Figure Legends
Figure 1. The images show the arrangement of the developing heart at the
stage of the beginning of formation of the muscular ventricular septum.
The left hand panel shows a section from a murine embryo sacrificed on
embryonic day 10, while the right hand panel shows a reconstruction of
the cavities of the developing human heart at around 5 weeks of
development, which is graded as Carnegie stage 13. The star shows the
site of formation of the apical muscular septum, separating the
ballooning apical ventricular components.
Figure 2. The images show the stages of remodelling of the primary
interventricular communication to form the secondary and tertiary
communications in the developing murine heart. Panel A shows the stage
subsequent to expansion of the atrioventricular canal. Panel B, at a
later stage, shows how the proximal outflow cushions have fused (dotted
line) to form a shelf in the roof of the right ventricle. Panel C, from
the same heart, shows the persisting tertiary interventricular
communication between the aortic root and the cavity of the right
ventricle.
Figure 3. The images show the different types of defects produced in
developing mice in which the Furin enzyme has been perturbed. Panel A
shows the non-compacted apical muscular septum in a heart which also
shows an ostium primum defect. Panel B shows a perimembranous defect,
while panel C shows an outlet defect that is juxta-arterial because of
failure of formation of the subpulmonary infundibulum.
Figure 4. The images show the features of the different types of
ventricular septal defects as determined on the basis of their borders.
Panel A shows the features of a muscular inlet defect, with panel B
showing a perimembranous defect, both in cuts replicating the
echocardiographic four-chamber plane. Panel C shows a juxta-arterial
defect in a cut simulating the parasternal long axis plane.
Figure 5. The images show multiple muscular defects found at the border
between the inlet of the right ventricle and its apical component when
there has been a degree of inappropriate coalescence of the septum
during development. Panel A shows the view from the right ventricular
aspect. As can be seen when assessing the situation from the left
ventricular apex (Figure 5B). the most apical part of the septum is
intact.
Figure 6. The images show the situation produced when there has been
severe lack of coalescence of the muscular ventricular septum during
cardiac development. Panel A shows the right ventricular aspect, with
Panel B showing the view from the left side. Although the entire apical
part of the septum has failed to coalesce, it is difficult to identify
individual defects. Note also the excessive apical trabeculation in the
left ventricle.
Figure 7. The images show multiple defects produced by the combination
of perimembranous and muscular inlet defects. The red dashed line shows
the location of the atrioventricular conduction axis, which runs through
the myocardial bar separating the defects. The defects are shown from
the right (panel A) and left (panel B) ventricular aspects.
Figure 8. The images show how a solitary defect when viewed from the
left ventricle (panel A) can seem to represent multiple defects when
viewed from the right ventricle (panel B).