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. Student's 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.