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383: Physiological basis of the Quintero staging system

      Objective

      Twin-twin transfusion syndrome (TTTS) is thought to result from a net flow of blood from the donor to the recipient twin. The Quintero staging system (QSS) is used to classify the heterogeneity and gauge the severity of TTTS and assumes increased severity with advancing Stage.The purpose of this study was to assess the relationship between the flow in the umbilical vein (UV) of the donor twin and Stage.

      Study Design

      UV flow (cc/min) was calculated as: Quv=Au x Vu x 60, where Au and Vu are the area and the blood flow velocity of the UV, respectively. The diameter of the UV was obtained by ultrasound in a perpendicular view of the vein, where as the velocity was obtained in a parallel view. Pulsatile Vu was assessed as the time-average velocity by trace. Measurements were obtained prior to laser surgery in all cases. Logistic regression controlled for Stage, gestational age and estimated fetal weight. Surgeries were approved by the Institutional Review Board and all patients signed informed consent.

      Results

      Three hundred and thirty-two patients underwent pre-operative assessment. Table I shows the median UV flow values by QSS. There was a significant inverse correlation between UV flow and QSS, with a decrease in UV flow from Stage I-III and increased flow in Stage IV. The estimated fetal weight was also significantly correlated, but did not differentiate Stages I-II.
      Table IPre-operative umbilical venous flow in the donor twin by Quintero Stage
      Stage (N)UV flow (cc/min)P value
      I (64)65
      II (95)51.007
      III (149)32.0001
      IV (24)80.0001

      Conclusion

      Umbilical venous flow assessment in the donor twin correlates inversely with disease severity as gauged by the QSS from Stages I-III, differentiating one Stage from another. Improved blood flow to the donor in Stage IV may be associated with increased venous pressure in the recipient twin from congestive heart failure. These hemodynamic findings support the basis of the Quintero Staging system.