TTTS. Doppler
Doppler investigations of the arterial vessels and ductus venosus, inferior vena cava, right hepatic vein, tricuspid, and mitral ventricular inflow were performed in both fetuses. The most significant findings on the arterial side were an increased mean umbilical artery pulsatility index and a decreased mean value for aortic blood flow velocity in both groups of fetuses.
Five recipients and 4 donors had absence or reversal of blood flow during atrial contraction in the ductus venosus. All these fetuses showed pulsations in the umbilical vein. Tricuspid regurgitation was present in 8 recipients. Absence or reversal of end-diastolic velocities in the umbilical artery was found in 4 donors. The recipient’s circulation showed characteristics of congestive heart failure due to hypervolemia.
Alterations in the donor’s circulation were consistent with decreased venous return due to hypovolemia and increased cardiac afterload due to increased placental resistance. Intra-amniotic Doppler measurements were performed by Nakata et al.33 A 2 mm probe was introduced in the amniotic cavity and Doppler measurements were performed in the anastomoses, directly visualized by the endoscope. Two cases were included in this study and the flow was calculated by the diameter of the vessel by Doppler and the mean velocity.
The net flow in both cases was from recipient to donor. Recently, venous flow measurements have been introduced in the evaluation of TTTS. The umbilical vein flow calculated as a flow per fetal weight has been measured in recipients and donors before and after laser in 32 cases, with a significative difference between both twins and an increase of 50% in donors after laser.34 A later report confirmed the findings.
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