Fetal cardiac tissue doppler: Effect of the doppler angle on time intervals

Purpose: To examine the influence of doppler insonation angle on fetal cardiac time intervals.

Material and methods: Pulsed Tissue Doppler measurements were performed in the right subvalvular ventricular myocardium and measured cardiac time intervals were used to calculate TD-Tei Index. We retrospectively examined 215 fetal cardiac tissue doppler measurements with regard to the doppler insonation angle using the intraventricular septum as reference. In 196 cases (91%) we were able to measure the angle of insonation.

Results: In apical four chamber view we found a positive correlation between lateral deviation of the insonation angle for Tei Index ((IVC + IVR)/ET) and isovolumic times (IVC and IVR). We found a negative correlation between insonation angle and ejection time (ET) albeit without statistical significance: Pearson's r = 0.138 and sig (2-tailed)= 0.054.

Conclusion: Myocardial movement is three dimensional. Using doppler one can measure a one-dimensional vector derived from a three-dimensional movement. To the best of our knowledge this is the first study to examine the angle dependency on Tei index measurements using pulsed tissue doppler in a prenatal setting. We could demonstrate an angle dependency that has an influence on measured Tei indices, however without reaching statistical significance.