Current echocardiographic assessment of fetal ventricular function uses relatively crude measures and this has led to inconsistencies in assessment of diastolic function. Long axis parameters may be more insightful.
Objective: To describe fetal long axis cardiac function and construct reference ranges.
Design: 159 normal fetuses were studied cross-sectionally using long axis M-mode to measure displacement of the atrioventricular ring and pulsed wave Doppler ultrasound to record myocardial tissue Doppler velocities at the base of the heart.
Results: There was a strong, almost linear gestational relationship for all but late left basal myocardial velocities. Systolic amplitude of the atrioventricular ring increased significantly. Wall thickness increased with gestation and heart rate reduced. Late diastolic mitral and tricuspid flow velocities showed no age-dependence. Right ventricular filling (p<0.0001) and myocardial lengthening (p<0.0001) and shortening velocities (p<0.0001) were higher than left. Aortic velocities were higher than pulmonary (p<0.0001). Right ventricular long axis amplitude was greater than left (p<0.0001). There were no significant differences in right (RV) and left (LV) ventricular and septal thicknesses (RV 2.5 mm [1.2-4.1]; LV (2.4 mm [1.0-4.0] and septum 2.6 mm [1.0-4.3]). Left and right myocardial tissue Doppler velocities showed similar maturation in systole (LV 0.14 vs. RV 0.10 cm/s/week) and early diastole (LV 0.16 vs. RV 0.14 cm/s/week).
Conclusions: This study demonstrates maturational changes occur in both fetal systolic and diastolic ventricular function and moreover the maturational rate of myocardial tissue velocities is similar in both ventricles, despite differential loading conditions.