Fetal color tissue Doppler imaging (cTDI): Analysis of time intervals during second and third trimester using different sized regions of interest

Purpose: To evaluate the correlation between cTDI-derived measurements of ventricular myocardium in healthy fetuses and the selected size of region of interest (ROI).

Material and methods: Preliminary multicenter prospective cross-sectional study in which 40 fetuses underwent cTDI. All fetuses were healthy, in sinus rhythm and had normal morphology. An AplioXG (Toshiba Medical Systems Corporation, Otawa, Tochigi, Japan) equipped with 1 – 5 MHz transducer was used in all centers. To achieve frame rates ≥100 frame/s the size of the scan area and the overlying color box in a longitudinal four chamber view were kept small. The cardiac cycles were digitally stored for later offline analysis. A large sample volume – including the whole free wall – and a 3 × 3 mm ROI was placed in the basal part of the RV and LV myocardium distal to the AV-valves. Early and late diastolic myocardial lengthening velocity (E', A'), systolic myocardial shortening velocity (S') and time intervals (ICT, ET, IRT) were obtained.

Results: Median gestational age at examination was 26+1 weeks (range: 20+5 – 34+4 weeks). Divided into two subgroups 20 patients were in the second and 20 in the third trimester. Median frame rate was 114 (range, 91 – 161) frames/s and median heart rate 143 (range, 122 – 165) bpm. Comparing small and large ROI time interval measurements revealed good correlations, whereas diastolic (E', A') and systolic peak velocities (S') exhibited wider ranges and highest values at the base.

Conclusion: Isovolumetric time intervals can be precisely analyzed independent of the ROI-size, whereas ET intervals reveal slighty different values. Myocardial tissue velocities are highest at the base and have wider normal ranges. Therefore, the small ROI is more suitable for analyzing peak velocities than a large ROI.