The clinical anatomy of transposition

Extract

It is an easy matter, nowadays, to diagnose the clinical situation in which the blood returning to the atriums passes to the morphologically appropriate ventricle, but in which the ventricles then supply morphologically inappropriate arterial trunks. The consequence of this discordance in junctional morphology, of course, is that the circulations end-up in parallel, rather than in series, with the systemic venous return being channelled back to the body, and the pulmonary venous blood returning to the lungs (Fig. 1). In the absence of associated malformations, such as atrial or ventricular septal defects, or patency of the arterial duct, this morphological arrangement is incompatible with survival. Indeed, prior to the modern era, most infants born with this combination died in the first months of life.^1,2 Therapeutic innovations, notably the introduction of balloon atrial septostomy,³ have changed all that. Now, coupled with surgical advances, initially atrial redirection,^4,5 and then the arterial switch procedure,⁶ most neonates born with the malformation can anticipate a lengthy and good quality of life. Although there is now consensus concerning the clinical management of these segmental combinations, the best way of describing the morphological arrangement has been, and remains, fraught with difficulty.