Transposition – Introduction

Extract

In the past, most arguments concerning transposition devolved on how best to define it. When Mathew Baillie described the first case, at the end of the eighteenth century, he had no problems. He simply called it a singular malformation!¹ Subsequent to Baillie's description, arguments raged amongst morphologists and pathologists as to whether the entity was best described on the basis of how the aorta was related to the pulmonary trunk, or according to the origin of the arterial trunks from inappropriate ventricles. There is little doubt now that all clinicians diagnose transposition on the basis of discordant origin of the arterial trunks from the ventricular mass, although there is still debate as to whether this discordant origin is best described in terms of connections² or alignments.³ There remain some, nonetheless, who still describe entities such as “double outlet with transposition”, using this phrase to describe the arrangement in which both arterial trunks arise from the right ventricle, but with the aorta positioned anteriorly. For those adopting the concepts of connections or alignments, this combination is clearly impossible.⁴ Yet for those who choose to define “transposition” on the basis of the anterior location of the aorta,⁵ this would remain an entirely logical description. These problems of nomenclature, and many more aspects of the morphology of discordant origin of the arterial trunks from the ventricular mass, are discussed at length in the first review of this part of the supplement,⁶ co-authored by myself, who believes firmly in the concept of connections, and Paul Weinberg, who is equally convinced that the cardiac segments are best described in terms of alignments rather than connections. Our joint review hopefully shows that differences in nomenclature nowadays are relatively minor, and even where they exist, they do not stand in the way of reaching consensus on how best to describe the segmental combination in which the atrial chambers are joined to morphologically appropriate ventricle, but the ventricles support morphologically inappropriate arterial trunks. It is this particular morphological arrangement that, for the purposes of this section of our supplement, is described as “transposition”.