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Keywords:

  • Doppler;
  • MPI;
  • repeatability;
  • Tei index

Abstract

Objective

To assess reproducibility of constituent time intervals measured by pulsed Doppler echocardiography for calculation of the right and left fetal myocardial performance indices (MPIs).

Methods

This was a prospective study of 30 normal singleton pregnancies (19–36 weeks). In each, five different time intervals were measured from the Doppler waveform and four repeated measures were taken for each time interval. Three were from the left heart: isovolumetric contraction time (ICT), isovolumetric relaxation time (IRT) and ejection time (ET); two were from the right heart: ‘a-interval’ and ‘b-interval’. The left and right modified MPIs (Mod-MPIs) generated by these constituent time intervals were also evaluated. Two operators evaluated the reproducibility of all measures.

Results

There was generally good intra- and interobserver reproducibility for all time intervals and resultant Mod-MPIs: ICT, range, 19–43 ms with intraclass correlation coefficient (ICC), 0.91 (95% CI, 0.85–0.95); ET, range, 160–184.8 ms with ICC, 0.90 (95% CI, 0.84–0.95); IRT, range, 35.8–48.5 ms with ICC, 0.67 (95% CI, 0.52–0.81); a-interval, range 208–265 ms with ICC, 0.89 (95% CI, 0.82–0.94); b-interval, range, 163.1–188.3 ms with ICC, 0.82 (95% CI, 0.71–0.90); left Mod-MPI, range, 0.33–0.48 with ICC, 0.84 (95% CI, 0.74–0.91); right Mod-MPI, range, 0.21–0.49 with ICC, 0.82 (95% CI, 0.71–0.90). The 95% limits of agreement showed no statistically significant difference in measurements between the two examiners for all time intervals.

Conclusion

This is the first study to evaluate the reproducibility of the component time intervals of both right and left fetal Mod-MPIs in the second and third trimesters and supports the reproducibility of fetal functional cardiac assessment. The IRT is the main source of variation for the left Mod-MPI so should be the focus of further investigation. Even using two separate pulsed-wave Doppler gates and therefore separate cardiac cycles, the right Mod-MPI is reproducible. Copyright © 2012 ISUOG. Published by John Wiley & Sons, Ltd.