(601) Confirmation of the physiological principles of the sequential laser technique for twin-twin transfusion syndrome

Objective: To assess changes in middle cerebral artery peak systolic velocity (MCA-PSV) after sequential vs selective laser surgery for twin-twin transfusion syndrome (TTTS).

Study Design: This is a post hoc analysis of data from the Sequential Trial, a randomized controlled trial (RCT) that compared laser techniques for TTTS patients between 18-26 weeks of gestation. Patients received either the original (selective) or a modified selective (sequential) laser surgery, in which arteriovenous (AV) anastomoses with unidirectional blood flow from donor to recipient are laser-ablated first, followed by ablation of AV anastomoses from recipient to donor that should allow for a net intraoperative blood transfer from the hypervolemic recipient to the hypovolemic donor twin. We compared the difference (Delta) in donor MCA-PSV multiples of the median (MoM) (postoperative minus preoperative) by surgical technique. Because anemia is associated with a higher MCA-PSV, a negative Delta is consistent with an increased blood volume.

Results: In the 606 study patients, the mean (SD) Delta MCA-PSV MoM for the donor twin was -0.067 (0.301) (P< .0001) for the sequential and -0.017 (0.288) (P=.4186) for the selective techniques, with P< .0001 for the technique comparison. Based on donor critical abnormal Dopplers (CAD) and arterioarterial (AA) anastomoses, 4 risk Categories with donor survival rates were established (Figure). Mean (SD) Deltas for the sequential vs selective procedures are shown by Category in the Table. Linear regression for Delta, controlling for the risk groups, yielded a coefficient for the sequential vs selective techniques of -0.079 (0.024 SE), P=.0009.

Conclusion: Overall, patients receiving the sequential vs the selective technique had a greater drop in the mean donor MCA-PSV MoM, suggesting that the sequential technique facilitated an intraoperative net blood transfusion to the donor. This benefit was apparent in all risk groups except Category 4, which had poor donor survival. Further study is needed to understand and optimize outcomes of Category 4 patients.