Objective: To investigate the relationship between parameters of diastolic function, loading conditions and remodeling of the left ventricle in the appropriate-for-gestational age and small-for-gestational age fetus.
Methods: Two-dimensional echocardiographic left ventricular images were digitized in 24 appropriate-for-gestational age and 14 small-for-gestational age fetuses. The maximal short axis and long axis were measured. The left ventricular contour was divided into 12 segments. The changes in whole left ventricular cavity area were calculated for ventricular global area change assessment. The coefficient of variation for segmental fractional area change was calculated for the evaluation of left ventricular regional wall motion non-uniformity.
Results: Mean left ventricular long axis/short axis ratio in the small-for-gestational age fetus (1.11 +/- 0.08) was smaller (P < 0.01) than in the appropriate-for-gestational age fetus (1.75 +/- 0.26). Mean fractional area change in the small-for-gestational age fetus was larger (P < 0.01) than in the appropriate-for-gestational age fetus (37.8 +/- 17.6% vs. 21.1 +/- 9.9%). Mean left ventricular global area change in the small-for-gestational age fetus was smaller (P < 0.05) than in the appropriate-for-gestational age fetus (53.2 +/- 7.4% vs. 61.5 +/- 10.3%). Mean ventricular isovolumic relaxation time in the appropriate-for-gestational age fetus was shorter (P = 0.03) than in the small-for-gestational age fetus (37 +/- 6 ms vs. 57 +/- 9 ms). Mean transmitral E-wave/A-wave ratio in the small-for-gestational age fetus was smaller (P < 0.01) than in the appropriate-for-gestational age fetus (0.69 +/- 0.08 vs. 0.80 +/- 0.08). A negative correlation (P < 0.05) was demonstrated between: (i) fractional area change and global area change in both small-for-gestational age (r = -0.62) and appropriate-for-gestational age fetuses (r = -0.58); (ii) umbilical artery systolic/diastolic ratio and transmitral E-wave/A-wave ratio in both appropriate-for-gestational age (r =-0.58) and small-for-gestational age (r = -0.60) fetuses. A positive correlation existed between fractional area change and isovolumic relaxation time in the small-for-gestational age fetus (r = +0.72; P < 0.01).
Conclusions: The changes in ventricular shape, wall motion, spatial non-uniformity and diastolic function in the small-for-gestational age fetus could be considered as adaptive changes, known as ventricular remodeling. It is proposed that the leading cause of ventricular remodeling in the small-for-gestational age fetus is chronic pressure overload due to increased placental vascular resistance.