Recipient umbilical artery elongation (redundancy) in twin-twin transfusion syndrome

Background Chronic hypertension in adults causes arterial lengthening in major arteries, but the effects of early fetal hypertension on the twin-twin transfusion syndrome recipient's vascular architecture remains unknown. Objective We hypothesize that arterial cord redundancy is related to recipient hypertension and subsequent heart failure. Our objectives were to: (1) establish a 3-dimensional color Doppler ultrasound method of measuring umbilical arterial length relative to its corresponding venous segment in the umbilical cord using artery vein angle; (2) compare recipient artery vein angle to gestational age-matched controls; and (3) test the association of artery vein angle with recipient heart failure. Study Design We compared 3 groups prospectively: twin-twin transfusion syndrome pregnancies undergoing fetoscopic laser surgery (preoperatively) and 2 groups of gestational age-matched controls: uncomplicated monochorionic-diamniotic twin pregnancies and healthy singletons. Using a 3-dimensional color-Doppler volume image of 5 cm of cord near the placental insertion, we traced the umbilical artery and vein producing umbilical artery:vein length, (artery vein index) and measured the artery vein angle between umbilical artery and vein. Correlation of artery vein angle to twin-twin transfusion syndrome stage, maximum vertical pocket, umbilical arterial indices, ductus venosus Doppler, and brain natriuretic peptide were performed. We used pulsed-wave and tissue Doppler to measure tissue Doppler velocities and indexed cardiac output and correlated these with artery vein angle. Comparative statistics, including multivariable linear regression, examined the relationship between umbilical arterial Doppler indices and artery vein angle. Results Artery vein angle and artery vein index correlated significantly ( R 2 , 0.86; P P 95th percentile for controls) was measured in 52% recipients. Artery vein angle was higher in twin-twin transfusion syndrome stage 3R vs 1 ( P  = .001). Artery vein angle increased with increasing umbilical arterial pulsatility index ( P P  = .02) after adjusting for gestational age. Interrater agreements to categorize abnormal artery vein angle values was 95% ( P Conclusion Umbilical arterial lengthening occurs in 52% of recipients and is associated with abnormal Doppler flows, low systolic tissue Doppler velocities, reduced cardiac output, and elevated markers of cardiac failure. This may reflect chronicity and severity of hypertension in the recipient fetus. Further research is needed to explore the mechanisms of elongation and long-term implications.