This Article Full Text Full Text (PDF) All Versions of this Article: 96/7/776    most recent 01.RES.0000162000.03997.65v1 Alert me when this article is cited Alert me if a correction is posted Citation Map Services Email this article to a friend Similar articles in this journal Similar articles in PubMed Alert me to new issues of the journal Download to citation manager Request Permissions Citing Articles Citing Articles via HighWire Citing Articles via Google Scholar Google Scholar Articles by Jongbloed, M.R.M. Articles by Gittenberger-de Groot, A.C. Search for Related Content PubMed PubMed Citation Articles by Jongbloed, M.R.M. Articles by Gittenberger-de Groot, A.C. Related Collections Arrythmias-basic studies Cardiac development

(Circulation Research. 2005;96:776.)
© 2005 American Heart Association, Inc.

Integrative Physiology

Development of the Right Ventricular Inflow Tract and Moderator Band

A Possible Morphological and Functional Explanation for Mahaim Tachycardia

M.R.M. Jongbloed, M.C.E.F. Wijffels, M.J. Schalij, N.A. Blom, R.E. Poelmann, A. van der Laarse, M.M.T. Mentink, Z. Wang, G.I. Fishman, A.C. Gittenberger-de Groot

From the Departments of Anatomy and Embryology (M.R.M.J., R.E.P., M.M.T.M., A.C.G.-d.G.), Cardiology (M.R.M.J., M.C.E.F.W., M.J.S., A.v.d.L.), and Paediatric Cardiology (N.A.B.), Leiden University Medical Center, Leiden, The Netherlands; and the Leon H. Charney Division of Cardiology (Z.W., G.I.F.), New York University School of Medicine, New York, NY.

Correspondence to Prof Dr A.C. Gittenberger-de Groot, Dept of Anatomy and Embryology, Wassenaarseweg 62, PO Box 9602, 2300 RC Leiden, The Netherlands. E-mail acgitten{at}lumc.nl

Atriofascicular accessory bundles with AV-node like conduction properties can sustain atrioventricular (AV) re-entrant tachycardia (Mahaim tachycardia). During early embryogenesis, the AV canal is situated above the primitive left ventricle (LV), and a right AV connection has not been achieved yet. We studied the formation of the right ventricular (RV) inflow tract in relation to the developing cardiac conduction system and hypothesized a morphological explanation for functional atriofascicular bypass tracts. Analysis of lacZ-expression during sequential stages of cardiogenesis was performed in CCS-lacZ transgenic mice (E9.5 to 15.5). Embryos were stained for ß-galactosidase activity and the myocardial marker HHF35. At early stages CCS-lacZ expression was observed in a ring surrounding the AV canal, which connected at the inner curvature to the primary fold. The first sign of formation of the (CCS-lacZ negative) RV inlet component was a groove in the CCS-lacZ positive tissue of the primary fold. Outgrowth of the RV inlet tract resulted in division of the primary fold in a septal part, the trabecula septomarginalis and a lateral part, the moderator band, which extended laterally up to the right AV ring. Electrophysiological measurements in embryonic hearts (E15.5) in which the right atrium (RA) and RV were isolated from the left atrium (LA) and LV supported the functionality of this AV-connection via the moderator band, by demonstrating sequential atrial and ventricular activation in both RA/RV and LA/LV preparations. In conclusion, our observations may provide a possible morphological and functional explanation for atriofascicular accessory pathways via the moderator band, underlying Mahaim tachycardia.

Key Words: cardiac conduction system • cardiac development • electrophysiology • arrhythmia • Mahaim tachycardia

This article has been cited by other articles:

				N. D. Hahurij, A. C. Gittenberger-De Groot, D. P. Kolditz, R. Bokenkamp, M. J. Schalij, R. E. Poelmann, and N. A. Blom Accessory Atrioventricular Myocardial Connections in the Developing Human Heart: Relevance for Perinatal Supraventricular Tachycardias Circulation, June 3, 2008; 117(22): 2850 - 2858. [Abstract] [Full Text] [PDF]

				D. P. Kolditz, M. C.E.F. Wijffels, N. A. Blom, A. van der Laarse, N. D. Hahurij, H. Lie-Venema, R. R. Markwald, R. E. Poelmann, M. J. Schalij, and A. C. Gittenberger-de Groot Epicardium-Derived Cells in Development of Annulus Fibrosis and Persistence of Accessory Pathways Circulation, March 25, 2008; 117(12): 1508 - 1517. [Abstract] [Full Text] [PDF]

				D. P. Kolditz, M. C.E.F. Wijffels, N. A. Blom, A. van der Laarse, R. R. Markwald, M. J. Schalij, and A. C. Gittenberger-de Groot Persistence of Functional Atrioventricular Accessory Pathways in Postseptated Embryonic Avian Hearts: Implications for Morphogenesis and Functional Maturation of the Cardiac Conduction System Circulation, January 2, 2007; 115(1): 17 - 26. [Abstract] [Full Text] [PDF]