Linear insertion of atrioventricular valves without septal defect: a new anatomical landmark for Down's syndrome?

Evaluation of septal insertion of atrioventricular valves in fetuses by postmortem 4.7 Tesla cardiac MRI: A feasibility study

PURPOSE

The purpose of this study was to compare non-invasive high-spatial-resolution postmortem cardiac magnetic resonance imaging (MRI) and autopsy findings for evaluating the septal insertion of atrioventricular valves in fetuses.

MATERIALS AND METHODS

Five fetal heart specimens including two normal hearts, one heart with complete atrioventricular septal defect (AVSD) and two hearts with linear insertion of atrioventricular valves (LIAVV; gestational age 17 to 34 weeks) were studied with cardiac MRI using a 4.7 T MRI scanner without sample preparation. Three (3D) and two-dimensional (2D) turbo-RARE (rapid imaging with refocused echoes) sequences in four-chamber and left-ventricular long-axis planes were obtained with a minimal isotropic/in-plane resolution of 156μm. Nonparametric tests were performed to compare the distance between insertions of medial leaflets of the atrioventricular valves and the inlet/outlet distance ratio between MRI and autopsy findings in normal, complete AVSD and with linear insertion of atrioventricular valves (LIAVV) fetal hearts.

RESULTS

Despite apparent differences between LIAVV/normal hearts, no significant differences were found between differential insertion of medial leaflets and inlet/outlet distance ratios with both techniques. Very good to excellent reliability between both techniques was found for differential insertion (ICC: 87.2%; 95% CI: -21.7%, 99.1%) (P=0.963) and inlet/outlet distance ratio (ICC 98.3%; 95%CI: 85.2%, 99.8%) (P=0.537) measurements.

CONCLUSION

Postmortem cardiac MRI could replace autopsy for assessing normal or abnormal septal insertion of atrioventricular valves in fetuses without requiring specific preparation of the heart.

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.

Two Cases of Prenatally Diagnosed Membranous and Muscular Ventricular Septal Aneurysms

A ventricular septal aneurysm is a rare heart defect located in the muscular or membranous part of the septum. Muscular ventricular septal aneurysms are usually isolated, with a favorable prognosis. Membranous ventricular septal aneurysms are often associated with other heart anomalies, could result in serious complications, and may require surgical treatment. We describe 2 cases of prenatally diagnosed ventricular septal aneurysms: an isolated membranous ventricular septal aneurysm with a good outcome, which was initially misdiagnosed as an atrioventricular septal defect; and a muscular ventricular septal aneurysm associated with a hypoplastic aortic arch and severe hydrocephaly, which resulted in termination of the pregnancy. To our knowledge, the combination of a muscular ventricular septal aneurysm with an extracardiac anomaly has not been reported previously.

Angiogenic Gene Expression in Down Syndrome Fetal Hearts

INTRODUCTION

Forty percent of Down syndrome (DS) fetuses have congenital heart defects (CHD). An abnormal angiogenic environment has been described in euploid fetuses with CHD. However, the underlying pathophysiologic pathway that contributes to CHD in DS remains unknown. The objective was to compare the expression of angiogenic factors and chronic hypoxia genes in heart tissue from DS and euploid fetuses with and without CHD.

METHODS

The gene expression profile was determined by real-time PCR quantification in heart tissue from 33 fetuses with DS, 23 euploid fetuses with CHD and 23 control fetuses.

RESULTS

Angiogenic factors mRNA expression was significantly increased in the DS group compared to the controls (soluble fms-like tyrosine kinase-1, 81%, p = 0.007; vascular endothelial growth factor A, 57%, p = 0.006, and placental growth factor, 32%, p = 0.0227). Significant increases in the transcript level of hypoxia-inducible factor-2α and heme oxygenase 1 were also observed in the DS group compared to the controls. The expression of angiogenic factors was similar in DS fetuses and CHD euploid fetuses with CHD.

CONCLUSION

Abnormal angiogenesis was detected in the hearts of DS fetuses with and without CHD. Our results suggest that DS determines an intrinsically angiogenic impairment that may be present in the fetal heart.

How Normal is a 'Normal' Heart in Fetuses and Infants with Down Syndrome?

BACKGROUND

Congenital heart disease is present in 44-56% of fetuses with Down syndrome (DS). There are, however, signs that hearts in DS without apparent structural heart defects also differ from those in the normal population. We aimed to compare the atrioventricular (AV) septum and valves in 3 groups: DS without AV septal defect (DS no-AVSD), DS with AVSD (DS AVSD) and control hearts.

METHODS

The ventricular septum, membranous septum and AV valves were examined and measured in histological sections of 15 DS no-AVSD, 8 DS AVSD and 34 control hearts. In addition, the ventricular septum length was measured on ultrasound images of fetal (6 DS AVSD, 9 controls) and infant (10 DS no-AVSD, 10 DS AVSD, 10 controls) hearts.

RESULTS

The membranous septum was 3 times larger in DS no-AVSD fetuses compared to control fetuses, and valve dysplasia was frequently (64%) observed. The ventricular septum was shorter in patients with DS both with and without AVSD, as compared to the control group.

CONCLUSION

DS no-AVSD hearts are not normal as they have a larger membranous septum, shorter ventricular septum and dysplasia of the AV valves as compared to control hearts.

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.

Mitral valve-tricuspid valve distance as a sonographic marker of trisomy 21

OBJECTIVE

Pathologic studies suggest that a decreased mitral valve-tricuspid valve distance (MTD) is found in trisomy 21 fetuses without cardiac defects. We assessed the feasibility of using the MTD as a second-trimester sonographic marker for trisomy 21.

METHODS

We performed a retrospective case-control study of all cases of trisomy 21 at our institution from 1998 to 2008. Cases without a prenatally identified cardiac defect and with adequate images from 15 to 26 weeks' gestation were assessed. The distance between the medial insertions of the mitral and tricuspid valves (i.e. the MTD) onto the ventricular septum was obtained. We also obtained the MTD from normal controls during the study period. Multiple linear regression analysis was used to assess the effects of gestational age and trisomy 21 on MTD. Gestational age-specific percentiles and multiples of the median were calculated, and curves were fitted using linear regression analysis.

RESULTS

We identified 57 trisomy 21 fetuses with a measurable MTD and compared these with 634 control fetuses. Multiple linear regression analysis revealed a positive correlation between MTD and gestational age and a negative correlation between trisomy 21 and MTD. Using a cut-off of the 5(th) percentile, the MTD detected 70% of trisomy 21 cases with a 3.8% false-positive rate in the controls.

CONCLUSIONS

The MTD increases with gestational age and is lower in fetuses with trisomy 21. Twenty (35%) of the 57 cases had no sonographic marker of trisomy 21 except an MTD below the 5(th) percentile for gestational age. The MTD was a useful independent marker for trisomy 21 in the second trimester.

[Linear insertion of atrioventricular valves (Livav): echocardiographic diagnosis, reliability and prevalence in the general population]

OBJECTIVES

Assess the reliability of prenatal diagnosis of linear insertion of atrioventricular valves (Livav) by echocardiography as well as estimate Livav's prevalence in a population without Down syndrome.

PATIENTS

One hundred and twenty-three fetuses of whom 113 were explored before and after birth and 631 consecutive out-patients explored in cardiopediatric unit.

METHODS

Determination of the likehood ratio (LHR+ and LHR-) of Livav prenatal diagnosis. Evaluation of the consistency between pre- and postnatal diagnoses as well as between two observers after birth (Kappa index). Prevalence study according to the presence of Down syndrome, cardiac malformation or others abnormalities.

RESULTS

LHR+ value was 6.17 and LHR- value was 0.30 for echographic Livav prenatal diagnosis. Consistency was low between pre- and postnatal diagnoses (Kappa = 0.57) and higher between two observers after birth (Kappa = 0.79). Livav prevalence was 2 to 5% in a population without Down syndrome but 15% when associated with a cardiac malformation. Seventy-eight percent Down syndromes had either Livav or AVSD.

CONCLUSION

Livav echographic prenatal diagnosis is difficult, for it generates many false positives. Livav is not specific of Down syndrome and can be found relatively frequently in other subjects.

On being at higher risk: A qualitative study of prenatal screening for chromosomal anomalies

This paper explores the meaning of higher risk status to women undergoing prenatal maternal screening for chromosomal anomalies. Quotations from lightly structured interviews and transcripts of pre-screening consultations in suburban London are used to illustrate pregnant women's diverse responses to the offer of screening, and to entering, living with and exiting from higher risk status. Some women reject screening in order to avoid the psychosocial and medical risks associated with higher risk status, or because they rule out pregnancy termination. They may question the risk selection implicitly built into the provision of preventative systems for some health problems but not others. Women who screen at higher risk may challenge this designation by questioning the system-specific probability used to separate them from the lower risk population. However, some experience distress even when they appreciate the precautionary basis on which their higher risk designation is based. They may find disengagement from higher risk status difficult after a diagnostic test has ruled out chromosomal anomalies. The findings highlight the complexity of communicating risk information to pregnant women and other screened populations, and emphasise the need to support those living with higher risk status and the benefits of keeping the time lived with this status as short as possible.

Nouvelle coupe du cœur en fœtopathologie

Our findings on hearts of trisomic 21 fetuses of a new minor cardiac anomaly, belonging to the atrioventricular septal defect (AVSD) spectrum and the improved performances of the fetal ultrasound screening lend us to propose a new section, complementary to the standard cardiopathological examination. It would enable us to test the anatomic level of insertion of the atrioventricular valves of the crux of the heart. It consists of a section of the fetal hearts, fixed in formaldehyde, in a plane correlated to the plane of the fetal ultrasonographic four chamber view. Three hallmarks have been chosen because of their relevance and of their reproductibility in ultra sonography as well as in fetopathology: the apex and the inferior pulmonary veins. This additional section was realized on fetal hearts, regarded as "normal" with the standard pathologic examination, because of a lack of defect. It allowed us to detect a minor cardiac abnormality of the AVSD spectrum, frequent in the trisomic 21 fetuses, which we called: linear insertion of the atrio ventricular valves( LIAVV) without defect. Initially described on a series of Trisomic 21 fetal hearts, the LIAVV without defect has also been found in other fetuses with another pathology often associated with an anomaly of the AVSD spectrum. The possible detection of this abnormality in fetal cardiac ultrasound scanning justifies the use of this new anatomical technique. It also has to be included it in the full standard pathologic examination of the fetal hearts of all the abnormal fetuses.

Prenatal diagnosis of membranous ventricular septal aneurysms and their association with absence of atrioventricular valve 'offsetting'

Congenital aneurysm of the membranous portion of the ventricular septum in association with absence of atrioventricular valve 'offsetting' was diagnosed in two fetuses at 29 and 34 weeks. In the first case the fetus had a normal karyotype and no other structural heart defects, whereas in the second case there was a partial deletion of the long arm of chromosome 5 and an absent pulmonary valve syndrome. The association of absence of 'offsetting' with aneurysms of the membranous ventricular septum may represent spontaneous closure of ventricular septal defects initially extended to the inlet.