Exercises in anatomy: tetralogy of Fallot

It is axiomatic that those performing surgery on the congenitally malformed heart require a thorough knowledge of the lesions they will be called upon to correct. The necessary anatomical knowledge is becoming increasingly difficult to obtain at first hand, since relatively few centres now hold archives of specimens obtained in an appropriately legal fashion from the patients unfortunately dying in previous years. One centre with such an archive is Ann and Robert H. Lurie Children's Hospital in Chicago, known previously as Chicago Memorial Children's Hospital. The archive was established by Farouk S. Idriss, and was subsequently enhanced and consolidated by his son, Rachid. It is now under the care of Carl L. Backer, the current chief of paediatric cardiothoracic surgery at Lurie Children's. With the support of Carl, the archive has been triaged and catalogued by Diane E. Spicer and Robert H. Anderson. It has now been used to create a series of video presentations, illustrating the salient features of surgical anatomy of selected entities, with the videoclips being edited and prepared for publication by Anne Sarwark. This video contains the fruits of the first of these exercises in anatomy, and is devoted to tetralogy of Fallot.We begin the exercise by making comparisons between the normal heart and the arrangement seen in typical tetralogy. We emphasize the need to recognize the 'building blocks' of the normal outflow tracts, and show how they come apart in tetralogy. We then show the variations to be found in the specific morphology of the borders of the hole between the ventricles, with the crest of the apical ventricular septum being overridden by the orifice of the aortic valve such that the latter structure has a biventricular connection. We emphasize that it is the squeeze between the deviated muscular outlet septum and septoparietal trabeculations that is the essential phenotypic feature of the lesion. We then proceed to demonstrate the further variation to be found in the length of the outlet septum, which in extreme cases can be fibrous and hypoplastic rather than muscular. We also show how the ventriculo-arterial connection can vary from being concordant to becoming double outlet from the right ventricle. We conclude by emphasizing that the anatomy of tetralogy can also be recognized when the subpulmonary outflow tract is atretic rather than stenotic.