Reference values for left and right ventricular systolic-to-diastolic duration ratio (SDR) found using both spectral and tissue Doppler of fetal heart between 20 and 36+6 weeks of gestation.

Purpose: To establish reference values for the systolic-to-diastolic duration ratio (SDR) of the left ventricle (LV) using spectral Doppler, as well as for the SDR' of the interventricular septum (SEP), LV, and right ventricles (RV) using tissue Doppler of the fetal heart.

Method: This prospective and cross-sectional study evaluated 374 low-risk singleton pregnancies from 20 to 36 + 6 weeks of gestation. The ventricular filling time (FT) was obtained from LV inflow using spectral Doppler. Tissue Doppler was used to assess the FT of each ventricle by placing the cursor at the atrioventricular junction marked by the mitral and tricuspid valves, respectively. SDR was calculated as the sum of the isovolumic contraction time (ICT) and the ejection time (ET) divided by the sum of the isovolumic relaxation time (IRT) and the ventricular FT. We used regression analysis to obtain the best-fit model polynomial equation for the parameters. The concordance correlation coefficient (CCC) was used to assess intra- and inter-observer reproducibility.

Results: SDR and SDR' LV showed a progressive decrease with gestational age (GA); the SDR' RV and SDR' SEP did not show a significant decrease with advancing GA. The SDR LV (r = 0.29, p < 0.0001), SDR' RV (r = 0.21, p < 0.0001), SDR' LV (r = 0.20, p = 0.0001), and SDR' SEP (r = 0.25, p < 0.0001) showed a significant weak positive correlation with fetal heart rate. The inter-observer SDR' SEP measurements demonstrated poor reproducibility (CCC: 0.50), whereas intra-observer SRD LV measurements demonstrated moderate reproducibility (CCC: 0.78).

Conclusions: Reference values for SDR SEP, LV, and RV using spectral and tissue Doppler of fetal heart were established between 20 and 36+6 weeks of gestation.