What is the definition of pulsatile umbilical venous flow in twin-twin transfusion syndrome?

OBJECTIVE: The aim of the study was to derive an objective definition of pulsatile umbilical venous flow ( PUVF). STUDY DESIGN: Pulsed Doppler waveform analysis of the umbilical vein was performed in stages III and IV twin-twin transfusion syndrome ( TTTS) patients. In patients with PUVF, the umbilical vein maximum ( Vmax) and the umbilical vein minimum velocity ( Vmin) and the resistance index for the umbilical vein ( UVRI) = ( 100 x [ Vmax - Vmin]/Vmax) were assessed. RESULTS: PUVF was noted in 130 of 226 stages III and IV TTTS patients. Digital images were available for analysis in 65 of 130 patients ( 50%). The minimum UVRI associated with PUVF was 16% for stages III and IV TTTS. There was a trend for increasing UVRI with stage ( P = .052). Stage IV patients were more likely to have an UVRI greater than 30% ( P = .02). CONCLUSION: PUVF can be defined as an UVRI greater than 15%. A scale definition of PUVF may further facilitate assessment of the degree of fetal hemodynamic compromise.