Quantitation of Fetal Heart Function With Tissue Doppler Velocity Imaging-Reference Values for Color Tissue Doppler Velocities and Comparison With Pulsed Wave Tissue Doppler Velocities

Quantitative assessment of fetal heart function has been difficult. Increasingly, tissue Doppler imaging (TDI) is used to measure fetal cardiac function noninvasively. There are two principal techniques, spectral pulsed wave (PW) TDI and color TDI (CTDI). Published reference values for fetal myocardial velocities are based on spectral PW TDI only. However, previous phantom, adult, and animal studies have shown that PW TDI velocities are systematically higher than CTDI velocities. There are no fetal studies so far. We hypothesized that myocardial velocities derived by PW TDI and CTDI are significantly different in the fetus. This prospective observational study included 91 fetuses (gestational age 28.6±6.6 weeks; range 19-40 weeks) seen for routine prenatal ultrasound. From apical 4-chamber views, tricuspid ring (right ventricle), lateral and septal mitral ring were sampled by PW TDI and CTDI. Bland-Altman analysis was used for comparisons. PW and CTDI S′ velocities correlated strongly in all three cardiac segments (r=0.6 to 0.9; P<0.01). There was a systematic bias toward higher velocities with PW TDI versus CTDI (bias 0.96cm/s; 95% CI 1.08-0.85cm/s). However, the strength of the correlation and bias varied depending on the region of the fetal heart sampled. PW TDI and CTDI velocity measurements are feasible in the fetus and correlate well. However, PW TDI velocities are higher than CTDI velocities with significant regional variation. This precludes a mathematical conversion of PW to CTDI in vivo. As PW TDI and color TDI vary, different reference values for fetal CTDI velocities were generated.