Simulated Sequential Laser Therapy of Twin–Twin Transfusion Syndrome

Randomized controlled trial of twin-twin transfusion syndrome laser surgery: the sequential trial

BACKGROUND

Intraoperative blood transfer between twins during laser surgery for twin-twin transfusion syndrome can vary by surgical technique and has been proposed to explain differences in donor twin survival.

OBJECTIVE

This trial compared donor twin survival with 2 laser techniques: the sequential technique, in which the arteriovenous communications from the volume-depleted donor to the volume-overloaded recipient are laser-occluded before those from recipient to donor, and the selective technique, in which the occlusion of the vascular communications is performed in no particular order.

STUDY DESIGN

A single-center, open-label, randomized controlled trial was conducted in which twin-twin transfusion syndrome patients were randomized to sequential vs selective laser surgery. Nested within the trial, a second trial randomized patients with superficial anastomoses (arterioarterial and venovenous) to ablation of these connections first (before ablating the arteriovenous anastomoses) vs last. The primary outcome measure was donor twin survival at birth.

RESULTS

A total of 642 patients were randomized. Overall donor twin survival was similar between the 2 groups (274 of 320 [85.6%] vs 271 of 322 [84.2%]; odds ratio, 1.12 [95% confidence interval, 0.73-1.73]; P=.605). Superficial anastomoses occurred in 177 of 642 cases (27.6%). Donor survival was lower in the superficial anastomosis group vs those with only arteriovenous communications (125 of 177 [70.6%] vs 420 of 465 [90.3%]; adjusted odds ratio, 0.33 [95% confidence interval, 0.20-0.54]; P<.001). In cases with superficial anastomoses, donor survival was independent of the timing of ablation or surgical technique. The postoperative mean middle cerebral artery peak systolic velocity was lower in the sequential vs selective group (1.00±0.30 vs 1.06±0.30 multiples of the median; P=.003). Post hoc analyses showed 2 factors that were associated with poor overall donor twin survival: the presence or absence of donor twin preoperative critical abnormal Doppler parameters and the presence or absence of arterioarterial anastomoses. Depending on these factors, 4 categories of patients resulted: (1) Category 1 (347 of 642 [54%]), no donor twin critical abnormal Doppler + no arterioarterial anastomoses: donor twin survival was 91.2% in the sequential and 93.8% in the selective groups; (2) Category 2 (143 of 642 [22%]), critical abnormal Doppler present + no arterioarterial anastomoses: donor survival was 89.9% vs 75.7%; (3) Category 3 (73 of 642 [11%]), no critical abnormal Doppler + arterioarterial anastomoses present: donor survival was 94.7% vs 74.3%; and (4) Category 4 (79 of 642 [12%]), critical abnormal Doppler present + arterioarterial anastomoses present: donor survival was 47.6% vs 64.9%.

CONCLUSION

Donor twin survival did not differ between the sequential vs selective laser techniques and did not differ if superficial anastomoses were ablated first vs last. The donor twin's postoperative middle cerebral artery peak systolic velocity was improved with the sequential vs the selective approach. Post hoc analyses suggest that donor twin survival may be associated with the choice of laser technique according to high-risk factors. Further study is needed to determine whether using these categories to guide the choice of surgical technique will improve outcomes.

Is the Sequential Laser Technique for Twin-to-Twin Transfusion Syndrome Truly Superior to the Standard Selective Technique? A Meta-Analysis

Background and Objective: To investigate the efficacy of sequential laser coagulation in the treatment of twin-to-twin transfusion syndrome (TTTS). Data Sources: MEDLINE, EMBASE and the Cochrane Library were systematically searched for comparative studies on the efficacy of sequential versus standard selective laser coagulation for TTTS. The primary outcome measure in these studies was survival of at least one twin, both twins and fetal demise. Results: Three cohort studies comparing the selective laser treatment technique (n = 120) versus the sequential technique (n = 224) in 344 monochorionic twin pregnancies were included. Mean survival of at least one twin was 88% in the selective group versus 92% (p = 0.22) in the sequential group. Mean survival of both twins was lower in the selective group (52%) than in the sequential group (75%) (p = 0.002). Donor fetal demise decreased from 34% in the selective to 10% in the sequential group (p < 0.01), and recipient fetal demise decreased from 16 to 7% (p = 0.02). Conclusion: Limited evidence suggests improved double neonatal survival as well as decreased donor and recipient fetal demise with the use of the sequential technique. However, these results are based on small non-randomized studies with evident forms of bias and methodological limitations. A randomized controlled trial to assess the efficacy of sequential laser technique is therefore required.

Placental characteristics in growth-discordant monochorionic twins: a matched case-control study

OBJECTIVE

To compare the placental characteristics in monochorionic (MC) twin pregnancies with and without birth weight discordance (BWD).

METHODS

We performed a matched case-control study to compare the placental characteristics of MC placentas from pregnancies with BWD (≥25%) (n = 47) with a control group of MC placentas without BWD (n = 47), matched for gestational age at birth. Placental sharing, angioarchitecture and diameter of the arterio-arterial (AA) anastomosis were assessed by placental injection with colored dye.

RESULTS

The rate of velamentous cord insertion in MC placentas with and without BWD was 30% (28/94) and 16% (15/94), respectively (p = 0.036). Placental sharing discordance in MC placentas with and without BWD was 36% and 17%, respectively (p < 0.001). The mean diameter of the AA anastomosis in MC placentas with and without BWD was 2.2 mm and 1.8 mm, respectively (p = 0.024).

CONCLUSION

MC placentas from growth-discordant twins are more unequally shared, have a higher rate of velamentous cord insertions and larger diameter of AA anastomosis compared to gestational age matched controls.

New and/or improved aspects of fetal surgery

Open fetal surgery through a wide hysterotomy is no longer a real option for prenatal intervention, but a minimally invasive approach has emerged as treatment for a small number of indications. Endoscopic ablation of placental vessels is the preferred treatment for severe twin-to-twin transfusion syndrome and it may be the only chance to salvage the most severe forms of congenital diaphragmatic hernia. Several other indications are currently under review and may become justified in the future, provided that diagnostic accuracy and patient selection become more accurate. Before invasive fetal intervention becomes widely accepted, however, we need to better define outcome. It is no longer acceptable to express results in terms of survival at birth. Survival at discharge and long-term morbidity must be considered as well.

Fetal heart rate changes associated with sequential selective laser surgery for twin-twin transfusion syndrome

OBJECTIVE

To investigate perioperative changes in fetal heart rate (FHR) associated with sequential vs standard selective laser photocoagulation of communicating vessels for the treatment of twin-twin transfusion syndrome (TTTS).

STUDY DESIGN

Women with TTTS were treated with the intent of using the sequential procedure. Those who failed this treatment were categorized as having undergone the standard procedure. Pre- and postoperative FHR of donor and recipient fetuses were analyzed.

RESULT

Of 98 women, 35 received the standard technique. A postoperative drop in the mean donor FHR was observed in gestations receiving the standard laser, but not in those receiving the sequential technique. In multivariable models that included operative and gestational characteristics, the use of the sequential treatment was associated with improved stability of the FHR of the donor twin.

CONCLUSION

The stability in donor FHR following sequential laser ablation when compared with the standard technique is consistent with improved donor hemodynamics.

Reflectance spectrometry for real-time hemoglobin determination of placental vessels during endoscopic laser surgery for twin-to-twin transfusion syndrome

OBJECTIVE

The objective of the study was to develop a noninvasive technique to determine hemoglobin (Hb) content through spectral analysis of diffusely reflected broadband visible illumination from individual blood vessels during endoscopic fetal surgery for twin-to-twin transfusion syndrome (TTTS).

METHODS

The reflection of an incoming xenon endoscopic light source was captured through a 630-mum-diameter optic fiber coupled to a fixed grating spectrometer (2-nm resolution). A 450- to 700-nm wavelength range was used for analysis. Three data-capturing methods were studied: (1) fixed-image spectrum capture with fiber aimed at (but not touching) center of a vessel, (2) no-touch scanning perpendicular to the vessel and dynamic spectral capture, and (3) dynamic spectral capture and analysis of the reflectance spectra during brief vessel touch.

RESULTS

Eight controls (elective laparoscopic and thoracoscopic operations in children aged 1-17 years) were enrolled. Four vessels were analyzed in each case. The brief-touch technique with intensity peak analysis yielded the most reproducible results between multiple vessels in the same patient. Spectrometry was also applied to 2 TTTS patients. The (anemic) donor and (polycythemic) recipient twin fetuses could be differentiated with good correlation between vessels (arteries and vein) of the same fetus.

CONCLUSIONS

It is possible to differentiate donor from recipient placental vessels by spectral analysis of the reflected light through the endoscope using a noninvasive and real-time method. This may improve the accuracy of endoscopic laser ablation of placental vessels in TTTS and may allow instant endoscopic Hb determination for laparoscopic procedures as well.