Evaluation of normal fetal atrio-ventricular septum dimensions during pregnancy

Measuring the Area of the Interventricular Septum in the 4-Chamber View: A New Technique to Evaluate the Fetus at Risk for Septal Hypertrophy

OBJECTIVES

One of the problems for the clinician who desires to measure the interventricular septum (IVS) in a high-risk fetus is to know where to make the measurement. The purpose of this study was to use speckle-tracking analysis to measure the IVS area, 24-segment widths, and length at end-diastole (ED) and end-systole (ES) in normal fetuses.

METHODS

From the 4-chamber view, speckle-tracking analysis was performed at ED and ES on the IVS in 200 normal fetuses. The following were computed and regressed against gestational age (GA) and fetal biometric (FB) measurements: area, length, and the 24-segment transverse widths from the apex to the crux. The 24-segment width/length ratio was also measured. The speckle-tracking measurements of the ED area and length were compared using a point-to-point measurement tool available on all ultrasound machines.

RESULTS

The ED and ES areas, lengths, and 24-segment widths increased with GA and FB. The ED and ES areas were virtually identical. The 24-segment width/length ratio decreased from the apex to the crux of the septum. There was no significant difference in the measurement of the ED area and the length between speckle-tracking and the point-to-point measurements.

CONCLUSIONS

Measurement of the area and length of the IVS are simple to obtain and provide a new diagnostic tool to evaluate the fetus at risk for IVS hypertrophy which may be observed in fetuses of mothers with pregestational and gestational diabetes.

Z-Score Reference Ranges for the Offset of the Tricuspid Septal Leaflet in Normal Fetuses

OBJECTIVES

To determine Z-score equations and reference ranges for mitral valve-tricuspid valve distance (MTD) and the MTD index in the fetal heart.

METHODS

A prospective cross-sectional study was performed in 899 normal singleton fetuses from 14 to 40 weeks' gestation. The MTD and interventricular septum length (IVSL) were measured offline after electronic cardiac spatiotemporal image correlation volume acquisition. The MTD index was determined as the ratio of MTD to IVSL. Z-score reference ranges of these measurements were determined against gestational age (GA) and estimated fetal weight (EFW), using regression analysis of the mean and standard deviation (SD).

RESULTS

Strong positive correlations were found between the MTD and the independent variables. A simple linear regression model was the best description of the mean and SD of MTD based on GA, while a cubic regression best fitted the mean MTD against EFW. In contrast, the MTD index decreased progressively with the independent variables. Fractional polynomials best fitted the MTD index in terms of GA and EFW.

CONCLUSION

Normal reference values and Z-scores of fetal MTD and MTD index were provided against GA and EFW, which may be useful tools for quantitative assessment of some cardiac and extracardiac diseases.

Differential and linear insertion of atrioventricular valves: a useful tool?

OBJECTIVE

The differential insertion of the atrioventricular valves is the ultrasonographic representation of the more apical attachment of the tricuspid valve to the septum with respect to the mitral valve. A linear insertion is present when both valves form a linear continuum and has been suggested as a marker for atrioventricular septal defects (AVSDs). The objective of this study was to evaluate the anatomical substratum of differential and linear insertions of the atrioventricular valves in normal fetal hearts and fetal hearts with an AVSD.

METHODS

The extent and position of the fibrous skeleton and attachment of the atrioventricular valves to the septum were studied in histological sections of 17 normal hearts and four hearts with an AVSD from 10 + 0 weeks' gestation to 3 days postpartum with various immunohistochemical tissue markers. In addition, spatiotemporal image correlation (STIC) volumes of 10 normal hearts and STIC volumes of eight hearts with an AVSD at 13 + 6 to 35 + 5 weeks' gestation were examined.

RESULTS

The differential insertion of the atrioventricular valves was visible in normal hearts in the four-chamber plane immediately beneath the aorta, but nearer the diaphragm a linear insertion was found. In hearts with an AVSD, a linear appearance was observed in the four-chamber plane immediately beneath the aorta. Towards the diaphragm, however, first a differential insertion and, more caudally, a linear insertion was found.

CONCLUSIONS

Both differential and linear insertions can be found in normal fetal hearts and fetal hearts with AVSD, depending on the plane in which the four-chamber view is visualized. Therefore, measurement of the differential insertion is likely to be useful only in experienced hands.

Differential insertion of the atrioventricular valves: measurement protocol to detect various congenital heart defects

OBJECTIVES

The objectives of this study were to develop reference values for the distance between the atrioventricular valves, called differential insertion of the atrioventricular valves (DIAVV), in normal fetuses using four-dimensional ultrasound with spatio-temporal image correlation and to explore if DIAVV measurement can differentiate between normal hearts and hearts with cardiac defects.

METHODS

The DIAVV was analysed longitudinally following a measurement protocol in 74 fetuses between 15 and 36 weeks gestational age. The DIAVV was measured in an apical four-chamber view of the heart in end-diastole. Furthermore, the DIAVV was measured in 70 fetuses with cardiac defects.

RESULTS

In total, 337 normal and 70 abnormal spatio-temporal image correlation volumes were examined. Longitudinal regression analysis revealed a positive relationship of the DIAVV with gestational age and fetal biometry (p < 0.0001). The DIAVV of fetuses with double outlet right ventricle, truncus arteriosus, atrioventricular septal defects, Ebstein and tetralogy of Fallot all differed from normal fetuses (p < 0.05).

CONCLUSION

Measurement of the DIAVV is a promising tool; however, a well-defined measurement protocol should be followed to accomplish the correct plane and exact moment in the cardiac cycle. This study presents new nomograms following this measurement protocol and reports an abnormal DIAVV in a wide spectrum of congenital heart disease.