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

Our objective was to explore whether minor anatomical abnormalities of the septal insertion of tricuspid and mitral valves could be a feature of trisomy 21 in fetuses with an otherwise normal heart. Postmortem examinations were performed in 41 fetuses affected by Down's syndrome and in 52 controls. Adjoining the standard postmortem procedure, an apex-to-base section of the crux of the heart was made on a plane corresponding to the sonographic four-chamber view. This allowed gross and histological examination of the hinge points of tricuspid and mitral leaflets, showing the usual apical displacement of the tricuspid valve in all controls. Of 41 fetuses affected by Down's syndrome, 18 had a structural heart defect. Of the 23 Down syndrome fetuses without a patent heart defect, 16 (i.e., 69% of those considered as having 'normal hearts') had nevertheless a linear insertion of atrioventricular valves at autopsy. Prospective clinical studies are required to evaluate if these postmortem findings can be transposed to the clinical setting of 2nd-trimester sonographic screening.