Understanding the nature of congenital division of the atrial chambers

Although the atriums must bow to the ventricles in terms of the power and complexity of the contractions of their muscular walls, morphologically they are far more complex than the mere forechambers implied by their classical name (defined in the Shorter Oxford Dictionary as "a portico in front of the principal doors of churches, etc".' The atriums are particularly important to those practitioners dealing with cardiology in the young, since recognition of their arrangement is the first step in the process ofdiagnosis now known generally as sequential segmental analysis.23 In addition to recognising the disposition of the atriums relative to each other, however, the paediatric cardiologist must also recognise atrial malformations, no matter how rare or arcane they may be. It is a truism that recognition of such lesions is greatly enhanced when their morphology is understood. This sets the scene for the discussion of hearts characterised by some degree of congenital partitioning within the morphologically left atrium. The reports collected in this issue of the British Heart Journal describe the use of colour flow mapping in diagnosis of division of the left atrium in association with congenitally corrected transposition;4 diagnosis of a more classic case of divided left atrium by transoesophageal echocardiography;5 and, perhaps most interestingly, a description of two cases with a prominent shelf guarding the entrance of the left pulmonary vein to the left atrium.6 Although all the authors point to the rarity of such malformations, the April issue of Pediatric Cardiology too carries a report of a rare variant of divided left atrium,7 as well as an account ofthe experience ofColumbia University, New York, over a 28 year period, which encompassed 12 cases.8 The importance of these lesions to all cardiologists is emphasised by the fact that both the patients from Boston6 were adults referred for evaluation of a left atrial mass detected echocardiographically, while the patient studied at the Royal London Hospital was also an adult presenting with mitral stenosis in the third decade of life.5 No longer, therefore, can adult cardiologists claim that such cases do not influence their practice. They may be rare but, as shown in these reports, they are readily recognised by cross sectional echocardiography and, providing their anatomy is understood they are easy to categorise and describe.