Tissue Doppler imaging of the fetal heart

Objectives The objectives of this study were: (i) to assess the feasibility of a tissue Doppler imaging (TDI) evaluation in the fetus, (ii) to identif y color-TDI patterns consistent with the various phases of the cardiac cycl e; and (iii) to assess myocardial velocities and the myocardial velocity gr adient. Methods Eighty-nine normal fetuses between the 17th and the 37th week of ge station were studied. Color-TDI was superimposed on an apical four-chamber view of the fetal heart and three cardiac cycles captured in cine-loop form at. By reviewing the cine-loop strip, color patterns consistent with the va rious phases of the cardiac cycle were identified. The procedure was then r epeated with a transverse four-chamber view. On each frame corresponding to mid-systole, early and late diastole, myocardial velocities were calculate d at the subepicardial and subendocardial layer and regressed against gesta tional age. Statistics included correlation and regression analysis, calcul ation of the 95% confidence intervals and of the Cronbach's alpha reliabili ty coefficient for repeated observations. Results TDI examination is acceptably reproducible in the fetus. We were ab le to identify color-TDI patterns depicting the systolic contraction wave, ventricular relaxation and atrial contraction. Statistical evaluation demon strated that: all variables (systolic right and left subendocardial and sub epicardial velocities, early diastolic right and left subendocardial and su bepicardial velocities, end diastolic right and left subendocardial velocit ies, right subepicardial velocities) except end-diastolic right and left su bepicardial velocities, showed a positive correlation with advancing gestat ional age; subendocardial velocities were higher than subepicardial ones th roughout the cardiac cycle in both ventricles; systolic myocardial velociti es were higher in the left ventricle whereas early diastolic velocities wer e higher in the right ventricle; and the ratio between early and late diast olic subendocardial velocities (E-M/A(M)) was constantly <1 and did not cha nge with advancing gestational age. Conclusions TDI evaluation of the fetal heart is feasible and reproducible. Color-TDI is able to identify the various phases of the cardiac cycle. Qua ntitative evaluation of myocardial velocities has shown also in the fetus t he existence of the myocardial velocity gradient found in postnatal life.