Discussion
As we have shown, multiple, or seemingly multiple, ventricular septal
defects can be found in three discrete patterns. In the first
arrangement, separate and discrete defects co-exist within different
parts of the ventricular septum. Most usually this is because of a
combination of perimembranous and muscular defects. This variant is of
particular surgical significance when the muscular defect opens to the
inlet of the right ventricle. This is because the atrioventricular
conduction axis is particularly vulnerable in this setting (Figure 7).
The second arrangement is found when the muscular ventricular septum has
failed properly to coalesce during cardiac development. This then
produces two variants according to the extent of coalescence. When less
severe, multiple discrete holes can be observed within the muscular
septum, usually at the borders between the right ventricular inlet and
outlet and the apical part of the septum. It is the more severe end of
the spectrum of failure of coalescence that manifests as the so-called
Swiss-cheese septum. This variant poses perhaps the greatest challenge
for surgical correction. The final arrangement is not truly an example
of multiple defects. It is found when a large, but solitary, defect in
the apical part of the muscular septum is crossed in the right ventricle
by trabeculations, giving the spurious impression of multiple
defects.4 The surgical approach to each of these
variants will itself vary, although several options have been proposed
for each specific sub-set. It is those options that we will discuss in
the our surgical review.