Characterization of a simplified ice-free cryopreservation method for heart valves.

The aim of the present study was to characterize the hemocompatibility of ice-free cryopreserved heart valves in anticipation of future human trials. Porcine pulmonary heart valves were infiltrated with either an 83 % cryoprotectant solution followed by rapid cooling and storage at --80 °C or with 10 % DMSO and control rate freezing to --80 °C and storage in vapor phase nitrogen as conventional frozen controls. Cryopreserved leaflets were compared with fresh, decellularized and glutaraldehyde-fixed control valve leaflets using a battery of coagulation protein assays after exposure to human blood. Von Willebrand Factor staining indicated that most of the endothelium was lost during valve processing prior to cryopreservation. Hemocompatibility, employing thrombin/antithrombin-III-complex, polymorphonuclear neutrophil-elastase, beta-thromboglobulin and terminal complement complex SC5b-9, was preserved compared with both fresh and frozen leaflets. Hemocompatibility differences were observed for cryopreserved leaflets versus both decellularized and glutaraldehyde fixed controls. In conclusion, the hemocompatibility results support the use of ice-free cryopreservation as a simplified preservation method because no statistically significant differences in hemocompatibility were observed between the two cryopreservation methods and fresh untreated controls.

Vascular limb occlusion in twin-twin transfusion syndrome (TTTS): case series and literature review.

OBJECTIVE: The purpose of this study was to evaluate the phenomenon of vascular ischemic limb necrosis in twin-twin transfusion syndrome (TTTS). STUDY DESIGN: This was a multicenter retrospective review of ischemic limb necrosis in patients with TTTS. RESULTS: Twenty cases of fetal ischemic limb necrosis in association with TTTS were identified from 10 fetal medicine centers. The recipient was affected in 19 cases, and the lower limb was affected in 17 cases. The extent of the damage correlated with TTTS severity. Eighty percent of limb defects (16/20) clearly were unrelated to laser treatment (3 cases untreated, 7 cases after amnioreduction, 6 cases present at time of laser). The recipient was relatively polycythemic in 5 of 7 cases in which neonatal or fetal hemoglobin/hematocrit levels were available. CONCLUSION: Ischemic limb necrosis is a rare complication of TTTS. The lesion is unrelated to therapy and may be the result of polycythemia, hypertension, and vasoconstriction.

Oligonucleotide and Parylene Surface Coating of Polystyrene and ePTFE for Improved Endothelial Cell Attachment and Hemocompatibility.

In vivo self-endothelialization by endothelial cell adhesion on cardiovascular implants is highly desirable. DNA-oligonucleotides are an intriguing coating material with nonimmunogenic characteristics and the feasibility of easy and rapid chemical fabrication. The objective of this study was the creation of cell adhesive DNA-oligonucleotide coatings on vascular implant surfaces. DNA-oligonucleotides immobilized by adsorption on parylene (poly(monoaminomethyl-para-xylene)) coated polystyrene and ePTFE were resistant to high shear stress (9.5 N/m(2)) and human blood serum for up to 96 h. Adhesion of murine endothelial progenitor cells, HUVECs and endothelial cells from human adult saphenous veins as well as viability over a period of 14 days of HUVECs on oligonucleotide coated samples under dynamic culture conditions was significantly enhanced (P < 0.05). Oligonucleotide-coated surfaces revealed low thrombogenicity and excellent hemocompatibility after incubation with human blood. These properties suggest the suitability of immobilization of DNA-oligonucleotides for biofunctionalization of blood vessel substitutes for improved in vivo endothelialization.

Preclinical evaluation of ice-free cryopreserved arteries: structural integrity and hemocompatibility.

OBJECTIVE: Arterial allografts are routinely employed for reconstruction of infected prosthetic grafts. Usually, banked cryopreserved arteries are used; however, existing conventional freezing cryopreservation techniques applied to arteries are expensive. In contrast, a new ice-free cryopreservation technique results in processing, storage and shipping methods that are technically simpler and potentially less costly. The objective of this study was to determine whether or not ice-free cryopreservation causes tissue changes that might preclude clinical use. METHODS: Conventionally frozen cryopreserved porcine arteries were compared with ice-free cryopreserved arteries and untreated fresh controls using morphological (light, scanning electron and laser scanning microscopy), viability (alamarBlue assay) and hemocompatibility methods (blood cell adhesion, thrombin/antithrombin-III-complex, polymorphonuclear neutrophil-elastase, ß-thromboglobulin and terminal complement complex SC5b-9). RESULTS: No statistically significant structural or hemocompatibility differences between ice-free cryopreserved and frozen tissues were detectable. There were no quantitative differences observed for either autofluorescence (elastin) or second harmonic generation (collagen) measured by laser scanning microscopy. Cell viability in ice-free cryopreserved arteries was significantly reduced compared to fresh and frozen tissues (p < 0.05). CONCLUSIONS: The formation of ice in aortic artery preservation did not make a difference in histology, structure or thrombogenicity, but significantly increased viability compared with a preservation method that precludes ice formation. Reduced cell viability should not reduce in vivo performance. Therefore, ice-free cryopreservation is a potentially safe and cost-effective technique for the cryopreservation of blood vessel allografts.

Development of a simplified ice-free cryopreservation method for heart valves employing VS83, an 83% cryoprotectant formulation.

We have previously demonstrated storage of ice-free cryopreserved heart valves at -80°C without the need for liquid nitrogen, with the aims of decreasing manufacturing costs and reducing employee safety hazards. The objectives of the present study were a further simplification of the ice-free cryopreservation method and characterization of tissue viability. Porcine pulmonary heart valves were permeated with an 83% cryoprotectant solution (VS83) followed by rapid cooling and storage at -80°C. The cryoprotectants were added and removed in either single or multiple steps. Fresh untreated frozen controls employing 10% dimethylsulfoxide and controlled rate freezing to -80°C, and storage in vapor phase nitrogen were also performed. After rewarming and washing, cryopreserved leaflets were compared with fresh controls using the resazurin reduction metabolism assay. Comparison of valve tissues in which the cryoprotectants were added and removed in either single or multiple steps demonstrated similar viability results for the muscle, conduit, and leaflet components. The ice-free cryopreserved conduit and leaflet components were significantly less viable than either fresh or frozen tissues. The muscle component, although less viable, was not significantly different. The changes in tissue viability were a function of cryoprotectant exposure, and resulting cytotoxicity, not temperature reduction during storage. TUNEL staining showed that ice-free cryopreservation did not induce significant amounts of apoptosis, suggesting that necrosis is the predominant cell death pathway in ice-free cryopreserved heart valves. There was very little difference in cell viability when the cryoprotectants were added and removed in a single step versus multiple steps. Ice-free cryopreserved valve tissues demonstrated very low viability compared with controls. These results support further simplification of the ice-free cryopreservation method.

Changes in umbilical venous volume flow after fetoscopic laser occlusion of placental vascular anastomoses in twin-to-twin transfusion syndrome.

OBJECTIVE: To examine effects of fetoscopic laser occlusion of placental vascular anastomoses on umbilical venous volume flow in twin-to-twin transfusion syndrome. STUDY DESIGN: Absolute umbilical venous volume flow, measured preoperatively and 48 hours after fetoscopic laser occlusion was related to Doppler studies, bladder filling in donors, and anastomoses. RESULTS: Among 45 patients, recipients had decreased ductus venosus pulsatility index (ductus venosus-pulsatility index for veins, 1.16 vs 1.01; P < .001) and unchanged umbilical venous volume flow after fetoscopic laser occlusion (74.7 vs 74.5 mL; P = .407). Donors had decreased umbilical artery pulsatility (1.34 vs 1.11; P = .008), increased ductus venous-pulsatility index for veins (0.75 vs 0.91; P < .014), and significantly increased umbilical venous volume flow per kilogram by 52.3% (136.6 vs 208.0 mL/Kg/min; P < .001). Donor bladder filling occurred at higher umbilical venous volume flow per kilogram (142.7 vs 221.4 mL/Kg/min; P < .012). Increase in umbilical venous volume flow per kilogram correlated with the net difference in arteriovenous anastomoses (Pearson r = 0.403, P = .006). CONCLUSION: Fetoscopic laser occlusion in twin-to-twin transfusion syndrome corrects intertwin differences in umbilical venous volume flow by predominant effects in the donor. Reappearance of donor bladder filling correlates with correction of volume flow.

The performance of ice-free cryopreserved heart valve allografts in an orthotopic pulmonary sheep model.

Transplantation of cryopreserved heart valves (allografts) is limited by immune responses, inflammation, subsequent structural deterioration and an expensive infrastructure. In previous studies we demonstrated that conventional frozen cryopreservation (FC) is accompanied by serious alterations of extracellular matrix (ECM) structures. As the main culprit of the observed damages ice crystal formation was identified. Objective of this study was the application principles of cryoprotection as observed in nature, occurring in animals or plants, for ice-free cryopreservation (IFC) of heart valves. Using IFC, valves were processed and stored above the glass transition temperature of the cryoprotectant formulation (-124 degrees C) at -80 degrees C to avoid any ice formation, tissue-glass cracking and preserving ECM. After implantation in the orthotopic pulmonary position in sheep, we demonstrate that IFC resulted in cell free matrices, while maintaining crucial ECM-components such as elastin and collagen, translating into superior hemodynamics. In contrast, we reveal that FC valves showed ECM damage that was not restored in vivo, and T-cell inflammation of the stroma with significant leaflet thickening. Compared to currently applied FC practice IFC also reduced infrastructural needs for preservation, storage and shipping. These results have important implications for clinical valve transplantation including the promise of better long-term function and lower costs.

Simplified pulse reactor for real-time long-term in vitro testing of biological heart valves.

Long-term function of biological heart valve prostheses (BHV) is limited by structural deterioration leading to failure with associated arterial hypertension. The objective of this work was development of an easy to handle real-time pulse reactor for evaluation of biological and tissue engineered heart valves under different pressures and long-term conditions. The pulse reactor was made of medical grade materials for placement in a 37 degrees C incubator. Heart valves were mounted in a housing disc moving horizontally in culture medium within a cylindrical culture reservoir. The microprocessor-controlled system was driven by pressure resulting in a cardiac-like cycle enabling competent opening and closing of the leaflets with adjustable pulse rates and pressures between 0.25 to 2 Hz and up to 180/80 mmHg, respectively. A custom-made imaging system with an integrated high-speed camera and image processing software allow calculation of effective orifice areas during cardiac cycle. This simple pulse reactor design allows reproducible generation of patient-like pressure conditions and data collection during long-term experiments.

The role of ultrasound examination in the first trimester and at 16 weeks' gestation to predict fetal complications in monochorionic diamniotic twin pregnancies.

OBJECTIVE: The purpose of this study was to determine the value of ultrasound examination in the first trimester and at 16 weeks to predict fetal complications in monochorionic diamniotic (MCDA) twin pregnancies, defined as the occurrence of either twin-to-twin transfusion syndrome, severe discordant growth, or intrauterine death. STUDY DESIGN: We identified risk factors to predict a complicated fetal outcome in the first trimester and at 16 weeks in a prospective cohort of 202 twin pregnancies recruited during the first trimester in 2 centers of the EuroTwin2Twin project. RESULTS: Significant predictors in the first trimester were the difference in crown-rump length (odds ratio [OR], 11) and discordant amniotic fluid (OR, 10). At 16 weeks, significant predictors were the difference in abdominal circumference (OR, 29), discordant amniotic fluid (OR, 7), and discordant cord insertions (OR, 3). Risk assessment in the first trimester and at 16 weeks detected 29% and 48% of cases with a complicated fetal outcome, respectively, with a false-positive rate of 3% and 6%, respectively. Combined first-trimester and 16 week assessment identified 58% of fetal complications, with a false-positive rate of 8%. CONCLUSION: Of the MCDA twin pregnancies classified as high risk on the combined first trimester and 16 weeks assessment (n = 41), 73% had a complicated fetal outcome with a survival rate of only 69%. In contrast, of the pregnancies classified as low risk (n = 154), 86% had an uneventful fetal outcome with a survival rate of 95%.

Clinical outcome and placental characteristics of monochorionic diamniotic twin pairs with early- and late-onset discordant growth.

OBJECTIVE: The purpose of this study was to examine the clinical and placental characteristics of monochorionic diamniotic twin pregnancies with early-onset discordant growth diagnosed at 20 weeks, late-onset discordant growth diagnosed at 26 weeks or later, and concordant growth. STUDY DESIGN: We studied a prospective cohort that underwent an ultrasound scan in the first trimester, at 16, 20, and 26 weeks. We excluded pregnancies complicated by twin-to-twin transfusion syndrome, miscarriage, fetal death less than 16 weeks, or severe congenital anomalies. Placental sharing and angioarchitecture were assessed by injection of each cord vessel with dyed barium sulphate. The 2 territories were delineated on an X-ray angiogram. The diameter of each intertwin anastomosis was measured on a digital photograph. RESULTS: We included 178 twin pairs. Early onset discordant growth, late-onset discordant growth, and concordant growth occurred in 15, 13, and 150 pregnancies, respectively. Twin pairs with early-onset discordant growth had lower survival rates and were delivered at an earlier gestational age than pairs with late-onset discordant and concordant growth. The degree of birthweight discordance was similar in early- and late-onset discordant growth. Severe intertwin hemoglobin differences at the time of birth occurred in 0%, 38%, and 3% of pairs with early-onset discordant growth, late-onset discordant growth, and concordant growth, respectively. The placentas of pairs with early-onset discordant growth were more unequally shared and had larger arterioarterial anastomoses and a larger total anastomotic diameter as compared with placentas of pairs with late onset-discordant or concordant growth. CONCLUSION: Unequal placental sharing appears to be involved in the etiology of early-onset discordant growth, whereas a late intertwin transfusion imbalance may be involved in some cases with late-onset discordant growth.

The outcome of monochorionic diamniotic twin gestations in the era of invasive fetal therapy: a prospective cohort study.

OBJECTIVE: The purpose of this study was to document pregnancy and neonatal outcome of monochorionic diamniotic twin pregnancies. STUDY DESIGN: This observational study describes a prospective series included in the first trimester in 2 centers of the Eurotwin2twin project. RESULTS: Of the 202 included twin pairs, 172 (85%) resulted in 2 survivors, 15 (7.5%) in 1 survivor, and 15 (7.5%) in no survivors. The mortality was 45 of 404 (11%), and 36 of 45 (80%) were fetal losses of 24 weeks or less, 5 of 45 (11%) between 24 weeks and birth, and 4 of 45 (9%) were neonatal deaths. Twin-to-twin transfusion syndrome (TTTS) occurred in 18 of 202 (9%). The mortality of TTTS was 20 of 36 (55%), which accounted for 20 of 45 (44%) of all losses. Severe discordant growth without TTTS occurred in 29 of 202 (14%). Its mortality was 5 of 58 (9%), which accounted for 5 of 45 (11%) of all losses. Major discordant congenital anomalies occurred in 12 of 202 (6%). Of the 178 pairs that continued after 24 weeks, 10 (6%) had severe hemoglobin differences at birth. After 32 weeks, the prospective risk of intrauterine demise was 2 in 161 pregnancies (1.2%; 95% confidence interval, 0.3-4.6). CONCLUSION: Of the monochorionic twins recruited in the first trimester, 85% resulted in the survival of both twins, and 92.5% resulted in the survival of at least 1 twin. Most losses were at 24 weeks or less, and TTTS was the most important cause of death. After 32 weeks, the risk of intrauterine demise appears to be small.

Fetal adiponectin and resistin in correlation with birth weight difference in monozygotic twins with discordant growth.

BACKGROUND: Various studies have demonstrated an increased risk for adult diseases in newborns born small-for-gestational-age (SGA). Adiponectin and resistin can be detected in cord blood and are suggested to affect insulin resistance (IR). This might represent a link between metabolic syndrome and SGA birth. STUDY DESIGN: We investigated the relationship between the adipocytokines and inter-twin birth weight (BW) difference of 31 monozygotic twins with twin-twin transfusion syndrome; in 14 twin pairs BW difference was >15% (1 SGA twin, 1 appropriate-for-gestational-age, AGA, twin). RESULTS: BW and length of all patients were positively related to adiponectin (r = 0.57; p < 0.0001; r = 0.47; p < 0.0001) and to resistin (r = 0.31; p < 0.01; r = 0.35; p < 0.01). In 71% (10/14), the SGA twins showed lower adiponectin concentrations than their AGA co-twins (only 6/14 for resistin). To correct for gestational age we calculated the relationship between the intrapair differences (Delta) of BW and Delta of the hormones. We found Delta BW positively correlated with adiponectin (r = 0.55; p < 0.001) but not with resistin (r = 0.22; p = 0.2). Delta adiponectin was positively correlated with Delta resistin (r = 0.45; p < 0.01). CONCLUSION: These data demonstrate that adiponectin and resistin levels are associated with BW with only adiponectin levels being reduced in SGA children independently of gestational age. Prenatally different metabolic status between the twins might predispose the SGA twin to develop IR later in life.

Placental sharing, birthweight discordance, and vascular anastomoses in monochorionic diamniotic twin placentas.

OBJECTIVE: The purpose of this study was to examine the relationship between placental territory and birthweight discordance and vascular anastomoses in monochorionic diamniotic twin placentas from pregnancies that were not complicated by twin-to-twin transfusion syndrome with 2 liveborn twins. STUDY DESIGN: Placentas originated from a prospective follow-up study of monochorionic diamniotic twins included in the first trimester. After injection with dyed barium sulphate, a digital x-ray angiography and high-resolution digital photograph were taken. The 2 venous territories were delineated on the angiogram. The diameter of each arterioarterial anastomosis and of each vein that participated in an arteriovenous anastomosis was measured on the digital photograph. Net transfusion over the arteriovenous anastomoses was calculated as the difference between the total venous diameters of the 2 placental parts. RESULTS: One hundred placentas were analyzed. Birthweight discordance increased with placental territory discordance (P < .0001). Arterioarterial diameter (P < .01), net arteriovenous transfusion (P < .001), and total anastomotic diameter (P < .01) increased with placental territory discordance. On the other hand, birthweight discordance for a given placental territory discordance decreased with increasing arterioarterial diameter (P < .01), net arteriovenous transfusion (P < .001), and total anastomotic diameter (P < .01). CONCLUSION: In unequally shared placentas, the 2 fetal circulations are more tightly linked than in equally shared placentas, which may reduce the birthweight discordance for a given placental territory discordance.

Immune functions after severe twin-twin transfusion syndrome.

Long-term immune functions after intrauterine laser treatment for severe twin-twin transfusion syndrome was investigated. Immunologic parameters were measured in 18 twin pairs at a median age of 3.5 years. Both donors and recipients showed no severe deficiencies in total and specific immunoglobulin concentrations.

Stage-related outcome in twin-twin transfusion syndrome treated by fetoscopic laser coagulation.

OBJECTIVE: To assess perinatal outcome in monochorionic twin pregnancies according to different stages of severe mid-trimester twin-twin transfusion syndrome managed by fetoscopic laser coagulation of the placental vascular anastomoses. METHODS: In a prospective study fetoscopic laser therapy was performed in 200 consecutive pregnancies with severe mid-trimester twin-twin transfusion syndrome at a median gestational age of 20.7 weeks (range 15.9-25.3 weeks). Outcome data were analyzed for the whole group and separately for each stage according to the Quintero staging system. RESULTS: The overall survival rate was 71.5% (286/400), with survival of both twins in 59.5% (119/200) and survival of at least one of the twins in 83.5% (167/200). The median gestational age at delivery of liveborn neonates was 34.3 weeks (range 23.1-40.4 weeks). There was a significant trend toward reduced survival rates with increasing stage (P=.038). The percentage of pregnancies with survival of both fetuses was 75.9% (22/29) for stage I, 60.5% (49/81) for stage II, 53.8% (43/80) for stage III, and 50% (5/10) for stage IV. At least one of the twins survived in 93.1% (27/29) at stage I, 82.7% (67/81) at stage II, 82.5% (66/80) at stage III, and 70% (7/10) at stage IV. The overall survival rate for donor fetuses was 70.5% (141/200) and for recipient fetuses, 72.5% (145/200). CONCLUSION: These data show that laser therapy is an effective therapeutic option for all stages of severe twin-twin transfusion syndrome and provide information to counsel patients according to the stage of the syndrome.

Cord blood leptin and IGF-I in relation to birth weight differences and head circumference in monozygotic twins.

OBJECTIVES: To investigate a potential role of leptin and insulin-like growth factor (IGF)-I on fetal growth and metabolic function we determined plasma leptin and IGF-I concentrations in twins in relation to discordant fetal growth. STUDY DESIGN: In studying monochorionic twins with inter-twin birth weight difference, we investigated the relative contribution of genetic (fetus) versus environmental (maternal/placental) factors on growth. Thirty-six sets of twins (14 with discordant growth, birth weight difference >15%) who had been treated for severe twin-to-twin transfusion syndrome (TTTS) by laser coagulation were studied. Cord blood samples were collected at birth and analyzed for IGF-I and leptin. Inter-twin differences (delta) of birth weight and head circumference were correlated to delta hormone levels. RESULTS: An inter-twin correlation for leptin (r = 0.69; p <0.0001) and delta IGF-I (r = 0.49; p <0.0001) was found. delta birth weight correlated significantly with delta IGF-I (r = 0.67; p <0.0001) but not with delta leptin (r = 0.23; p = 0.19). delta IGF-I concentrations did not correlate with delta leptin (r = 0.18). delta head circumference correlated significantly with delta leptin (r = 0.47; p <0.01) and with delta IGF-I (r = 0.46; p <0.01). Using a multiple regression model with head circumference as dependent variable, adjusted for gestational age, head circumference remained significantly associated with higher leptin concentrations in all patients (p = 0.03). CONCLUSION: IGF-I is a good indicator for fetal growth and brain development. Leptin seems to be mainly genetically determined but may play a role in fetal brain development and is not only an index for fetal fat mass.

Long-term neurodevelopmental outcome of 167 children after intrauterine laser treatment for severe twin-twin transfusion syndrome.

OBJECTIVE: This study was undertaken to investigate long-term neurodevelopmental outcome of children born after intrauterine laser coagulation for severe twin-twin transfusion syndrome. STUDY DESIGN: One hundred sixty-seven surviving infants treated between June 1997 and September 1999 were investigated at a median age of 3 years and 2 months. All children underwent a detailed standardized physical and neurologic examination and a standardized developmental test (Griffiths' Developmental Test Scales and Snijders-Oomen Non-Verbal-Intelligence Test). RESULTS: One hundred forty-five infants (86.8%) showed normal development, 12 infants (7.2%) showed minor neurologic abnormalities, and 10 infants (6.0%) major neurologic abnormalities. There was no difference in outcome for the former donors/recipients (P = .349) and between infants who were born as twins or singletons (P = .088). CONCLUSION: With a high rate (86.8%) of normal neurodevelopmental outcome and an incidence of only 6.0% of major neurologic deficiencies, intrauterine laser coagulation seems to be the best treatment option for severe twin-twin transfusion syndrome.

Fetal insulin-like growth factor (IGF)-I, IGF-II, and ghrelin in association with birth weight and postnatal growth in monozygotic twins with discordant growth.

OBJECTIVE: To investigate the relative contribution of genetic (fetal) vs. environmental (maternal/placental) factors on growth, we studied monozygotic twins with intertwin birth weight difference. PATIENTS AND METHODS: Twenty-seven twins (15 with discordant growth) who have been treated for severe twin-to-twin transfusion syndrome by laser coagulation were studied. Cord blood samples were analyzed for IGF-I, IGF-II, IGF-binding protein-2, and ghrelin. Intertwin difference (Delta) of birth weight was correlated to Delta of the parameters analyzed. The Delta weight after 1 yr was correlated with Delta birth weight and all hormones. RESULTS: The Delta birth weight was positively correlated with Delta IGF-I (r = 0.66; P < 0.0002) and negatively correlated with Delta IGF-binding protein-2 levels (r = -0.68; P < 0.001) but with neither Delta IGF-II nor Delta ghrelin. There was a strong intertwin correlation for all hormones. By comparing the growth in the first year, we found an overall reduction of the relative weight difference between the twins of 57%. ANOVA was used to calculate factors for prediction of postnatal catch-up growth. Besides the birth weight difference (R2= 0.84; P < 0.0001), only ghrelin was of prognostic value for postnatal catch-up growth (R2= 0.94; P = 0.0035). CONCLUSION: These data confirm the importance of IGF-I in contrast to IGF-II for fetal weight. Additionally, ghrelin seems to be involved in fetal and probably postnatal growth.

Amniotic fluid and maternal blood characteristics in severe mid-trimester twin-twin transfusion syndrome.

OBJECTIVE: To investigate the concentrations of metabolic variables in the amniotic fluid of the recipient twin and maternal blood and to correlate them with clinical features, which are characteristic for the course of pregnancies with twin-twin transfusion syndrome (TTS). MATERIALS AND METHODS: In 109 pregnancies with severe mid-trimester TTS, we measured the concentrations of interleukin-6 (IL-6), alpha-fetoprotein (AFP), sodium, potassium, total protein, beta2-microglobulin and osmolality in the amniotic fluid of the recipient twin prior to laser coagulation of the vascular anastomoses and compared them to a control group of 92 singleton pregnancies. We measured the pulsatility index (PI) of ductus venosus flow velocity waveforms in the recipient twin and performed a retrospective chart analysis for complete maternal blood count before and after the procedure. RESULTS: All variables, except osmolality, IL-6 and AFP were significantly lower in the TTS group. There was a significant positive correlation between PI in the ductus venosus and the amniotic fluid AFP concentrations (r = 0.355; p < 0.001). There was a significant fall in complete maternal blood count after laser therapy (p < 0.001) and a significant correlation between the amount of amniotic fluid drained and the fall of maternal Hb (r = -0.261; p = 0.03) and hematocrit (r = -0.212; p = 0.01). CONCLUSION: Pathophysiologic changes in TTS do not only occur at the inter-twin level of placental vascular anastomoses but also at the materno-fetal level of fluid exchanges. AFP is correlated to the severity of congestive heart failure of the recipient twin.

How can we diagnose and manage twin-twin transfusion syndrome?

Severe mid-trimester twin-twin transfusion syndrome (TTS) complicates about 15% of monochorionic twin pregnancies. If left untreated, the mortality is 80-100%. The pathophysiological prerequisite for the onset of TTS is unequal blood flow via arteriovenous placental anastomoses from the so-called donor to the recipient twin. This can result in hypovolemia, hypotension and oligo- or anuria in the donor, and hypervolemia, hypertension, polyuria and finally heart failure in the recipient. Leading sonographic signs of TTS include severe oligo- or anhydramnios and a small or absent bladder filling in the donor in contrast to polyhydramnios with increased bladder filling in the recipient. Patients might present with clinical symptoms due to massive polyhydramnios. In severe mid-trimester TTS, fetoscopic laser occlusion of the anastomosing vessels on the placental surface under local anaesthesia plus subsequent amniodrainage is the most promising therapeutic option at present. In acute TTS after 26 weeks of gestation, amniodrainage is the therapy of choice. All patients suspected of this high-risk condition should be referred to a specialized fetal medicine centre.