The atrioventricular junctions in Ebstein malformation
- aPaediatrics, National Heart and Lung Institute, Royal Brompton Campus, Imperial College of Science, Technology and Medicine, Dovehouse Street, London SW3 6LY, UK, bFetal and Perinatal Cardiology, Guy's Hospital, London SE1, UK, cDepartment of Anatomy, Institute of Child Health at Alder Hey, Liverpool, UK
- Dr Ho email: yen.ho{at}ic.ac.uk
- Accepted 23 November 1999
Abstract
OBJECTIVE To review the anatomical structure of the right atrioventricular junction, including the specialised atrioventricular conduction system, in hearts with Ebstein's malformation, to identify potential substrates for the abnormalities in conduction.
METHODS Five heart specimens representing the morphological spectrum of Ebstein malformation were examined grossly and histologically.
RESULTS On the endocardial surface, the atrioventricular junction was marked by a faint line in two hearts, and by a small ridge in the other three. Analysis of the right parietal junction in four hearts revealed only two accessory muscular atrioventricular connections. A plane of fibrofatty tissue separated atrial from ventricular myocardium in the right parietal junction in all hearts. The compact atrioventricular node was closer to the coronary sinus than usual. Accessory nodoventricular connections were present in four hearts, while accessory fasciculo-ventricular connections were found in one. The right bundle branch was hypoplastic or absent in four hearts.
CONCLUSIONS In this small series, the parietal atrioventricular junction was better developed than previously thought. Structural abnormalities of the atrioventricular conduction system, however, were present. These may account for some of the conduction abnormalities frequently observed with the Ebstein malformation.
