Introduction
Deficient ventricular septation is the commonest abnormality found when
the heart is congenitally malformed. It can be found in isolation, or as
an integral part of multiple lesions. When encountered as the major
problem, the arrangement is appropriately described in terms of
ventricular septal defects. When deficient septation is part of lesions
such as double outlet right ventricle, or common arterial trunk, the
channel between the ventricles is more accurately considered as an
interventricular communication.1 Such distinctions,
however, are largely of semantic interest. The understanding of the
differences in the terms, nonetheless, is key to appropriate surgical
management. This is also the case when the defects are multiple. It is
now agreed that, when considered as an overall group, and taking account
of the fact that the communications can also be part of more complex
lesions, the defects themselves, when assessed in isolation, exhibit one
of three phenotypic patterns. There are the muscular, perimembranous,
and juxta-arterial variants.2 When approached on this
basis, it should be no surprise that the perimembranous, or
juxta-arterial, variants can co-exist with additional channels within
the muscular ventricular septum. Several discrete channels can also be
found within the confines of the muscular septum itself. On occasion,
furthermore, the multi-fenestrated septum is justifiably compared to
Swiss cheese. Yet another subtly different arrangement is found when a
solitary channel within the apical part of the muscular septum is
crossed, on the right ventricular side, by multiple
trabeculations.3 This gives the spurious impression of
multiple defects.4 The recent analysis of the trawl of
surgical results made by the Society of Thoracic Surgeons revealed that
both mortality and morbidity were increased in the setting of multiple
as opposed to solitary ventricular septal defects.5-9The surgical approach in presence of multiple defects, however, is
likely to be different depending on the combinations of individual
defects. It is unlikely that the same operative intervention will be
optimal for each of the different patterns. To the best of our
knowledge, the significance of these different associations between
multiple defects has yet to be explored in the context of therapeutic
management. In this, the introduction to a review of such management, we
have described the developmental background to the existence of multiple
defects. We demonstrate the phenotypic combinations, and discuss their
anatomical features. In our subsequent review, we will discuss the
significance of the anatomical variations to diagnosis and options for
treatment.