were no changes in mean arterial pressure (MAP) or ejection fraction during any stage of the study. Following placement of the epidural block, stroke volume and cardiac output returned to values not significantly different from baseline, whereas heart rate remained elevated and systemic vascular resistance remained decreased. There were no changes in uterine or umbilical artery systolic-diastolic (S-D) ratios during any stage of the study. We conclude that fluid preload and epidural anesthesia cause significant changes in maternal cardiac output, heart rate, stroke volume, and systemic vascular resistance without affecting MAP. These maternal changes do not correlate with any changes in uterine or umbilical artery S-D ratios following epidural anesthesia in the normal laboring gravida.

The effects of epidural anesthesia on the Doppler velocimetry of umbilical and uterine arteries in normal and hypertensive patients during active term labor

To study the effects of epidural anesthesia on uterine and umbilical artery blood flow in preeclampsia, we observed 25 patients in active labor at 36 or more weeks' gestation. Seven had preeclampsia, eight had chronic hypertension, and ten had no complications. Doppler velocimetry of the uterine and umbilical arteries was performed before and after intravenous fluid loading and at 30 and 60 minutes after epidural blockade. Maternal vital signs and fetal heart rate were monitored continuously. After epidural block, mean maternal blood pressure fell significantly in all groups, but no maternal hypotension was observed. Mean maternal and fetal heart rates were unchanged. After epidural block, mean uterine artery systolic-diastolic (S-D) ratios did not change in the chronic-hypertension and normal groups, but fell significantly in the preeclamptic group to values similar to those of the normal group. Umbilical artery S-D ratios did not change in any group. In preeclamptic pregnancy, epidural anesthesia may help to reduce uterine artery vasospasm and may benefit intrapartum fetal well-being.

The Effects of Epidural Anesthesia on the Doppler Velocimetry of Umbilical and Uterine Arteries in Normal and Hypertensive Patients During Active Term Labor

To study the effects of epidural anesthesia on uterine and umbilical artery blood flow in preeclampsia, we observed 25 patients in active labor at 36 or more weeks' gestation. Seven had preeclampsia, eight had chronic hypertension, and ten had no complications. Doppler velocimetry of the uterine and umbilical arteries was performed before and after intravenous fluid loading and at 30 and 60 minutes after epidural blockade. Maternal vital signs and fetal heart rate were monitored continuously. After epidural block, mean maternal blood pressure fell significantly in all groups, but no maternal hypotension was observed. Mean maternal and fetal heart rates were unchanged. After epidural block, mean uterine artery systolic-diastolic (S-D) ratios did not change in the chronic-hypertension and normal groups, but fell significantly in the preeclamptic group to values similar to those of the normal group. Umbilical artery S-D ratios did not change in any group. In preeclamptic pregnancy, epidural anesthesia may help to reduce uterine artery vasospasm and may benefit intrapartum fetal well-being.

Effect of Premature Ventricular Contractions on Middle Cerebral Artery Blood Flow Velocity.

The effect of premature ventricular contractions on blood flow velocity in the middle cerebral artery was studied by transcranial Doppler ultrasonography in 1 0 patients. Velocity during three ectopic beats for each patient was lower than that during the preceding and the following beat in every recording. The decrease in peak velocity was 30.7 ± 12.4% and 37.1 ± 13.3% (mean ± standard deviation) compared to the preceding and following beat, respectively. This variation was significantly larger (p < 0.0001) than the spontaneous change observed during sinus rhythm, 2. 7 ± 2.2% in patients with premature ventricular contractions and 3.5 ± 3.2% in control subjects. Similar results were obtained for both mean and diastolic blood flow velocities. Systolic-diastolic ratios were similar for premature ventricular contractions, beats preceding or following premature ventricular contractions, and sinus rhythm beats. Transcranial Doppler ultrasound appears to be an excellent technique for analyzing the effects of cardiac arrhythmias on the cerebral circulation.

Relationship Between Second Trimester Maternal Serum Alpha-Fetoprotein and Umbilical Artery Doppler Velocimetry and Their Association with Preterm Delivery

One explanation for an abnormal maternal serum alpha-fetoprotein (MSAFP) may be an abnormal placenta. A specimen for MSAFP and a series of umbilical artery waveforms were obtained prior to amniocentesis from 144 consecutive women referred for either maternal age (n = 85), a persistently elevated MSAFP unassociated with a structural abnormality (n = 42), or a low MSAFP (n = 17). Almost 50% of deliveries before 37 weeks and 60% of neonatal birthweights below the tenth percentile occurred in the high MSAFP group. We observed that the systolic-diastolic ratio (S/D), pulsatility index, and resistance index tended to be higher in women referred for an elevated MSAFP. Confining analyses to the elevated MSAFP group, the MSAFP in multiples of the median correlated with birthweight independent of the gestational age at delivery (p less than 0.001). In addition, the S/D related directly to MSAFP (p less than 0.03) and indirectly to the gestational age at delivery (p less than 0.04). None of these relationships was observed in the groups of women referred for either maternal age (who had a normal MSAFP) or a low MSAFP. Employing a stepwise multiple linear regression, we found that the gestational age at delivery could be predicted during the midsecond trimester using a combination of the umbilical artery S/D and MSAFP. When the analyses and predictions were limited to subjects whose MSAFP still exceeded 2 multiples of the median at the time of amniocentesis, the positive predictive value for preterm delivery was 100% and the negative predictive value was 93%.(ABSTRACT TRUNCATED AT 250 WORDS)

Maternal angiotensin sensitivity and fetal Doppler umbilical artery flow waveforms

The angiotensin pressor response was investigated in normotensive pregnancies which had umbilical Doppler flow velocity waveforms suggestive of placental vascular disease. Of the 36 pregnancies studied at between 24 and 38 weeks gestation, 18 had a positive response to the angiotensin pressor test, these women were delivered earlier (35.3 vs 38.5 weeks, P = 0.015), had a lower mean birthweight centile (14 vs 36, P less than 0.001) and higher frequency of fetal distress in labour (40% vs 7%, P = 0.06) when compared with the 18 women who had a negative response. The Doppler umbilical systolic-diastolic (S-D) ratio decreased with gestation in the negative group, suggesting continuing placental growth and vascular expansion, whereas the S-D ratio increased in the positive group (P less than 0.001), indicative of vascular obliteration. We suggest that the positive angiotensin pressor response is primarily associated with the placental vascular pathology. Angiotensin infusion had no acute effect on maternal uteroplacental or fetal umbilical artery flow velocity waveforms.

Measurement of Systolic-Diastolic Ratio in the Umbilical Artery by Continuous-Wave and Pulsed-Wave Doppler Ultrasound: Comparison at Different Sites

Measurement of Systolic-Diastolic Ratio in the Umbilical Artery by Continuous-Wave and Pulsed-Wave Doppler Ultrasound: Comparison at Different Sites

Measurement of Systolic-Diastolic Ratio in the Umbilical Artery by Continuous-Wave and Pulsed-Wave Doppler Ultrasound: Comparison at Different Sites

Analysis of umbilical artery flow velocity waveforms, especially systolic-diastolic (S-D) ratio, can predict some pregnancy abnormalities. Most of the earlier studies did not specify the exact segment of umbilical artery sampled. We studied 53 normal singleton pregnancies between 18-41 weeks' gestation to compare S-D ratio measurements of the umbilical artery at different sites: 1) abdominal insertion site, 2) placental insertion site, 3) mid-cord, and 4) an undetermined site. The mean S-D ratio was significantly different (P less than .01) at various segments of the umbilical artery--higher near the abdominal insertion site when compared with the mid-cord, near-placental, and undetermined sites. The S-D ratio at mid-cord was higher than at the undetermined site and the placental insertion site. The near-placental-site S-D ratio was not different from the undetermined site. A lower S-D ratio at the undetermined site may not adequately reflect the true physiologic status of the fetus. Specifying the site of measurement should be an integral part of any report, in order to describe accurately the pathophysiology of fetoplacental circulatory diseases.

Doppler Systolic-Diastolic Ratios in Pregnancies Complicated by Syphilis

Maternal infection with syphilis can result in focal areas of vasculitis and, similarly, placental villitis and obliterative arteritis. We hypothesized that Doppler systolic-diastolic ratios (S/Ds) in pregnancies complicated by maternal syphilis infection might reflect an increased resistance to placental perfusion. Doppler velocity waveform analysis was used to study the uterine and umbilical arteries in third-trimester pregnancies complicated by maternal syphilis infection. A control group of similarly studied normal pregnancies was used for comparison. Statistically significant increases were found in the mean S/Ds of both the uterine and umbilical arteries in the syphilis group compared with the normal group, indicating an increased resistance to perfusion of the placenta in pregnancies complicated by syphilis. This difference was even greater in association with the identification of spirochetes in the amniotic fluid by dark-field microscopy, indicating that the S/D results are related to the presence of intrauterine infection. Serial S/Ds in a small subgroup of patients correlated with the clinical courses, including an apparent acute vascular-resistance change associated with treatment, probably due to the Jarisch-Herxheimer reaction. Because of these post-treatment vascular events, the pre-treatment S/D alone may have a limited clinical predictive value for treatment efficacy in congenital syphilis.

Effects of acute hypoxemia on umbilical arterial Doppler indices in a fetal ovine model

Changes in umbilical arterial Doppler waveform in response to acute maternal hypoxemia were assessed in a chronic ovine model. Maternal heart rate, blood gases, fetal heart rate and umbilical arterial Doppler indices measured at baseline conditions and during periods of maternal hypoxemia were compared. The indices measured were systolic-diastolic ratio (S/D), pulsatility index (PI) and resistance index (RI). Fetal heart rate decreased (< 80 beats/min) and umbilical arterial Doppler indices increased ( P < 0.001) during the periods of hypoxemia. Furthermore, the Doppler indices were highly but negatively correlated with alterations in the fetal heart rate (FHR) ( P < 0.001). Analysis of the Doppler waveform phase intervals revealed nearly constant systolic intervals while diastolic intervals varied inversely with the heart rate alterations. Moreover, the umbilical arterial Doppler indices, when corrected for FHR changes, were relatively unchanged from baseline measurements. This study indicates that maternal hypoxemia induced changes in the umbilical arterial Doppler indices may be primarily attributable to the changes in FHR.

Single Dose of Nifedipine in Normotensive Pregnancy

The short-term effect of 20 mg of oral nifedipine on maternal and fetal hemodynamics was investigated in ten healthy, normotensive women at 38 weeks' gestation admitted to the hospital for elective cesarean delivery. Within 1 hour after nifedipine administration, mean arterial pressure had decreased by 10% and a slight increase was observed in maternal heart rate. A statistically significant (P less than .01) decrease in the systolic-diastolic ratio was found in the flow velocity waveform from the uterine artery, but no change was seen in that from the arcuate artery. No changes were observed in the fetal heart rate pattern or in umbilical or thoracic aortic flow velocity waveforms. Nifedipine concentrations in the mother had no correlation with maternal or fetal hemodynamic responses. At delivery 2.5 hours after nifedipine ingestion, the umbilical venous-maternal ratio of nifedipine concentrations was 0.76.

Uterine and Umbilical Artery Flow Velocity Waveform Analysis in Pregnancies Complicated by Chronic Hypertension or Preeclampsia

Using continuous wave Doppler ultrasound, we studied the umbilical and uterine flow velocity waveforms in 68 pregnant women who had chronic hypertension and/or preeclampsia. The systolic-diastolic (S/D) ratio was considered an expression of vascular resistance peripheral to the point of insonation. Abnormal umbilical artery S/D ratio (greater than 95th percentile) alone or with abnormal uterine artery S/D ratio was associated with poor pregnancy outcome as judged by incidence of intrauterine growth retardation (IUGR), cesarean section rate, birth weight, perinatal morbidity and mortality, and prematurity. In patients with preeclampsia and abnormal Doppler values, pregnancy outcome was poor, whereas in those with normal Doppler values, pregnancy outcome approached normal. The same relationship was also found in patients with chronic hypertension. The sensitivity and specificity for the prediction of IUGR by the umbilical artery S/D ratio alone was 71% and 93%, respectively. The uterine artery S/D ratio alone yielded a 66% sensitivity and 64% specificity, and when both tests were taken into account, the sensitivity increased to 75% and the specificity to 100%. Abnormal umbilical and uterine artery S/D ratios were associated with 100% IUGR and 25% perinatal mortality. We conclude that in pregnant women with hypertensive disorders there is a significant difference in pregnancy outcome between those with normal and those with abnormal Doppler values. Umbilical artery S/D ratio alone is a better predictor of IUGR and poor pregnancy outcome than the uterine artery S/D ratio.

The effect of heart rate on Doppler flow velocity systolic-diastolic ratios in umbilical and uteroplacental arterial waveforms

In an analysis of the influence of heart rate on Doppler flow velocity waveformsystolic/diastolic ratios from 1555 umbilical artery waveform studies and from 1497 uteroplacental waveform studies, a negative correlation was observed between the ratio and the corresponding heart rate. This relationship was not influenced by gestational age and was similar in pregnancies with normal outcomes when compared with all pregnancies. The magnitude of this inverse relationship is such that the effect of heart rate on systolic/diastolic ratios must be considered when Doppler flow velocity waveform analyses are used as experimental tools to assess placental vascular resistance but it does not appear to be an important factor in general clinical practice when measurements are made during fetal inactivity and when heart rates are within normal ranges.