OC03.01: Abnormal cardiovascular 24‐segment sphericity index of the right and left ventricles in fetuses with growth restriction

Abstract

Introduction Fetuses with growth restriction have been reported to have an abnormal sphericity index (SI) of the right and left ventricles of the heart when dividing the end-diastolic basal-apical length by the basal transverse width for each chamber. This study was conducted to evaluate the SI for 24 transverse segments distributed from the base (segment 1) to the apex (segment 24) of the right and left ventricles to determine if an abnormal SI occurs at locations other than the basal segment. Methods Thirty fetuses with growth restriction were evaluated between 25 and 37 weeks of gestation. The SI was computed for the right (RV) and left (LV) ventricles by dividing the end-diastolic basal-apical length by each of the 24 end-diastolic transverse segmental widths from the base (segment 1) to the apex (segment 24). The Z-score and centile for the SI from each of the 24 segments from each ventricle were computed using the mean and standard deviation from published equations. The 24-segment method at which the SI was 90th centile was compared to the basal segment (1) using Chi-Square analysis to determine the number of fetuses with an abnormal SI. Findings In fetuses with growth restriction, an abnormal SI for any of the 24 transverse segments occurred in 73% (22/30) and was distributed as follows: 17% involved both ventricles, 23% involved only the right ventricle, and 33% involved only the left ventricle. Compared to the 24-segment model, using only the 1st basal segment from the right ventricle identified significantly fewer (58%, 7/12) fetuses with an abnormal SI (P<0.01). Similarly, using only the 12th segment in the mid-portion of the RV identified significantly fewer fetuses (50%, 6/12) with an abnormal SI (P <0.005). Combining measurements of both the 1st and 12th segments from the RV identified 83% of fetuses with an abnormal SI and was not significantly different from the 24-segment model. When compared to the 24-segment model, using only the 1st basal segment from the LV identified significantly fewer (63%, 10/16) fetuses with an abnormal SI (P<0.006). Similarly, using only the 12th segment in the mid-portion of the chamber identified (75%, 12/16), a significantly lower number of fetuses with an abnormal SI (P <0.03) when compared to the 24-segment model. Combining measurements of both the 1st and 12th segments identified 81% (13/16) of fetuses with an abnormal SI and was not significantly different from the 24-segment model. Conclusions The SI of 24-segments of the right and left ventricles provides a comprehensive method to examine the shape of the ventricular chambers and identifies more fetuses that are growth restricted with an abnormal SI than only using the basal segment.