Intertwin discordance in umbilical venous volume flow: a reflection of blood volume imbalance in twin-to-twin transfusion syndrome.

OBJECTIVES: To compare umbilical venous volume flow (UVVF) between donor and recipient twins in twin-to-twin transfusion syndrome (TTTS) using an index that is independent of gestational age and to correlate changes in this index with outcome following endoscopic laser surgery. METHODS: UVVF was calculated in 84 cases of TTTS by multiplying the umbilical vein cross-sectional area at its entry into the fetal abdomen by time averaged blood velocity. All cases were classified according to the Quintero staging system. The ratio between UVVF in recipients and donors (R/D-UVVF) in each pair of twins was calculated before and 48 h after laser treatment, and changes in R/D-UVVF were correlated with pregnancy outcome. Intraobserver and interobserver UVVF measurement reliability was assessed in 19 singletons, and 13 donor and recipient twins before laser treatment using the intraclass correlation coefficient (ICC). RESULTS: Twenty-five, 32, 21 and six cases presented as Quintero Stages 1, 2, 3 and 4, respectively, at a median gestational age of 20 (range, 15-26) weeks. Intraobserver and interobserver ICC for UVVF measurement in twins were 0.97 and 0.67, respectively. UVVF was a median of 2.13-fold (range, 0.3-19-fold) higher in recipients than in donors (137 mL/min vs. 64 mL/min, P < 0.001) and increased with gestational age (r = 0.58, P < 0.001 for recipients, r = 0.62, P < 0.001 for donors). From 68 cases in which R/D-UVVF could be measured 48 h following laser surgery, cases with a favorable outcome showed a significant decrease in R/D-UVVF from a median of 1.97 to 1.27 (P < 0.01) and cases with recurrent TTTS (n = 6) did not (decrease in R/D-UVVF from a median of 2.32 to 2.19, P = 0.17). Using a cut-off of < 30% reduction of R/D-UVVF, 66% of the cases with recurrence could be predicted, and the odds ratio for recurrence was 3.13 (95% CI, 0.52-18.29). A significant UVVF imbalance between recipient and donor twins was found in cases with Quintero Stages 1-3 but not in those with Stage 4. CONCLUSIONS: In TTTS, UVVF is significantly higher in recipients than in their donor cotwins and the R/D-UVVF seems adequately to indicate the flow imbalance between twins, regardless of gestational age. A decrease in R/D-UVVF could be predictive of a favorable evolution following laser treatment.     

The effect of fetoscopic laser therapy on fetal cardiac size in twin-twin transfusion syndrome.

OBJECTIVES: To evaluate the influence of fetoscopic laser therapy on fetal cardiac size in monochorionic twins complicated by twin-twin transfusion syndrome (TTTS). METHODS: In a longitudinal, prospective study, we assessed fetal cardiac size sonographically in monochorionic diamniotic twins with TTTS treated by laser therapy and in monochorionic twins without TTTS. The fetal cardiothoracic ratio (cardiac circumference divided by thoracic circumference) of TTTS twins was determined within 24 h before, 12-24 h after and 1 week after laser treatment, and from then on every 2-4 weeks until birth. TTTS twins were classified into Quintero Stages 1-2 (n = 18) and Stages 3-4 (n = 16), and measurements were compared with biweekly measurements of non-TTTS monochorionic twins matched for gestational age (n = 38). Cardiomegaly was defined as a cardiothoracic ratio above the 97.5th percentile. RESULTS: Before laser treatment, cardiomegaly was observed in 44% (8/18) and 50% (8/16) of recipients in Quintero Stages 1-2 and Stages 3-4, respectively. Cardiomegaly occurred in none of the donors before treatment. After laser treatment, cardiomegaly was observed in 76% (13/17) and 50% (7/14) of recipients in Stages 1-2 and Stages 3-4, respectively, and in 17% (3/18) and 13% (2/15) of donors in Stages 1-2 and Stages 3-4, respectively. Cardiomegaly was present in 18% (7/38) and 8% (2/25) of non-TTTS monochorionic twins and singletons. After laser therapy, the cardiothoracic ratio of recipients in Stages 1-2 and Stages 3-4 was not significantly changed (P = 0.34 and P = 0.67, respectively). The cardiothoracic ratio of donors in Stages 1-2 and Stages 3-4 was increased compared with that before laser therapy (P = 0.0002 and P = 0.005, respectively). Cardiothoracic ratios of non-TTTS monochorionic twins were not significantly different from our reference range in singletons throughout gestation, and were smaller than those in both recipients and donors after laser therapy. CONCLUSIONS: TTTS recipients show cardiomegaly before as well as after fetoscopic laser therapy for TTTS. Donors develop cardiomegaly only after laser treatment. Our findings emphasize the significant effect of TTTS and fetoscopic laser therapy on the fetal heart of both recipient and donor twins.     

Ultrasound assessment of venous blood flow before and after laser therapy: approach to understanding the pathophysiology of twin-twin transfusion syndrome.

OBJECTIVE: To estimate direction and volume of blood exchange between the donor twin and recipient twin by ultrasound assessment of blood flow in the umbilical vein before and after selective laser photocoagulation of communicating vessels (SLPCV) for twin-twin transfusion syndrome (TTTS). METHODS: Forty-one TTTS patients underwent Doppler examination of the umbilical vein before and 24 h after SLPCV. The diameter and mean time-averaged velocity of the umbilical vein were estimated. Total umbilical venous flow (TUVF) was calculated as follows: TUVF (mL/min) = mean time-averaged velocity (cm/s) x mean cross-sectional area (cm2) x 60 (s). RESULTS: TUVF was significantly higher in the recipient (111.2 mL/min) than in the donor twin (44.8 mL/min) before SLPCV (P < 0.0001). However, TUVF was no different between the recipient and the donor twin after SLPCV (93.1 vs. 70.7 mL/min, recipient and donor twin, respectively, P = 0.11). The donor twin's TUVF increased after surgery (P < 0.0001), while the recipient twin's TUVF decreased (P = 0.041). The median postoperative increase in the donor twin's TUVF of 25.9 mL/min had a corresponding decrease of TUVF in the recipient twin of 18.1 mL/min (P = 0.27). CONCLUSIONS: Our data suggest that untreated TTTS is characterized by excessive umbilical venous blood flow in the recipient twin relative to the donor twin. Laser surgery results in concordant changes in umbilical venous flow in opposite directions between the donor and recipient twins, eliminating the initial imbalance. Our results lend support to the fundamental hypothesis of unbalanced blood flow exchange (net flow from donor to recipient) between monochorionic twins as the cause for TTTS and that laser surgery eliminates the pathophysiological cause.     

Impact of laser coagulation in severe twin-twin transfusion syndrome on fetal Doppler indices and venous blood flow volume.

OBJECTIVE: To evaluate the impact of fetoscopic laser coagulation of placental anastomoses in severe twin-twin transfusion syndrome on fetal Doppler indices and umbilical vein blood flow volume as calculated with Doppler and two-dimensional ultrasound. METHODS: Thirty-two cases of second-trimester severe twin-twin transfusion undergoing laser therapy were examined with serial ultrasound before and 1, 3 and 5 days after therapy. Pulsatility indices in the umbilical artery and ductus venosus were measured. Blood volume flow at the level of the intra-abdominal umbilical vein was calculated by means of Doppler and two-dimensional ultrasound. The development of hydropic signs in donors was recorded. Perinatal outcome in terms of neonatal survival was recorded for all cases. RESULTS: In recipients, ductus venosus pulsatility index decreased progressively after therapy and, by day 5, median pulsatility index was significantly lower than that before therapy (0.97 vs. 0.82, P < 0.0001). Umbilical vein blood flow volume in recipient twins showed no significant variations before and after laser. In donors, umbilical artery pulsatility index decreased significantly by the first day following therapy (2.1 vs. 1.6, P < 0.0001). Previously absent or reverse umbilical end-diastolic flow reappeared after therapy in 46% (7/15) of donors. Ductus venosus pulsatility index in donors increased significantly by day 1 after therapy (0.99 vs. 1.35, P < 0.0001) but, over days 3 and 5, it returned towards preoperative values. Umbilical vein flow volume measurements (mL/min/kg) in the donor increased by approximately 50% the day after treatment (151 vs. 232, P < 0.0001) and remained elevated. Umbilical vein flow volume before laser therapy was significantly lower in donors compared to recipients (151 vs. 260, P < 0.0001), but the difference was non-significant after treatment (240 vs. 267). One or more hydropic signs developed in eight (25%) donors during the 5 days' observation after therapy. CONCLUSIONS: Laser therapy induced important changes in fetal hemodynamic parameters, resulting in a reversion of the disturbances associated with severe twin-twin transfusion syndrome. The recipient twin showed a progressive improvement of previous signs of right cardiac overload. The donor experienced a substantial increase in umbilical vein blood volume flow accompanied by a transitory state of relative right overload, which may explain the development of transient hydropic signs in a proportion of donors.     

Analysis of fetal growth after laser therapy in twin-to-twin transfusion syndrome.

OBJECTIVE: The purpose of this study was to evaluate fetal growth patterns after laser therapy in twin-to-twin transfusion syndrome (TTTS). METHODS: All cases with delivery after 24 weeks from pregnancies complicated by TTTS treated by laser therapy between January 1999 and September 2004 were included. Fetal biometric parameters and estimated fetal weight were measured by sonography at least twice before laser therapy and twice after laser therapy. The interval between sonographic measurements was at least 2 weeks. The study population was divided into group I, which consisted of pregnancies with 2 liveborn neonates, and group II, which consisted of pregnancies resulting in only 1 liveborn neonate. The z scores for biometric measurements were calculated in all cases accordingly and compared for each twin across gestational age by analysis of variance and between groups by a t test. In group I, the intertwin discordance was also assessed, and analysis of variance was used to compare mean values across gestational age. RESULTS: Ninety-eight cases with 51 single and 47 double liveborn neonates were included. Across time, z scores of the recipients significantly decreased, whereas there was no change in z scores of the donors. The z scores were not statistically different between groups. There was a significant decrease in fetal discordance after laser therapy in group I. CONCLUSIONS: The fetal growth pattern in TTTS can change after laser treatment. There is a slowdown in the recipient growth and maintained growth in the donor twin. Both mechanisms lead to a decrease in intertwin discordance.     

The role of Doppler studies in predicting individual intrauterine fetal demise after laser therapy for twin-twin transfusion syndrome.

OBJECTIVE: To investigate the role of Doppler studies in predicting individual fetal demise in patients scheduled for selective laser photocoagulation of communicating vessels (SLPCV) for twin-twin transfusion syndrome (TTTS). METHODS: Doppler studies of the umbilical artery, umbilical vein, ductus venosus, tricuspid valve regurgitation and middle cerebral artery were performed in the donor and recipient twins before and 24 hours after SLPCV. Results were analyzed cross-sectionally and longitudinally. As multiple comparisons were made, an a priori alpha rejection was set at P < 0.001. RESULTS: One hundred and ten consecutive patients were available for analysis. Overall fetal survival was 68.6% (151/220) with at least one survivor in 88.2% (97/110) of cases. Absent or reversed end-diastolic velocity in the umbilical artery of the donor twin was the only preoperative Doppler result predictive of intrauterine fetal demise (IUFD) (10/15, 66.7%, P < 0.001). Postoperatively, reversed flow during atrial contraction in the ductus venosus of the donor twin showed a trend towards prediction of IUFD of this fetus (4/5, 80%, P = 0.007). No other Doppler studies, including the longitudinal analyses, were predictive of IUFD. CONCLUSIONS: Our data suggest that preoperative absent or reversed end-diastolic velocity in the umbilical artery may be useful in predicting individual fetal demise of the donor twin in TTTS patients scheduled for SLPCV. This may reflect the role of decreased individual placental mass that may be associated with some donor twins. The inability of other Doppler studies to predict individual IUFD may be explained preoperatively by the effect of the interfetal vascular connections on the individual Doppler signals and postoperatively by the effect of surgery or the timing of the assessment. Our findings may be important in patient counseling, in furthering understanding of the disease, and perhaps in improving surgical technique.     

Early manifestations and spectrum of recipient twin cardiomyopathy in twin-twin transfusion syndrome: relation to Quintero stage.

OBJECTIVES: To examine cardiac structural and functional changes in twin-twin transfusion syndrome (TTTS), relative to Quintero stage, as a means of evaluating the spectrum of cardiomyopathy in TTTS. METHODS: This was a cross-sectional, retrospective study of 42 consecutive cases of TTTS referred to a single fetal therapy center. Quintero stages were assigned by standard criteria. Presence of ventricular hypertrophy, cardiomegaly, atrioventricular valve regurgitation (AVVR), ventricular systolic dysfunction and right ventricular outflow tract obstruction on fetal echocardiography were noted. The Doppler myocardial performance index (MPI), an index of global ventricular function, was calculated for both ventricles in subjects with adequate Doppler data. We compared cardiac changes across Quintero stages. RESULTS: There was no cardiomyopathy observed in donor twins. The majority of subjects presented at Quintero Stage I (n = 14), II (n = 14) or III (n = 11), with fewer at Stages IV (n = 2) or V (n = 1). As early as Quintero Stages I and II, a significant proportion of recipient twins had ventricular hypertrophy (17/28, 61%), AVVR (6/28, 21%) or quantitative abnormalities in either right (12/24, 50%) or left (14/24, 58%) ventricular function. Increasing prevalence of biventricular systolic dysfunction and cardiomegaly accompanied advancing Quintero stage. CONCLUSIONS: Changes in cardiac structure and function not reflected in Quintero staging occur in recipient twins early in the evolution of TTTS. Incorporation of cardiac findings into assessment of TTTS severity may prove useful in stratification of risk and treatment selection.     

Prognostic factors in severe twin-twin transfusion syndrome treated by endoscopic laser surgery.

OBJECTIVE: The aim of this study was to investigate clinical and sonographic parameters, in particular Doppler blood flow measurements, in severe second-trimester twin-twin transfusion syndrome before and after endoscopic laser coagulation of the placental vascular anastomoses, to correlate these data with fetal outcome and to determine whether fetal blood flow measurements could help to estimate the probability of fetal survival. METHODS: In 121 cases of severe twin-twin transfusion syndrome examined between 17 and 26 weeks of gestation, the following investigations were performed: fetal biometry, placental location, deepest pool of amniotic fluid, echocardiography and Doppler sonography of the umbilical arteries and the ductus venosus of both twins before and after fetoscopic laser ablation of the placental anastomoses. RESULTS: The overall survival rate was 64% (156/242). Both fetuses survived in 48% (58/121) and one fetus survived in 33% (40/121), resulting in 81% (98/121) of pregnancies with at least one survivor. Gestational age at the time of the procedure and placental location had no significant influence on fetal survival. The amniotic fluid volume drained after laser coagulation correlated significantly (p = 0.038) with the risk of miscarriage or extremely premature delivery within 4 weeks of the procedure. Intertwin discrepancy in abdominal circumference showed a significant negative correlation (p = 0.004) with the probability for survival of donor fetuses. Before the procedure, 19% (23/121) of donor twins and 5% (6/121) of recipient twins showed absent or reversed end-diastolic flow in the umbilical artery (p = 0.001). This finding had no significant influence on the survival rate of donors. An increase of waveform indices in the umbilical artery 1 day after the procedure compared to immediately after the procedure correlated significantly with a lower probability for survival of donors (p = 0.042) and recipients (p = 0.018). Before the procedure, 37% (45/121) of recipient twins and 9% (10/113) of donor twins showed absent or reversed flow during atrial contraction in the ductus venosus (p < 0.0001). This finding had a significant negative influence on the survival rate of recipient fetuses (p = 0.02). Furthermore, an increase of waveform indices in the ductus venosus 1 day after the procedure compared to immediately after the procedure correlated significantly with a lower probability of survival in recipients (p = 0.005). CONCLUSIONS: Fetoscopic laser coagulation of the placental vascular anastomoses in severe mid-trimester twin-twin transfusion is a potentially corrective and effective, minimally invasive procedure. Doppler investigation of the umbilical and fetal circulations provides important information on the fetal condition, prognosis and therapeutic effects of the intervention. Signs of congestive heart failure in the recipient may reduce the probability of survival, whereas increased placental resistance in the donor before the procedure is not necessarily associated with a reduction in the probability of survival after laser coagulation.     

Selective versus non-selective laser photocoagulation of placental vessels in twin-to-twin transfusion syndrome.

OBJECTIVE: We have recently described a surgical technique for the treatment of twin-to-twin transfusion syndrome (TTTS) that allows precise identification of vascular anastomoses (selective laser photocoagulation of communicating vessels, or S-LPCV). The purpose of this study was to compare S-LPCV with the previous non-selective technique (NS-LPCV) that targeted all vessels crossing the dividing membrane. MATERIALS AND METHODS: Patients with TTTS were treated with NS-LPCV from May 1994 to June 1997 and with S-LPCV from July 1997 to December 1999. TTTS was defined as polyhydramnios of > or = 8 cm maximum vertical pocket (MVP) in the recipient twin and oligohydramnios of < or = 2 cm MVP in the donor twin. Outcome was measured as survival per number of pregnancies and per number of fetuses together with limited morbidity data. RESULTS: NS-LPCV was used in 18 patients and 74 were treated with S-LPCV. Three patients interrupted their pregnancies electively after surgery (S-LPCV) and were removed from further analysis. Survival of at least one fetus was higher in S-LPCV (83.1%) than in NS-LPCV (61.1%) (P = 0.04), mostly due to a lower rate of dual intra-uterine fetal demise in S-LPCV (5.6%) than in NS-LPCV (22%) (P = 0.05). There were more hydropic fetuses in the NS-LPCV group (27%) than in the S-LPCV group (5.4%), but this difference did not account for the results. There was no difference in the survival per number of fetuses between the two groups. CONCLUSIONS: S-LPCV represents an important evolution in the surgical treatment of TTTS. The use of this technique by all centers should allow better comparison of fetal survival and morbidity rates. S-LPCV should be the standard technique in trials comparing amniocentesis versus laser for the treatment of severe TTTS.     

Umbilical cord occlusion of the donor versus recipient fetus in twin-twin transfusion syndrome.

OBJECTIVES: To compare the technical characteristics and perinatal outcomes of selected twin-twin transfusion syndrome (TTTS) cases treated with primary umbilical cord occlusion (UCO) of the donor vs. recipient twin. METHODS: TTTS patients who underwent primary UCO via ultrasound endoscopic-guided umbilical cord ligation (UCL) or endoscopic umbilical cord photocoagulation (UCP) were eligible for the study. Primary UCO was offered only if a discordant lethal anomaly was present or by patient choice in TTTS Stages III/IV on the cord of the fetus with abnormal Doppler studies or hydrops. RESULTS: Primary UCO was performed in 25 TTTS cases between July 1997 and June 2002. UCO was performed in six (24%) donor twins and 19 (76%) recipient twins. UCL was performed in 23 cases and UCP in two cases. Overall, 22 (88%) patients had liveborn infants. There were no differences in cotwin survival (100% vs. 84.2%), median gestational age at delivery (34.8 vs. 33.8 weeks) and preterm premature rupture of membranes rate (16.6% vs. 15.7%) whether the donor or recipient twin, respectively, was the subject of UCO. However, two-trocar access (50% vs. 5.3%; P = 0.03) and amnioinfusion (83.3% vs. 0%; P < 0.001) were required more often in the UCO of the donor than of the recipient twin, respectively. Operating time (75 vs. 40 min) was significantly longer in UCO of the donor twin (P = 0.04). UCP was more likely to be used in occlusion of the donor's cord (33%) than of the recipient's cord (0%; P = 0.05). CONCLUSION: Primary UCO of the donor twin is technically more demanding than that of the recipient twin, but perinatal outcomes of the cotwins are comparable.     

双胎输血综合征激光治疗前后脐动脉血流指数的超声研究

目的 探讨双胎输血综合征胎盘血管吻合支激光阻断前后胎儿脐动脉血流指数的改变.方法 对9例超声诊断双胎输血综合征孕妇行超声引导下胎盘血管交通支激光阻断术,观察手术前后胎儿脐动脉血流指数的改变.结果 手术前后供血胎儿脐动脉搏动指数、收缩期峰值血流速度与舒张末期血流速度比值有明显改变,差异有统计学意义(均P<0.01),而受血胎儿手术前后脐动脉阻力指数差异有统计学意义(P<0.01).结论 超声观察胎盘血管吻合支激光阻断术前后脐动脉血流指数改变有助于临床判断手术疗效与预后.     

Normalization of Amniotic Fluid Levels After Fetoscopic Laser Surgery for Twin‐Twin Transfusion Syndrome

Objective. The purpose of this study was to describe amniotic fluid (AF) normalization after laser surgery for twin‐twin transfusion syndrome (TTTS). Methods. Patients with TTTS (n = 174) who had laser surgery from 2006 through 2009 underwent serial measurements of the AF maximum vertical pockets (MVPs) during postoperative weeks 1 through 10. A normal MVP was defined as greater than 2 cm and less than 8 cm. Postoperative TTTS criteria required an MVP of 2 cm or less in one sac and 8 cm or greater in the other sac. Patients with septostomy, immediate fetal death, or missing MVP values were excluded. Results. Inclusion criteria were met by 115 patients. Normalization of the MVP occurred by week 5 in donors and week 8 in recipients in approximately 95% of the cases. Recipient fetuses with Quintero stage 3 or 4 TTTS (J Perinatol 1999; 19:550–555) were more likely to have an abnormal MVP than those with stage 1 or 2 TTTS during weeks 3 and 4 (P = .0049) and 5 and 6 (P = .0239). The criteria for TTTS were met in 6 cases (6.9%) in week 1: 5 resolved spontaneously, and 1 (1.2%) had persistent TTTS and required a second laser surgery. After week 1, 6 additional patients had abnormal MVP values for both fetuses simultaneously: 1 met TTTS criteria in week 3; 2 had oligohydramnios in week 2; and 3 had polyhydramnios in weeks 2, 4, and 7; none of these patients required further interventions. Conclusions. Although the AF of individual donor and recipient fetuses may take several weeks to normalize after laser surgery for TTTS, it is rare for both fetuses to meet TTTS criteria beyond the first postoperative week.     

Relevance of measuring diastolic time intervals in the ductus venosus during the early stages of twin-twin transfusion syndrome.

OBJECTIVE: To determine if the discrete myocardial diastolic dysfunction documented previously in the recipient twin during the early stages of twin-twin transfusion syndrome (TTTS) has any repercussion on flow velocities through the ductus venosus (DV) and to investigate if this could allow early differentiation between TTTS and selective intrauterine growth restriction (IUGR). METHODS: Two groups of monochorionic twin pregnancies with growth discordance between twins were reviewed retrospectively. Group I was composed of fetuses in Stages I and II of TTTS; laser or amnioreduction was not performed in any instance. Group II twin pairs each included one fetus with IUGR due to placental circulatory insufficiency. Intertwin differences (smaller minus larger fetus) were analyzed for myocardial performance index of the right ventricle (MPI-RV) and for time variables in the DV. RESULTS: There were 38 pairs of monochorionic twins (24 TTTS and 14 IUGR) in this study. In the TTTS group, the donors had a significantly lower MPI-RV (0.419 +/- 0.18 vs. 0.596 +/- 0.17, F(1,19df) = 24.017, P < 0.001), a significantly longer total ventricular filling time (150.9 +/- 25.6 ms vs. 124.0 +/- 22.6 ms; F(1,21df) = 19.631, P < 0.001) and a significantly longer early filling time (118.9 +/- 22.9 ms vs. 92.6 +/- 18.9 ms, F(1,21df) = 28.419, P < 0.001) than had the recipient. None of these three differences was present in the IUGR group. Probability studies revealed that cut-off values of 12.75 for intertwin differences in total filling time and 8.5 for intertwin differences in early filling time had sensitivities of 71% and 92%, respectively. The false-positive rates were 23% and 15%, respectively, for the early diagnosis of TTTS. CONCLUSION: In monochorionic twin pregnancies, shortening of the ventricular filling time in the recipient twin indicates diastolic myocardial dysfunction occurring early in the pathophysiology of TTTS. This early interwin difference in myocardial function is not found in pregnancies with IUGR in one twin due to placental circulatory insufficiency, allowing early differentiation between TTTS and selective IUGR.     

Impact of altered loading conditions on ventricular performance in fetuses with congenital cystic adenomatoid malformation and twin-twin transfusion syndrome.

OBJECTIVES: In the fetus with a structurally normal heart, two conditions--giant chest mass, such as congenital cystic adenomatoid malformation (CCAM), and twin-twin transfusion syndrome (TTTS)--alter ventricular loading conditions and may result in cardiovascular compromise. The aim of this study was to elucidate the mechanism of cardiovascular dysfunction by comparing geometry-independent, Doppler flow-derived measures of ventricular performance in fetuses with altered loading conditions vs. those in normal fetuses. METHODS: Doppler flow-derived measures of myocardial performance index (MPI) as described by Tei, ventricular ejection force as described by Isaaz, and combined cardiac output (CCO) were obtained by echocardiography in fetuses with a normal cardiovascular system (n = 76) or CCAM (n = 36) and fetal partners with TTTS (n = 22). RESULTS: In the CCAM group, systolic performance as evidenced by the ejection forces was preserved, right ventricular (RV) MPI was increased and CCO diminished, suggesting diastolic dysfunction and poor filling secondary to cardiac compression and a tamponade effect. In TTTS, recipient twins exhibited greater left ventricular (LV) ejection forces and higher CCO than donor twins, and had abnormal RV and LV MPI, reflecting increased preload, preserved left systolic performance, but diastolic dysfunction. Donor twins had diminished ejection forces and CCO in comparison with normal controls and recipient partners, reflecting hypovolemia. CONCLUSIONS: In both CCAM and recipient twins of the TTTS, diastolic dysfunction plays a significant role in the pathophysiology of each disorder and precedes changes in systolic performance. Measures of ventricular performance can help elucidate poorly understood mechanisms of cardiovascular compromise in the developing fetus.     

Classification of discordant fetal growth may contribute to risk stratification in monochorionic twin pregnancies.

OBJECTIVES: To determine whether classification of discordant growth between fetal twins allows risk stratification in monochorionic twin pregnancies. METHODS: In 12 twin-to-twin transfusion syndrome (TTTS) pregnancies and 12 cases that were suspected of developing the syndrome, fetal growth was determined by serial standard sonography. Fetal growth was expressed as the difference-average-ratio (DAR), defined as the difference in estimated fetal weight between both twins divided by their average weight. In each case, we determined the maximum value of DAR and the rate of change of DAR using a least squares linear fit of the estimated fetal weights. RESULTS: For the TTTS cases the maximum value of DAR was 0.44 +/- 0.21 versus 0.52 +/- 0.13 for the suspected TTTS cases (P = 0.25). The rate of change of DAR was 0.052 +/- 0.034 per week for the TTTS versus 0.0055 +/- 0.0092 for the suspected TTTS cases (P = 0.0004). After laser therapy, DAR decreased in four successful cases, with a rate of change of -0.0146 +/- 0.0093 per week, but increased further in one unsuccessful case, due to patent anastomoses. In the seven TTTS cases treated with amnioreduction, DAR did not decrease; in one of two suspected TTTS cases the DAR decreased slightly. In the nine amnioreduction cases, the average rate of change of DAR was 0.067 +/- 0.083 per week. This was significantly different from the four successful laser cases (P = 0.01). CONCLUSIONS: The rate of change of DAR, but not DAR itself, has prognostic value for the development of suspected TTTS pregnancies, for the onset and severity of TTTS and for the efficacy of therapy. This parameter is derived from routine sonography examination and may contribute to risk stratification in monochorionic twin pregnancies.     

Percent absent end-diastolic velocity in the umbilical artery waveform as a predictor of intrauterine fetal demise of the donor twin after selective laser photocoagulation of communicating vessels in twin-twin transfusion syndrome.

OBJECTIVE: Absent end-diastolic velocity (AEDV) in the umbilical artery of the donor twin is a known risk factor for intrauterine fetal demise (IUFD) of this fetus after selective laser photocoagulation of communicating vessels (SLPCV) for twin-twin transfusion syndrome (TTTS). The aim of this study was to assess the proportion of time, expressed as a percentage, of the cardiac cycle spent in AEDV (%AEDV) as a predictor of IUFD of the donor. METHODS: All patients referred for possible SLPCV underwent complete preoperative staging evaluation including Doppler assessment of the umbilical artery. %AEDV was calculated retrospectively as 100 x (time of the cycle spent in AEDV divided by duration of total cardiac cycle). Patients without AEDV were considered to have a %AEDV of 0. Follow-up Doppler studies were performed 16-24 h after SLPCV. IUFD of the donor was recorded if the donor twin died any time prior to delivery. RESULTS: Of 401 patients undergoing SLPCV, 127 had AEDV. Preoperative AEDV of the donor twin was associated with an increased risk of IUFD of the donor (40.9% vs. 14.2%, P < 0.0001). %AEDV was measured in 72/127 (56.7%) donors with AEDV for whom digital images were available. Within these 72 patients, the mean %AEDV was significantly higher in patients with IUFD of the donor (36.5% vs. 29.6%, P = 0.01). IUFD of the donor was similar in patients with AEDV, regardless of whether %AEDV was measured (36% vs. 47%, P = 0.2). A %AEDV > 30 was associated with a 4.3-fold increase in the risk of IUFD of the donor (95% CI, 1.4-12.7), a sensitivity of 77% and a negative predictive value of 81.3%. Logistic regression showed that %AEDV, but not number of anastomoses, placental location, presence of artery-to-artery anastomoses or the presence or absence of EDV was associated significantly with IUFD of the donor. CONCLUSION: %AEDV is a novel Doppler parameter in the assessment of patients with TTTS. %AEDV, rather than AEDV alone, is a significant risk factor for IUFD of the donor twin and %AEDV > 30 is associated with an increased risk of IUFD of the donor in TTTS patients treated with SLPCV. Assessment of %AEDV should be considered part of the preoperative evaluation of TTTS patients.     

Stage I twin-twin transfusion syndrome: rates of progression and regression in relation to outcome.

OBJECTIVES: Twin-twin transfusion syndrome (TTTS) results in high rates of perinatal mortality and neurological morbidity. Fetoscopic laser ablation of placental anastomoses is now established as the treatment of choice for advanced disease. However, there remains controversy about its use in early-stage TTTS, in which laser-related fetal losses need to be balanced against relatively favorable outcomes with more conservative approaches. We investigated rates of progression and regression in Stage I TTTS and determined factors influencing the course of the disease. METHODS: We undertook a retrospective observational study of all TTTS cases referred to our tertiary referral fetal medicine service from 2000 to 2006. In patients presenting with Stage I TTTS, the following variables were evaluated for their ability to predict the course and progression of the disease: gestational age (GA) at presentation, amniotic fluid index, recipient and donor deepest vertical pool, presence of artery-artery anastomoses, small-sized bladder compared to normal donor bladder and fetal size discordance. Study end-points were disease regression or progression, and neonatal survival at 28 days. RESULTS: Among 132 consecutive cases of TTTS, 46 women presented with Stage I disease. In the majority (69.6%), disease remained stable (28.3%) or regressed (41.3%). Of cases that progressed, 79% did so within 2 weeks and 93% progressed to at least Stage III. No factor was significantly linked with progression or regression, although there was a trend towards the absence of an artery-artery anastomosis (P = 0.10) and the presence of a small rather than normal donor bladder (P = 0.10) influencing progression, and later GA at presentation (P = 0.07) influencing regression. At least one infant survived in 83% of cases and there was double survival in 59%. Perinatal outcome was significantly better in cases that regressed (the rates of at least one survivor and double survival being 89% and 89%, respectively) or remained Stage I (77% and 61%, respectively), compared with those cases that progressed (79% and 14%, respectively). Treatment with amnioreduction at first presentation did not influence progression or regression. CONCLUSIONS: This study demonstrates that a high percentage of Stage I TTTS cases regress or remain early stage. Identification of factors predicting progression would facilitate the selection of patients for definitive therapy, while avoiding treatment-related morbidities in mild or transient disease.     

Maternal hemodynamic changes following treatment by laser coagulation of placental vascular anastomoses and amnioreduction in twin-to-twin transfusion syndrome.

OBJECTIVES: To investigate maternal hemodynamic changes following laser therapy and amnioreduction in twin-to-twin transfusion syndrome (TTTS). METHODS: Thirty-nine cases with severe TTTS were treated at 16-26 weeks of gestation. Maternal hemodynamic evaluation was performed, including heart rate (HR), arterial pressure and echocardiography with calculation of shortening fraction (SF), left atrial dimensions, stroke volume (SV), cardiac output (CO) and total vascular resistance (TVR), before and 6 h and 24 h after placental surgery. Hemoglobin (Hb), hematocrit (Ht) and protein levels were also measured. Cases were retrospectively divided into groups according to treatment: Group A had laser therapy followed by amnioreduction >1000 mL (n = 25); Group B had laser therapy followed by amnioreduction <1000 mL (n = 14). RESULTS: The mean gestational age at inclusion was 21 (range, 16-26) weeks. The mean amniotic fluid withdrawal was 1700 (range, 1000-3000) and 300 (range, 150-800) mL in Groups A and B, respectively. Cases in Group A showed a decrease in mean arterial blood pressure (P = 0.011) and in TVR (P < 0.0001) and an increase in CO (P = 0.008) and SV (P = 0.022). There was no difference in HR. Significant hemodilution developed as early as 6 h after the procedure, with a reduction in Ht (P < 0.0001), plasma protein (P < 0.0001) and Hb levels of 1.2 g/dL on average (P < 0.0001). There were no changes in any parameters in Group B. CONCLUSIONS: Amnioreduction of severe polyhydramnios in TTTS induces maternal hemodynamic changes within the first 6 h that persist at least 24 h after treatment. These adaptative changes are compatible with hemodilution.     

速度向量成像评价双胎输血综合征胎儿心肌力学的探讨

目的 应用速度向量成像技术分析双胎输血综合征供血胎儿和受血胎儿的心功能改变,探讨两者之间的心肌力学差异.方法 动态采集30例双胎输血综合征胎儿和30例孕龄匹配的正常对照胎JL--维标准四腔心数字化图像,用心肌速度向量软件分析左室(LV)和右室(RV)长轴方向心肌应变(S)、收缩期应变率(SRs)和舒张期应变率(SRd).结果 与正常对照组相比,供血胎儿左室SRs升高,右室SRd明显减低.而受血胎儿左室和右室的S、SRs和SRd均明显减低.结论 双胎输血综合征中供血胎儿和受血胎儿的心功能均有所改变,供血胎儿左室收缩功能代偿性增强而右室舒张功能减弱,受血胎儿则表现为心肌功能广泛减退.

Abstract：

Objective To investigate the differences in myocardial deformation between donor and recipient in twin-twin transfusion syndrome(TTTS) using vector velocity imaging( VVI). Methods Digital dynamic two-dimensional four chamber views were interrogated off-line using VVI software. Global longitudinal strain(S) , systolic strain rate(SRs) and diastolic strain rate(SRd) were measured in the left ventricles(LV) and right ventricles (RV) of 30 fetal pairs with TTTS and compared to 30 gestational age-matched normal controls. Results Donor LV-SRs was higher, while donor RV-SRd was significantly lower than controls. Recipient S, SRs and SRd were significantly lower for both LV and RV in comparison to controls. Conclusions In TTTS,donor LV systolic function is hyperdynamic while the RV diastolic function is low. Recipient RV and LV are both globally depressed with systolic and diastolic dysfunction.     

Fetal echocardiographic findings are not predictive of death in twin-twin transfusion syndrome.

OBJECTIVE: The purpose of this study was to determine whether fetal echocardiographic findings are predictive of prognosis in recipient fetuses with twin-twin transfusion syndrome (TTTS). METHODS: A cohort of 30 pregnancies with TTTS between 1990 and 2001 was included. Diagnosis and staging of TTTS were made according to the Quintero system. Fetal echocardiographic findings of cardiomegaly, right ventricular hypertrophy, and tricuspid regurgitation were evaluated for relationship with fetal death. Power analysis revealed an approximately 80% power to detect a 2-fold increased risk of fetal death, with alpha = .05. Logistic regression was used to determine the relationship between echocardiographic findings and death. RESULTS: Most pregnancies were Quintero stage 1, n = 13 (43%), and ranged in severity to Quintero stage 5, n = 4 (13%). Cardiac findings in the recipient fetus that were assessed for a relationship with death included cardiomegaly at the initial appearance of TTTS or at the most severe evaluation findings, right ventricular hypertrophy at initial appearance or at the most severe evaluation findings, or tricuspid regurgitation at initial appearance or at the most severe evaluation findings. Fetal or neonatal death in the recipient twin was not related to the presence of cardiac findings (odds ratio, 0.77; 95% confidence interval, 0.16-3.74). CONCLUSIONS: Fetal echocardiographic findings, whether evaluated at initial appearance or over the course of serial evaluations, were not related to fetal or neonatal death in recipient twins with TTTS.