Reduction of right atrial peak systolic velocity in growth-restricted discordant twins

Objective: The objective of this study was to measure blood flow velocity changes through the tricuspid valve in intrauterine growth-restricted twins. Study Design: Discordant twins were evaluated by measurement of tricuspid valve flow velocities. Twin pairs with one intrauterine growth-restricted fetus caused by uteroplacental insufficiency and one appropriately grown fetus were included in the analysis. Fetuses with chromosomal or structural abnormalities and confirmed twin-twin transfusion syndrome were excluded. Eighteen pairs met these criteria. Studentʹs t test was used for comparison of flow velocities. Results: Peak ventricular diastolic flow velocities through the tricuspid valve in the twin with intrauterine growth restriction and the appropriately grown twin were 35.8±4.43 cm/sec and 34.0±6.7 cm/sec, respectively (p=0.35). The atrial peak systolic flow velocity values were 42.1±1.2 and 50.3±1.2, respectively (p=0.049). Conclusions: The velocity of blood flow through the tricuspid valve during atrial systole is lower in growth-restricted twins than in appropriately grown cotwins when growth restriction is caused by uteroplacental insufficiency. Its potential in differentiating discordancy from the other causes remains to be explored.