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Altered eNOS protein content in uterine and umbilical vessels in an ovine model of fetal growth restriction
S132 SMFM Abstracts West Ballroom, Fontainebleau Hotel 447 ALTERED ENOS PROTEIN CONTENT IN UTERINE AND UMBILICAL VESSELS IN AN OVINE MODEL OF FETAL GROWTH RESTRICTION JUAN ARROYO1, RUSSELL ANTHONY2, THOMAS PARKER2, GATES ROE2, SANTOSH PANDIPATI1, HENRY GALAN1, 1University of Colorado Health Sciences Center, Obstetrics and Gynecology, Denver, Colorado, 2University of Colorado Health Sciences Center, Dept. of Pediatrics, Denver, Colorado OBJECTIVE: Endothelial nitric oxidase synthase (eNOS) is an enzyme known to modulate blood flow and is induced by hypoxia and sheer stress. In an established hyperthermic (HT) ovine model of placental and fetal growth restriction (FGR), we propose to quantify eNOS protein expression in the umbilical vein, umbilical artery and uterine artery of 130 day gestation (dGA) animals. STUDY DESIGN: HT ewes (n=4) were exposed to increased ambient temp for 80 days (starting at 35dGA) and compared to control animals (n=4). At 125 dGA, fetal arterial catheters were placed for blood gas and systemic blood pressure (BP) measurements. Umbilical artery Doppler velocimetry studies were performed just prior to necropsy at 130 dGA. Umbilical artery (UmA) and vein (UmV), and uterine artery (UtA) were subject to western blot analysis (25 mg protein) with an eNOS mAb. eNOS expression was normalized to aˆ-actin. Immunohistochemistry was used to localize eNOS. RESULTS: Compared to controls, 1) HT fetuses and placentae were smaller (p!0.001). 2) a 1.4-fold decrease of eNOS protein in the UtA (see figure), a 2-fold increase of eNOS protein in the UmA and a 1.2-fold increase of eNOS protein in the UmV, 3) HT FGR fetuses showed higher UmA Doppler systolic to diastolic ratios (3.8G0.2 v 3.0G0.3; p!0.009) and systemic BP (44.3G1.7 v 41.1G1.5 mmHg; p!0.03) and 4) HT fetuses had lower O2 saturation (52.2G7.0% v 33.1G11.0% p!0.008) and paO2 (18.9G1.5 mmHg v 13.9G1.9 mmHg; p!0.002). eNOS localized to the endothelium of all vessels.
Uterine Artery eNOS Content by Groups CONCLUSION: Consistent with lower uterine blood flow in this model, eNOS protein content is reduced in the uterine artery of FGR ewes. In contrast, eNOS protein content is increased in the umbilical artery and vein of the FGR fetus, which may result from fetal hypoxia and increased shear stress as related to increased systemic BP and UmA Doppler findings. Supported by NIH grant R01 HL071990-01A1.
448 FETOSCOPIC LASER ABLATION OF PLACENTAL VASCULAR ANASTOMOSES CORRECTS UMBILICAL VENOUS VOLUME FLOW ABNORMALITIES RESPONSIBLE FOR TWINTWIN TRANSFUSION SYNDROME AHMET BASCHAT1, MICHAEL TCHIRIKOV2, AGNES HUBER2, KURT HECHER3, 1University of Maryland at Baltimore, Obstetrics, Gynecology and Reproductive Sciences, Baltimore, Maryland, 2Universita¨tsklinikum Hamburg-Eppendorf, Hamburg, Germany, 3Universita¨tsklinikum Hamburg-Eppendorf, Obstetrics & Prenatal Medicine, Hamburg, Germany OBJECTIVE: Unbalanced distribution of umbilical venous volume flow (UVVF) through placental vascular anastomoses has been proposed as the primary mechanism for development of twin-twin transfusion syndrome (TTTS). Fetoscopic laser occlusion (FLOC) of placental vascular anastomoses aims to terminate this process. We sought to determine the impact of FLOC on umbilical venous volume flow (UVVF) in TTTS. STUDY DESIGN: Patients with severe TTTS undergoing FLOC had serial Doppler measurements of UVVF performed in the straight portion of the intraabdominal umbilical vein by a standardized technique. Serial changes in UVVF, intertwin differences in UVVF between twin pairs at 24, and 48 hours after FLOC were examined. Serial changes in volume flow were related to time after procedure, number of anastomoses, umbilical and venous Doppler status and bladder filling. RESULTS: Thirty-five patients were studied. Prior to FLOC the magnitude of UVVF was significantly higher in the recipients (64 vs. 47 ml/min p!0.005). 24 hours after FLOC the UVVF in the recipient group was not significantly changed but in donors increased to a median of 69 ml/min. These findings remained unchanged at 48 hours (p!0.05). Accordingly, intertwin difference in UVVF decreased from 19.5 ml/min to 8.6 ml/min by 48 hours (p!0.005).
The changes in volume flow were not related to any Doppler parameters or number of anastomoses. On day 2 after FLOC UVVF was higher in donor twins with new evidence of bladder filling (73 vs. 43 ml/min, p!0.005). CONCLUSION: Fetoscopic laser ablation of placental vascular anastomoses corrects intertwin differences in umbilical venous volume flow observed in severe TTTS. The predominant effect observed initially is normalization of volume flow in the donor twin. Enhanced bladder filling observed in these circumstances provides a clinicial correlate for successful correction of intravscular volume status. Impacts on the recipient are likely to be more gradual and therefore not detected in the time frame studied. 449 INTERTWIN DIFFERENCES IN UMBILICAL VENOUS VOLUME FLOW IN TWIN TO TWIN TRANSFUSION SYNDROME (TTTS) AHMET BASCHAT1, MICHAEL TCHIRIKOV2, AGNES HUBER2, KURT HECHER3, 1University of Maryland at Baltimore, Obstetrics, Gynecology and Reproductive Sciences, Baltimore, Maryland, 2Universita¨tsklinikum Hamburg-Eppendorf, Hamburg, Germany, 3Universita¨tsklinikum Hamburg-Eppendorf, Obstetrics and Prenatal Medicine, Hamburg, Germany OBJECTIVE: Placental vascular anastomoses in monochorionic multiple gestations permit intertwin transfer of blood volume. TTTS is thought to result from unbalanced transfer of blood volume. As there is little information on the dynamics of this mechanism we sought to evaluate relationships between fetal umbilical venous volume flow (UVVF) and TTTS severity. STUDY DESIGN: Fetal anatomy, biometry, amniotic fluid (AF) pocket, umbilical artery (UA) and ductus venosus (DV) Doppler were evaluated in 57 TTTS pregnancies. Standardized Doppler measurement of UVVF was obtained from the straight portion of the intraabdominal umbilical vein. Intertwin differences in UVVF were related to fetal weight, Quintero stage, UA/DV Dopplers and AF. RESULTS: In recipients median UVVF and UVVF/abdominal circumference were higher than in donors (66 vs. 45 ml/min and 0.33 vs. 0.25 respectively, all p!0.001). In both twins advancing Quintero stage was associated with a decline in all UVVF parameters (p!0.05). Due to a disproportional effect on the donor intertwin UVVF difference increased from 28 ml/min in stages 1/2 to 58 ml/min in stages 3/4 (p!0.007). This difference in UVVF correlated with UA and DV blood flow resistance (Pearson’s 0.5 and 0.55, p!0.0005). Logistic regression revealed that placental blood flow resistance was the primary determinant of intertwin difference in UVVF (r2 0.22, p!0.05). CONCLUSION: In TTTS umbilical venous volume flow is significantly higher in the recipient. In early stages magnitude of UVVF is greater in both twins but intertwin differences are smaller. With progression to cardiovascular compromise magnitude of UVVF decreases while intertwin differences increase. Placental territory as indicated by umbilical artery Doppler is the main contributor to this effect. As TTTS severity advances donor twins experiences significant decrease in venous flow while the magnitude of UVVF necessary to trigger cardiovascular decompensation in the recipient becomes smaller. Further study of these dynamics is warranted to refine diagnostic and prognostic assessment. 450 SURVIVAL AFTER LASER SURGERY FOR TTTS: WHEN ARE THEY OUT OF THE FRANCOIS I. LUKS2, MARSHALL CARPENTER1, WOODS? STEPHEN CARR1, LIESBETH LEWI3, ROLAND DEVLIEGER4, JACQUES LANI3, JAN A. DEPREST3, 1Women & Infants’ Hospital, Maternal-Fetal Medicine, Providence, Rhode Island, 2Brown University, Pediatric Surgery, Providence, Rhode Island, 3University Hospital Gasthuisberg, Leuven, Belgium, 4Centre for Surgical Technologies, Leuven, Belgium OBJECTIVE: To examine survival curves in twins suffering from TTTS following laser ablation of chorioangiopagus vessels according to stage of disease. STUDY DESIGN: A retrospective cohort study from two centers on a consecutive series of 157 sets of MC/DA twins (17 stage 1, 54 stage 2, 66 stage 3, 18 stage 4) who underwent laser ablation (LA) of placental vessels. Time-toIUFD following laser ablation was analyzed using Kaplan-Meier curves. RESULTS: Mortality in the first five days following laser surgery was 10.5% and was equally distributed between donor and recipient. Overall, recipient twins had a 10% survival advantage over donor twins. Survival was similar for Stage 1, 2, and 4 (75-80%), compared with 55% for Stage 3. Ninety percent of all deaths occurred within 35 days postoperatively.
CONCLUSION: Actuarial survival curves for TTTS suggest a greater burden on donor than on recipient twins. Furthermore, the current staging schema does not accurately reflect post-LA mortality risk. The unexpected higher mortaility in stage 3 may reflect the possible acute progression of the disorder in this group or an adverse effect of LA in an as-yet unknown subgroup with stage 3. These data suggest that the natural history of this disorder and the impact of LA treatment in more narrowly specified subgroups require further investigation.
Uterine Artery eNOS Content by Groups CONCLUSION: Consistent with lower uterine blood flow in this model, eNOS protein content is reduced in the uterine artery of FGR ewes. In contrast, eNOS protein content is increased in the umbilical artery and vein of the FGR fetus, which may result from fetal hypoxia and increased shear stress as related to increased systemic BP and UmA Doppler findings. Supported by NIH grant R01 HL071990-01A1.
448 FETOSCOPIC LASER ABLATION OF PLACENTAL VASCULAR ANASTOMOSES CORRECTS UMBILICAL VENOUS VOLUME FLOW ABNORMALITIES RESPONSIBLE FOR TWINTWIN TRANSFUSION SYNDROME AHMET BASCHAT1, MICHAEL TCHIRIKOV2, AGNES HUBER2, KURT HECHER3, 1University of Maryland at Baltimore, Obstetrics, Gynecology and Reproductive Sciences, Baltimore, Maryland, 2Universita¨tsklinikum Hamburg-Eppendorf, Hamburg, Germany, 3Universita¨tsklinikum Hamburg-Eppendorf, Obstetrics & Prenatal Medicine, Hamburg, Germany OBJECTIVE: Unbalanced distribution of umbilical venous volume flow (UVVF) through placental vascular anastomoses has been proposed as the primary mechanism for development of twin-twin transfusion syndrome (TTTS). Fetoscopic laser occlusion (FLOC) of placental vascular anastomoses aims to terminate this process. We sought to determine the impact of FLOC on umbilical venous volume flow (UVVF) in TTTS. STUDY DESIGN: Patients with severe TTTS undergoing FLOC had serial Doppler measurements of UVVF performed in the straight portion of the intraabdominal umbilical vein by a standardized technique. Serial changes in UVVF, intertwin differences in UVVF between twin pairs at 24, and 48 hours after FLOC were examined. Serial changes in volume flow were related to time after procedure, number of anastomoses, umbilical and venous Doppler status and bladder filling. RESULTS: Thirty-five patients were studied. Prior to FLOC the magnitude of UVVF was significantly higher in the recipients (64 vs. 47 ml/min p!0.005). 24 hours after FLOC the UVVF in the recipient group was not significantly changed but in donors increased to a median of 69 ml/min. These findings remained unchanged at 48 hours (p!0.05). Accordingly, intertwin difference in UVVF decreased from 19.5 ml/min to 8.6 ml/min by 48 hours (p!0.005).
The changes in volume flow were not related to any Doppler parameters or number of anastomoses. On day 2 after FLOC UVVF was higher in donor twins with new evidence of bladder filling (73 vs. 43 ml/min, p!0.005). CONCLUSION: Fetoscopic laser ablation of placental vascular anastomoses corrects intertwin differences in umbilical venous volume flow observed in severe TTTS. The predominant effect observed initially is normalization of volume flow in the donor twin. Enhanced bladder filling observed in these circumstances provides a clinicial correlate for successful correction of intravscular volume status. Impacts on the recipient are likely to be more gradual and therefore not detected in the time frame studied. 449 INTERTWIN DIFFERENCES IN UMBILICAL VENOUS VOLUME FLOW IN TWIN TO TWIN TRANSFUSION SYNDROME (TTTS) AHMET BASCHAT1, MICHAEL TCHIRIKOV2, AGNES HUBER2, KURT HECHER3, 1University of Maryland at Baltimore, Obstetrics, Gynecology and Reproductive Sciences, Baltimore, Maryland, 2Universita¨tsklinikum Hamburg-Eppendorf, Hamburg, Germany, 3Universita¨tsklinikum Hamburg-Eppendorf, Obstetrics and Prenatal Medicine, Hamburg, Germany OBJECTIVE: Placental vascular anastomoses in monochorionic multiple gestations permit intertwin transfer of blood volume. TTTS is thought to result from unbalanced transfer of blood volume. As there is little information on the dynamics of this mechanism we sought to evaluate relationships between fetal umbilical venous volume flow (UVVF) and TTTS severity. STUDY DESIGN: Fetal anatomy, biometry, amniotic fluid (AF) pocket, umbilical artery (UA) and ductus venosus (DV) Doppler were evaluated in 57 TTTS pregnancies. Standardized Doppler measurement of UVVF was obtained from the straight portion of the intraabdominal umbilical vein. Intertwin differences in UVVF were related to fetal weight, Quintero stage, UA/DV Dopplers and AF. RESULTS: In recipients median UVVF and UVVF/abdominal circumference were higher than in donors (66 vs. 45 ml/min and 0.33 vs. 0.25 respectively, all p!0.001). In both twins advancing Quintero stage was associated with a decline in all UVVF parameters (p!0.05). Due to a disproportional effect on the donor intertwin UVVF difference increased from 28 ml/min in stages 1/2 to 58 ml/min in stages 3/4 (p!0.007). This difference in UVVF correlated with UA and DV blood flow resistance (Pearson’s 0.5 and 0.55, p!0.0005). Logistic regression revealed that placental blood flow resistance was the primary determinant of intertwin difference in UVVF (r2 0.22, p!0.05). CONCLUSION: In TTTS umbilical venous volume flow is significantly higher in the recipient. In early stages magnitude of UVVF is greater in both twins but intertwin differences are smaller. With progression to cardiovascular compromise magnitude of UVVF decreases while intertwin differences increase. Placental territory as indicated by umbilical artery Doppler is the main contributor to this effect. As TTTS severity advances donor twins experiences significant decrease in venous flow while the magnitude of UVVF necessary to trigger cardiovascular decompensation in the recipient becomes smaller. Further study of these dynamics is warranted to refine diagnostic and prognostic assessment. 450 SURVIVAL AFTER LASER SURGERY FOR TTTS: WHEN ARE THEY OUT OF THE FRANCOIS I. LUKS2, MARSHALL CARPENTER1, WOODS? STEPHEN CARR1, LIESBETH LEWI3, ROLAND DEVLIEGER4, JACQUES LANI3, JAN A. DEPREST3, 1Women & Infants’ Hospital, Maternal-Fetal Medicine, Providence, Rhode Island, 2Brown University, Pediatric Surgery, Providence, Rhode Island, 3University Hospital Gasthuisberg, Leuven, Belgium, 4Centre for Surgical Technologies, Leuven, Belgium OBJECTIVE: To examine survival curves in twins suffering from TTTS following laser ablation of chorioangiopagus vessels according to stage of disease. STUDY DESIGN: A retrospective cohort study from two centers on a consecutive series of 157 sets of MC/DA twins (17 stage 1, 54 stage 2, 66 stage 3, 18 stage 4) who underwent laser ablation (LA) of placental vessels. Time-toIUFD following laser ablation was analyzed using Kaplan-Meier curves. RESULTS: Mortality in the first five days following laser surgery was 10.5% and was equally distributed between donor and recipient. Overall, recipient twins had a 10% survival advantage over donor twins. Survival was similar for Stage 1, 2, and 4 (75-80%), compared with 55% for Stage 3. Ninety percent of all deaths occurred within 35 days postoperatively.
CONCLUSION: Actuarial survival curves for TTTS suggest a greater burden on donor than on recipient twins. Furthermore, the current staging schema does not accurately reflect post-LA mortality risk. The unexpected higher mortaility in stage 3 may reflect the possible acute progression of the disorder in this group or an adverse effect of LA in an as-yet unknown subgroup with stage 3. These data suggest that the natural history of this disorder and the impact of LA treatment in more narrowly specified subgroups require further investigation.