The surgical method of laser therapy has undergone several modifications to become what is successfully used today. The first technique lasered all vessels that crossed the intertwin dividing membranes.16,17
Subsequently, Quintero et al developed the selective technique (selective laser photocoagulation of communicating vessels, or SLPCV), which selectively ablates only the vascular communications and does not require location of the dividing membrane.18
Ablation of all vascular anastomoses after SLPCV essentially transforms a monochorionic twin pregnancy into a “functional” dichorionic twin pregnancy, with no further exchange of blood between the fetuses.31
SLPCV is associated with at least one twin surviving in approximately 88% to 91% of cases32,33
and a median gestational age at delivery of 33 6/7 weeks.34
A randomized controlled trial conducted in Europe compared serial amniocentesis versus
The trial showed approximately a 4-week difference in pregnancy duration between the groups (29 vs 33 weeks, amniocentesis vs laser, respectively, P
and the amniocentesis group had significantly higher neurological complications (14% vs 6%, P
= .02). This difference persisted at the 6-month follow-up evaluation.35
Although, in retrospect, not all laser-treated patients underwent SLPCV (in fact, most underwent a nonselective technique), laser therapy was still superior to amniocentesis.
A third-generation laser technique has been reported,33
which involves lasering the arteriovenous anastomoses in a specific sequence (sequential laser photocoagulation of communicating vessels, or SQLPCV), such that the AV anastomoses from the donor to the recipient are lasered first, followed by the remaining communications.33
By performing the laser ablation in this sequential fashion, the donor twin is prevented from losing further blood into the recipient twin intraoperatively. This may be significant, even if the laser step of the procedure takes only 10 to 15 minutes. Furthermore, during such time, the donor twin receives an intraoperative transfusion from the recipient twin until all the AVRD anastomoses are ablated. In the original study describing the technique, SQLPCV resulted in increased dual survival rate compared to standard SLPCV (74% vs 57%, P
= .005). The rate of at least one twin survivor was similar (91% vs 88%).33
Although a sequential technique may not be required in all cases, it could be indicated in patients where the condition of the donor twin would be most compromised. The merits of performing SQLPCV versus SLPCV are being investigated through a randomized clinical trial conducted by the USFetus group36
Complications of Laser Therapy
The definitive treatment of TTTS requires that all placental vascular anastomoses be occluded. Incomplete (missed anastomoses) or inadequate (sublasered) laser ablation of the anastomoses leaves patent placental vascular anastomoses, which allow the fetuses to continue to exchange blood37
). Residual patent vascular anastomoses (RPVAS) may result in persistent TTTS (the condition continues) or reverse TTTS (the roles of the twins are reversed, such that the original donor becomes the new recipient, and the original recipient becomes the new donor). Persistent TTTS results from remaining AVDR anastomoses, whereas reverse TTTS results from remaining AVRDs. If both AVDRs and AVRDs remain patent, persistent or reverse TTTS may occur depending on the direction of the net exchange of blood between the fetuses.
Incomplete or inadequate laser therapy may also result in another condition, twin anemia-polycythemia sequence (TAPS), defined below and described in Chapter 5
. If the demise of one twin occurs after surgery, incomplete or inadequate laser therapy may result in anemia or demise of the co-twin from postmortem fetofetal hemorrhage through the patent placental vascular anastomoses.
Failed laser surgery is defined as persistent or reverse TTTS or TAPS. Suspected anemia of a surviving twin after demise of the co-twin, by assessment of the peak systolic velocity of the middle
cerebral artery (MCA-PSV), may also be due to RPAVs, although it may reflect the sequence of how the anastomoses were lasered. Dual fetal demise with postmortem demonstration of RPVASs is considered failed laser therapy. The rate of failed laser therapy varies significantly between 1% and 33% (Tables 24.3
In view of the relatively high incidence of RPVAS seen by some groups, some authors proposed “connecting the dots” between photocoagulated areas on the surface of the placenta.49
The premise behind this idea was that, by lasering spaces between laser-ablated placental vascular anastomoses, such “blind lasering” would capture “anastomoses” that would have been presumably missed (“not visible”).50
The resulting surgical technique of lasering healthy interanastomotic areas of the placenta has been called the “the Solomon technique”49
in reference to the biblical passage where, in order to resolve a dispute between two alleging mothers of the same child, King Solomon proposed to cut the baby in half (1 Kings 3:16-28, NIV). The analogy, therefore, is that by lasering the areas of the placenta between endoscopically identified and laser-ablated vascular anastomoses, the placenta would be “cut in half.”
To test whether the Solomon technique could indeed reduce the rate of RPVAS, an open-label randomized clinical trial was conducted in Europe (the Solomon trial) comparing the Solomon technique versus the “standard” technique (SLPCV).41,42,43
The study showed a decreased rate of persistent or reverse TTTS (2/137, 1% vs 9/135, 7%, Solomon vs “standard”, respectively, P
= .03) and of TAPS (4/137, 2.9% vs 21/135, 15.5%, Solomon vs “standard”, respectively, P
= <.001). Interestingly, the actual rate of RPVAS was no different between the two techniques (14/74, 19% vs 23/77, 29.8%, Solomon vs “standard,” respectively, P
= .12). Although the primary outcome of the study was no different between the groups, the authors concluded that the Solomon technique was superior to the “standard” technique. Two additional observational studies comparing the Solomon technique with the selective technique also appeared to show favorable results with the former technique.47,48
However, the superiority of the Solomon technique to the SLPCV technique has not been proven.
shows the rate of residual patent placental vascular anastomoses reported by the different groups using either the Quintero selective (SLPCV) technique (ie, the “standard” approach) or the Solomon technique. As can be seen, the rate of RPVAS is lowest using the Quintero SLPCV. Table 24.4
shows that the Quintero SLPCV technique is also associated with a lower rate of persistent or reverse TTTS than that of the “standard” technique in the Solomon trial, and the “selective technique” of other authors and that the Solomon technique in all studies achieves the same rate of persistent or reverse TTTS than that reported with the Quintero SLPCV technique. Given that the Solomon technique is still associated with approximately 20% of RPVAS, the initial rationale for the technique, ie, to reduce the high rate of RPVAS, does not appear to hold. Furthermore, since the proponents of the Solomon technique have suggested that most missed anastomoses are located in the margins of the placenta,46
lasering inexistent placental vascular anastomoses in otherwise healthy placental tissue between vascular anastomoses within the main body of the placenta is incongruent with the rationale (Table 24.5
; Figure 24.1
). Altogether, the Solomon technique would seem to represent a backward step in the ability to correctly identify all of the placental vascular anastomoses, by accepting the unproven theory of the presence of nonvisible placental vascular anastomoses in otherwise
healthy-appearing placenta. Alternatively, we have shown that all
of the placental vascular anastomoses can be clearly identified on the surface of the placenta. Stated differently, the use of the “Solomon technique” may simply represent an attempt to achieve similar results as those that can be obtained with the performance of the Quintero SLPCV technique, rather than a real advantage over the SLPCV technique, at the expense of lasering healthy placental tissue.
Table 24.4 Reported Incidence of Clinical Outcomes After Laser Therapy Reflecting Residual Patent Placental Vascular Anastomoses
Reverse or Persistent TTTS
TTTS, twin-twin transfusion syndrome.
Comparisons made relative to the lowest reported rate.
Table 24.5 Principles and Results of the Use of the Solomon Technique to Identify and Ablate all Placental Vascular Anastomoses in Twin-Twin Transfusion Syndrome
Purpose of the Surgery
Purported Location of the Residual Patent Placental Vascular Anastomoses
Actual Location of the Additional Laser Ablations
Rate of Residual Patent Placental Vascular Anastomoses41-43
Rate of Residual Patent Placental Vascular Anastomoses (USFetus Group)37-39
Decrease the rate of residual patent placental vascular anastomoses after laser therapy
Mostly on the margins of the placenta
Within the body of the placenta, between endoscopically identified vascular anastomoses
30% (“Standard”) vs 19% (Solomon)
P > .05
P < .05 relative to Solomon technique
Successful ablation of the placental vascular anastomoses assumes that the surgeon can conduct an adequate assessment of the placenta as well as occlude all of the offending anastomoses. Adequate placental assessment refers to the ability of the surgeon to survey the entire vascular equator. For example, in a subanalysis of the Solomon trial, the authors reported that they were able to adequately assess the placenta in only 65 out of 74 patients in the Solomon group (87%) and in only 69 out of 77 (89%) in the “standard” group,41,42,43
with inability to assess the placenta in 10%. If the placenta cannot be adequately assessed, this can result in missed anastomoses and thus an increased likelihood for persistent or reverse TTTS. In contrast, we have shown consistently the ability to assess the placenta adequately in over 99% of the patients.34
Once all of the anastomoses have been identified, the next surgical competency benchmark refers to the ability of the surgeon to ablate the vascular anastomoses without including nonanastomotic vessels.34,44,51
For this, the surgeon must be able to
adapt to the different clinical scenarios, including placental location, maternal habitus, and other challenging conditions.
Figure 24.1 A, Selective laser photocoagulation of communicating vessels (SLPCV). All of the anastomoses are photocoagulated, regardless of their location relative to the dividing membrane, while sparing nonanastomotic vessels. Rate of residual patent placental vascular anastomoses: 3.5% to 5%.37,44 B, Solomon modification of the SLPCV technique. The fetal surface of the placenta between endoscopically identified anastomoses is also lasered to occlude “anastomoses” not visible by the endoscope. Rate of residual patent vascular anastomoses: 20%.41,42,43
Accuracy of Laser Therapy
Theoretically, one could combine the rate of adequate placental assessment and of selective laser surgery with the rate of either residual patent placental vascular anastomoses (when available) and the rate of persistent or reverse TTTS to determine how accurate the laser surgery is being performed at a given center or by a given surgeon. Accuracy of SLPCV could thus be defined as:
AccSLPCV = QSI × (1-RPPVA) × (1-PRTTTS)
where, AccSLPCV is the accuracy in performing SLPCV, QSI is the rate of Quintero selectively performed surgeries, RPPVA is the rate of residual patent placental vascular anastomoses (when available), and PRTTTS is the rate of persistent or reverse TTTS. Table 24.6
shows such a theoretical calculation and its use to compare outcomes of different reports.
Significant strides have been made both in establishing the scientific merit of using laser therapy to ablate the placental vascular anastomoses present in TTTS35
as well as in the various steps, techniques, and other technical aspects that allow for such a therapy.
The development of the selective technique represented an important historical step in the surgical treatment of TTTS. A properly performed SLPCV technique is associated with the highest rate of clinical success and with the lowest rate of failed therapy either by surgical pathology or clinical criteria.51
Selective feticide via UCO should be the exception rather than the rule for severe cases of TTTS, and should not be performed to compensate for physician or surgical center limitations. Improvements in surgical competence, equipment, and other ancillary technology should continue to remain among the objectives of caregivers in this field.
Table 24.6 Accuracy of Laser Surgery for Twin-Twin Transfusion Syndrome (TTTS)
Rate of Selectively Performed Surgeries
1-Rate of Residual Patent Placental Vascular Anastomoses
1-Rate of Persistent/Reverse TTTS
Accuracy of SLPCV
SLPCV, selective laser photocoagulation of communicating vessels.
1- rate of adverse outcome, rate of success.