Doppler assessment of the effect of umbilical-cord ligation of acardiac twins

OBJECTIVE: We have proposed fetoscopic umbilical-cord ligation (UCI.) as a management alternative for acardiac twins. We wished to study the hemodynamic effects of this technique on the surviving twin. STUDY DESIGN: Pulsed Doppler of the umbilical artery, middle cerebral artery and thoracic aorta was performed on the pump twin before and after L'CL. Standard arterial Doppler parameters were calculated. The ductus venosus (DV), right hepatic vein, the inferior vena cava (IVC) and the umbilical vein were also assessed. The systolic and diastolic peak velocities of these vessels were calculated. The peak velocity of the atrial contraction waveform (ACPV), the velocity-time integral of forward flow of the IVC (VTirVC) and of the atrial contraction waveform (VTIAC) were also calculated. The IVC pre-load index was calculated as ACPV/peak velocity during systole. Three consecutive uniform waveforms in the absence of fetal breathing, arrhythmia or movement were measured and averaged. Each case served as its own control. Post-operative assessment was performed within 1.2 days of the procedure. Information was considered complete if pre-and post-operative data was available. Differences were analyzed with paired Student's T-test. RESULTS: Ten patients underwent UCL, but complete data was only available in 5. Four of 5 studied fetuses survived. There were no significant post-operative differences in the Doppler parameters of the arterial vessels. However, subjective changes were apparent, with easy detection of peripheral arteries (tibial, radial, pedial). A significant post-operative decrease of the ACPV and the VTIAC was noted (p<0.01 ). A mean reduction of 38.2% in the preload index of the IVC was observed (range 13%-51%), (p=0.009). CONCLUSIONS: UCL is not associated with increased impedance to blood flow in the surviving twin. Subjective arterial findings may indicate post-operative redistribution of blood, with a net zero effect on standard arterial Doppler parameters. Doppler assessment of the venous system shows clear post-operative changes. Pulsed Doppler interrogation of the IVC may have diagnostic value to estimate the excess volume originally handled by the pump twin. Clinical and Doppler data suggest that UCL is well tolerated by the surviving fetus.