{"status":"ok","message-type":"work","message-version":"1.0.0","message":{"indexed":{"date-parts":[[2026,10,3]],"date-time":"2026-10-03T08:07:25Z","timestamp":1791014845659,"version":"4.1.0"},"reference-count":57,"publisher":"MDPI AG","issue":"7","license":[{"start":{"date-parts":[[2025,6,26]],"date-time":"2025-06-26T00:00:00Z","timestamp":1750896000000},"content-version":"vor","delay-in-days":0,"URL":"https:\/\/creativecommons.org\/licenses\/by\/4.0\/"}],"content-domain":{"domain":[],"crossmark-restriction":false},"short-container-title":["JCDD"],"abstract":"<jats:p>The anatomical arrangement of the atrioventricular node has been likened to a riddle wrapped up in an enigma. There are several reasons for this alleged mystery, not least the marked variability in structure between different species. Lack of detailed knowledge of the location of the node relative to the atrial and ventricular septal structures has also contributed to previous misunderstandings. Recent studies comparing the findings of gross dissection with virtual dissection of living datasets, combined with access to a large number of serially sectioned human and animal hearts, have served to provide the evidence to solve the riddle. We summarise these findings in this review. We explain how the node is located within the atrial walls of the inferior pyramidal space. It becomes the non-branching component of the atrioventricular conduction axis as the axis extends through the plane of atrioventricular insulation to enter the infero-septal recess of the left ventricular outflow tract. The node itself is formed by contributions from the tricuspid and mitral vestibules, with extensive additional inputs from the base of the atrial septum. We show how knowledge of development enhances the appreciation of the arrangements and offers an explanation as to why, on occasion, there can be persisting nodoventricular connections. We discuss the findings relative to the circuits producing atrioventricular re-entry tachycardia. We conclude by emphasising the significance of the variation of the anatomical arrangements within different mammalian species.<\/jats:p>","DOI":"10.3390\/jcdd12070245","type":"journal-article","created":{"date-parts":[[2025,6,26]],"date-time":"2025-06-26T11:15:23Z","timestamp":1750936523000},"page":"245","update-policy":"https:\/\/doi.org\/10.3390\/mdpi_crossmark_policy","source":"Crossref","is-referenced-by-count":6,"title":["The Anatomy of the Atrioventricular Node"],"prefix":"10.3390","volume":"12","author":[{"ORCID":"https:\/\/orcid.org\/0000-0001-5163-9021","authenticated-orcid":false,"given":"Robert H.","family":"Anderson","sequence":"first","affiliation":[{"name":"Biosciences Division, Newcastle University, Newcastle-upon-Tyne NE2 4HH, UK"}],"role":[{"vocabulary":"crossref","role":"author"}]},{"ORCID":"https:\/\/orcid.org\/0000-0002-5374-8317","authenticated-orcid":false,"given":"Dami\u00e1n","family":"S\u00e1nchez-Quintana","sequence":"additional","affiliation":[{"name":"Department of Human Anatomy and Cell Biology, Faculty of Medicine, University of Extremadura, 06006 Badajoz, Spain"}],"role":[{"vocabulary":"crossref","role":"author"}]},{"ORCID":"https:\/\/orcid.org\/0009-0008-1161-5349","authenticated-orcid":false,"given":"Jorge","family":"Nevado-Medina","sequence":"additional","affiliation":[{"name":"Department of Human Anatomy and Cell Biology, Faculty of Medicine, University of Extremadura, 06006 Badajoz, Spain"}],"role":[{"vocabulary":"crossref","role":"author"}]},{"given":"Diane E.","family":"Spicer","sequence":"additional","affiliation":[{"name":"Heart Institute, Johns Hopkins All Children\u2019s Hospital, St. Petersburg, FL 33701, USA"}],"role":[{"vocabulary":"crossref","role":"author"}]},{"ORCID":"https:\/\/orcid.org\/0000-0001-8926-3752","authenticated-orcid":false,"given":"Justin T.","family":"Tretter","sequence":"additional","affiliation":[{"name":"Division of Pediatric Cardiology, Cleveland Clinic Children\u2019s, and The Heart, Vascular, and Thoracic Institute, Cleveland Clinic, Cleveland, OH 44195, USA"}],"role":[{"vocabulary":"crossref","role":"author"}]},{"given":"Wouter H.","family":"Lamers","sequence":"additional","affiliation":[{"name":"Department of Anatomy & Embryology, Maastricht University, 6211 LK Maastricht, The Netherlands"}],"role":[{"vocabulary":"crossref","role":"author"}]},{"ORCID":"https:\/\/orcid.org\/0009-0007-2224-1090","authenticated-orcid":false,"given":"Zihan","family":"Hu","sequence":"additional","affiliation":[{"name":"Department of Anatomy & Embryology, Maastricht University, 6211 LK Maastricht, The Netherlands"}],"role":[{"vocabulary":"crossref","role":"author"}]},{"ORCID":"https:\/\/orcid.org\/0000-0001-5079-7546","authenticated-orcid":false,"given":"Andrew C.","family":"Cook","sequence":"additional","affiliation":[{"name":"Institute of Cardiovascular Science, University College, London WC1E 6BT, UK"}],"role":[{"vocabulary":"crossref","role":"author"}]},{"ORCID":"https:\/\/orcid.org\/0000-0003-3249-3711","authenticated-orcid":false,"given":"Eduardo Back","family":"Sternick","sequence":"additional","affiliation":[{"name":"Electrophysiology Unit, Biocor Instituto, Nova Lima 34006083, Brazil"}],"role":[{"vocabulary":"crossref","role":"author"}]},{"given":"Demosthenes G.","family":"Katritsis","sequence":"additional","affiliation":[{"name":"Department of Cardiology, Hygeia Hospital, 15123 Athens, Greece"},{"name":"Johns Hopkins Hospital, Baltimore, MD 21287, USA"}],"role":[{"vocabulary":"crossref","role":"author"}]}],"member":"1968","published-online":{"date-parts":[[2025,6,26]]},"reference":[{"key":"ref_1","first-page":"821","article-title":"Re-evaluation of the structure of the atrioventricular node and its connections with the atrium","volume":"22","author":"Anderson","year":"2020","journal-title":"EP Eur."},{"key":"ref_2","doi-asserted-by":"crossref","first-page":"52","DOI":"10.15420\/aer.2020.30","article-title":"The Human Atrioventricular Node: Oedipus and the Riddle of the Sphinx","volume":"9","author":"Katritsis","year":"2020","journal-title":"Arrhythmia Electrophysiol. Rev."},{"key":"ref_3","doi-asserted-by":"crossref","first-page":"e232731","DOI":"10.1148\/radiol.232731","article-title":"Multidimensional analysis of the adult human heart in health and disease using hierarchical phase-contrast tomography","volume":"312","author":"Brunet","year":"2024","journal-title":"Radiology"},{"key":"ref_4","doi-asserted-by":"crossref","unstructured":"Anderson, R.H., Mori, S., Spicer, D.E., Sanchez-Quintana, D., and Jensen, B. (2018). The anatomy, development, and evolution of the atrioventricular conduction axis. J. Cardiovasc. Dev. Dis., 5.","DOI":"10.3390\/jcdd5030044"},{"key":"ref_5","first-page":"455","article-title":"Miniseries 1\u2014Part III:\u2018Behind the scenes\u2019 in the triangle of Koch","volume":"24","author":"Tretter","year":"2022","journal-title":"EP Eur."},{"key":"ref_6","doi-asserted-by":"crossref","first-page":"1430","DOI":"10.1136\/heartjnl-2021-320304","article-title":"Anatomy of the conduction tissues 100 years on: What have we learned?","volume":"108","author":"Anderson","year":"2022","journal-title":"Heart"},{"key":"ref_7","doi-asserted-by":"crossref","unstructured":"S\u00e1nchez-Quintana, D., Cook, A.C., Macias, Y., Spicer, D.E., and Anderson, R.H. (2023). The atrioventricular conduction axis revisited for the 21st century. J. Cardiovasc. Dev. Dis., 10.","DOI":"10.20944\/preprints202311.0014.v1"},{"key":"ref_8","doi-asserted-by":"crossref","unstructured":"Pandozi, C., Matteucci, A., Mariani, M.V., Russo, M., Galeazzi, M., Lavalle, C., Bassi, A., Malacrida, M., and Colivicchi, F. (2025). Features and Electrophysiological Behavior of AV Nodal Structures Potential Recorded in Humans. Heart Rhythm, online ahead of print.","DOI":"10.1016\/j.hrthm.2025.04.010"},{"key":"ref_9","doi-asserted-by":"crossref","first-page":"3","DOI":"10.1007\/978-3-031-44087-8_1","article-title":"Human cardiac development","volume":"1441","author":"Hikspoors","year":"2024","journal-title":"Adv. Exp. Med. Biol."},{"key":"ref_10","doi-asserted-by":"crossref","first-page":"831","DOI":"10.1161\/CIRCULATIONAHA.110.936591","article-title":"Atrioventricular nodal reentrant tachycardia","volume":"122","author":"Katritsis","year":"2010","journal-title":"Circulation"},{"key":"ref_11","doi-asserted-by":"crossref","first-page":"1990","DOI":"10.1016\/j.hrthm.2021.07.065","article-title":"Similarities and differences in the arrangement of the atrioventricular conduction axis in the canine compared to the human heart","volume":"18","author":"Tretter","year":"2021","journal-title":"Heart Rhythm"},{"key":"ref_12","first-page":"443","article-title":"Miniseries 1\u2014Part II: The comparative anatomy of the atrioventricular conduction axis","volume":"24","author":"Tretter","year":"2022","journal-title":"EP Eur."},{"key":"ref_13","doi-asserted-by":"crossref","first-page":"517","DOI":"10.1111\/joa.14066","article-title":"Cardiac development demystified by use of the HDBR atlas","volume":"245","author":"Anderson","year":"2024","journal-title":"J. Anat."},{"key":"ref_14","doi-asserted-by":"crossref","first-page":"43","DOI":"10.1113\/jphysiol.1883.sp000121","article-title":"On the innervation of the heart, with especial reference to the heart of the tortoise","volume":"4","author":"Gaskell","year":"1883","journal-title":"J. Physiol."},{"key":"ref_15","first-page":"14","article-title":"Die Th\u00e4tigkeit des embryonalen Herzens und deren Bedeutung f\u00fcr die Lehre von der Herzbewegung beim Erwachsenen","volume":"14","author":"His","year":"1893","journal-title":"Arb. Med. Klin."},{"key":"ref_16","doi-asserted-by":"crossref","first-page":"233","DOI":"10.1113\/jphysiol.1893.sp000451","article-title":"Researches on the structure and function of the mammalian heart","volume":"14","author":"Kent","year":"1893","journal-title":"J. Physiol."},{"key":"ref_17","doi-asserted-by":"crossref","first-page":"623","DOI":"10.1016\/S0140-6736(01)80227-0","article-title":"The auriculo-ventricular bundle of His","volume":"167","author":"Keith","year":"1906","journal-title":"Lancet"},{"key":"ref_18","unstructured":"Keith, A. (1950). An Autobiography, Philosophical Library."},{"key":"ref_19","unstructured":"Tawara, S. (1906). Das Reizleitungssystem des S\u00e4ugetierherzens. Eine anatomische Studie \u00fcber das Atrioventrikul\u00e4re B\u00fcndel und Die Purkinjeschen F\u00e4den, G. Fischer."},{"key":"ref_20","doi-asserted-by":"crossref","first-page":"359","DOI":"10.1016\/S0140-6736(01)32375-9","article-title":"The auriculo-ventricular bundle of the human heart","volume":"168","author":"Keith","year":"1906","journal-title":"Lancet"},{"key":"ref_21","first-page":"85","article-title":"Weiter Mitteilungen uber den Sinusknoten der Herzens","volume":"13","author":"Koch","year":"1909","journal-title":"Verh. Der Dtsch. Path Anat."},{"key":"ref_22","doi-asserted-by":"crossref","first-page":"210","DOI":"10.1046\/j.1540-8167.2001.00210.x","article-title":"Topographic anatomy of the inferior pyramidal space: Relevance to radiofrequency catheter ablation","volume":"12","author":"Ho","year":"2001","journal-title":"J. Cardiovasc. Electrophysiol."},{"key":"ref_23","doi-asserted-by":"crossref","first-page":"542","DOI":"10.1016\/S0022-5223(19)37919-X","article-title":"The surgical approach to the septal area of the heart based on experiences with 45 patients with Kent bundles","volume":"79","author":"Sealy","year":"1980","journal-title":"J. Thorac. Cardiovasc. Surg."},{"key":"ref_24","unstructured":"Schoenwolf, G.C., Bleyl, S.B., Brauer, P.R., and Francis-West, P.H. (2015). Larsen\u2019s Human Embryology, Elsevier Health Sciences. [5th ed.]."},{"key":"ref_25","first-page":"27","article-title":"Beitrage zur vergleichenden Anatomie des Herzens der Wirbelthiere","volume":"16","year":"1890","journal-title":"Morphol. Jahrb."},{"key":"ref_26","doi-asserted-by":"crossref","first-page":"456","DOI":"10.1136\/heartjnl-2016-310660","article-title":"Development of the atrial septum in relation to postnatal anatomy and interatrial communications","volume":"103","author":"Jensen","year":"2017","journal-title":"Heart"},{"key":"ref_27","doi-asserted-by":"crossref","unstructured":"McAlpine, W.A. (1975). The left ventricle\u2014General considerations. Heart and Coronary Arteries: An Anatomical Atlas for Clinical Diagnosis, Radiological Investigation, and Surgical Treatment, Springer.","DOI":"10.1007\/978-3-642-65983-6_3"},{"key":"ref_28","first-page":"2159","article-title":"Vorl\u00e4ufige mitteilung \u00fcber eine besondere muskelverbindung zwischen der cava superior und dem Hisschen bundel","volume":"56","author":"Thorel","year":"1909","journal-title":"M\u00fcnchen Med. Wchnschr"},{"key":"ref_29","first-page":"3","article-title":"Referat \u00fcber die Herzst\u00f6rungen in ihren Beziehungen zu den Spezifischen Muskelsystemen des Herzens","volume":"14","author":"Aschoff","year":"1910","journal-title":"Verh. Dtsch. Pathol. Ges."},{"key":"ref_30","first-page":"64","article-title":"Beitr\u00e4ge zur normalen und pathologischen Anatomie des Herzens","volume":"14","year":"1910","journal-title":"Verh. Dtsch. Pathol. Ges."},{"key":"ref_31","doi-asserted-by":"crossref","first-page":"204","DOI":"10.1002\/ar.20631","article-title":"Connexin 43 expression delineates two discrete pathways in the human atrioventricular junction","volume":"291","author":"Hucker","year":"2008","journal-title":"Anat. Rec."},{"key":"ref_32","doi-asserted-by":"crossref","first-page":"97","DOI":"10.1002\/ar.1092320111","article-title":"Spatial distribution of \u201ctissue-specific\u201d antigens in the developing human heart and skeletal muscle III. An immunohistochemical analysis of the distribution of the neural tissue antigen G1N2 in the embryonic heart; implications for the development of the atrioventricular conduction system","volume":"232","author":"Wessels","year":"1992","journal-title":"Anat. Rec."},{"key":"ref_33","doi-asserted-by":"crossref","unstructured":"Hikspoors, J.P., Kruepunga, N., Mommen, G.M., K\u00f6hler, S.E., Anderson, R.H., and Lamers, W.H. (2022). A pictorial account of the human embryonic heart between 3.5 and 8 weeks of development. Comm. Biol., 5.","DOI":"10.1038\/s42003-022-03153-x"},{"key":"ref_34","doi-asserted-by":"crossref","first-page":"395","DOI":"10.1161\/01.RES.88.4.395","article-title":"Development of the myocardium of the atrioventricular canal and the vestibular spine in the human heart","volume":"88","author":"Kim","year":"2001","journal-title":"Circ. Res."},{"key":"ref_35","doi-asserted-by":"crossref","first-page":"571","DOI":"10.1161\/01.CIR.94.3.571","article-title":"Atrioventricular junctional tissue: Discrepancy between histological and electrophysiological characteristics","volume":"94","author":"McGuire","year":"1996","journal-title":"Circulation"},{"key":"ref_36","doi-asserted-by":"crossref","first-page":"362","DOI":"10.1016\/j.jacep.2019.12.004","article-title":"Variable arrangement of the atrioventricular conduction axis within the triangle of Koch: Implications for permanent His bundle pacing","volume":"6","author":"Cabrera","year":"2020","journal-title":"JACC Clin. Electrophysiol."},{"key":"ref_37","doi-asserted-by":"crossref","first-page":"e12","DOI":"10.15420\/aer.2024.13","article-title":"Anatomical ablation of the atrioventricular node","volume":"13","author":"Katritsis","year":"2024","journal-title":"Arrhythmia Electrophysiol. Rev."},{"key":"ref_38","first-page":"464","article-title":"Miniseries 1\u2014Part IV: How frequent are fasciculo-ventricular connections in the normal heart?","volume":"24","author":"Tretter","year":"2022","journal-title":"EP Eur."},{"key":"ref_39","doi-asserted-by":"crossref","first-page":"651","DOI":"10.1016\/0002-8703(47)90080-X","article-title":"Kent\u2019s fibers and the AV paraspecific conduction through the upper connections of the bundle of His-Tawara","volume":"33","author":"Mahaim","year":"1947","journal-title":"Am. Heart J."},{"key":"ref_40","doi-asserted-by":"crossref","first-page":"232","DOI":"10.1016\/0002-9149(73)91036-9","article-title":"Atrioventricular and intraventricular conduction: Revised nomenclature and concepts","volume":"31","author":"Hecht","year":"1973","journal-title":"Am. J. Cardiol."},{"key":"ref_41","first-page":"27","article-title":"Ventricular preexcitation. A Propos. Nomencl. Its substrates","volume":"3","author":"Anderson","year":"1975","journal-title":"Eur. J. Cardiol."},{"key":"ref_42","doi-asserted-by":"crossref","first-page":"1057","DOI":"10.1046\/j.1540-8167.2003.03206.x","article-title":"Fasciculoventricular pathways: Clinical and electrophysiologic characteristics of a variant of Pre-excitation","volume":"14","author":"Sternick","year":"2003","journal-title":"J. Cardiovasc. Electrophysiol."},{"key":"ref_43","first-page":"euad050","article-title":"Evidence for concealed fasciculo-ventricular connections as revealed by His bundle pacing","volume":"25","author":"Mahmud","year":"2023","journal-title":"EP Eur."},{"key":"ref_44","doi-asserted-by":"crossref","first-page":"647","DOI":"10.1016\/j.hrthm.2024.01.003","article-title":"Correction of bundle branch block by so-called nonselective His bundle pacing: The potential role of accessory connections in the ventricular septal crest","volume":"21","author":"Mahmud","year":"2024","journal-title":"Heart Rhythm."},{"key":"ref_45","doi-asserted-by":"crossref","first-page":"233","DOI":"10.1093\/oxfordjournals.eurheartj.a061642","article-title":"Tachycardia caused by an accessory nodoventricular tract: A clinico-pathologic correlation","volume":"5","author":"Gmeiner","year":"1984","journal-title":"Eur. Heart J."},{"key":"ref_46","doi-asserted-by":"crossref","first-page":"3097","DOI":"10.1111\/jce.14247","article-title":"Unusual variants of pre-excitation: From anatomy to ablation. Part III\u2014Clinical presentation, electrophysiologic characteristics, when and how to ablate nodoventricular, nodofascicular, fasciculoventricular pathways, along with considerations of permanent junctional reciprocating tachycardia","volume":"30","author":"Correa","year":"2019","journal-title":"J. Cardiovasc. Electrophysiol."},{"key":"ref_47","doi-asserted-by":"crossref","first-page":"155","DOI":"10.1111\/joa.13179","article-title":"Histological examination of the potential arrhythmic substrates in the setting of Ebstein\u2019s malformation","volume":"237","author":"Cabrera","year":"2020","journal-title":"J. Anat."},{"key":"ref_48","doi-asserted-by":"crossref","first-page":"291","DOI":"10.1016\/0002-9149(74)90292-6","article-title":"Demonstration of dual atrioventricular nodal pathways in man","volume":"33","author":"Rosen","year":"1974","journal-title":"Am. J. Cardiol."},{"key":"ref_49","first-page":"1231","article-title":"Classification of electrophysiological types of atrioventricular nodal re-entrant tachycardia: A reappraisal","volume":"15","author":"Katritsis","year":"2013","journal-title":"EP Eur."},{"key":"ref_50","first-page":"1596","article-title":"Spatial characterization of the tachycardia circuit of atrioventricular nodal re-entrant tachycardia","volume":"23","author":"Katritsis","year":"2021","journal-title":"EP Eur."},{"key":"ref_51","doi-asserted-by":"crossref","first-page":"1396","DOI":"10.1111\/j.1540-8167.1997.tb01036.x","article-title":"Architecture of the atrial musculature in and around the triangle of Koch: Its potential relevance to atrioventricular nodal reentry","volume":"8","author":"Davies","year":"1997","journal-title":"J. Cardiovasc. Electrophysiol."},{"key":"ref_52","doi-asserted-by":"crossref","first-page":"801","DOI":"10.1161\/01.RES.8.4.801","article-title":"Spread of activity through the atrioventricular node","volume":"8","year":"1960","journal-title":"Circ. Res."},{"key":"ref_53","doi-asserted-by":"crossref","first-page":"909","DOI":"10.1161\/01.RES.35.6.909","article-title":"A combined morphological and electrophysiological study of the atrioventricular node of the rabbit heart","volume":"35","author":"Anderson","year":"1974","journal-title":"Circ. Res."},{"key":"ref_54","doi-asserted-by":"crossref","first-page":"1102","DOI":"10.1161\/01.RES.0000101913.95604.B9","article-title":"Site of origin and molecular substrate of atrioventricular junctional rhythm in the rabbit heart","volume":"93","author":"Dobrzynski","year":"2003","journal-title":"Circ. Res."},{"key":"ref_55","doi-asserted-by":"crossref","first-page":"336","DOI":"10.1002\/ar.1092240303","article-title":"Atrioventricular node and input pathways: A correlated gross anatomical and histological study of the canine atrioventricular junctional region","volume":"224","author":"Racker","year":"1989","journal-title":"Anat. Rec."},{"key":"ref_56","doi-asserted-by":"crossref","unstructured":"S\u00e1nchez-Quintana, D., Mac\u00edas, Y., Nevado-Medina, J., Spicer, D.E., and Anderson, R.H. (2024). The atrioventricular conduction axis in man and mouse. J. Cardiovasc. Devel Dis., 11.","DOI":"10.20944\/preprints202410.0169.v1"},{"key":"ref_57","doi-asserted-by":"crossref","first-page":"1591","DOI":"10.1161\/01.CIR.103.11.1591","article-title":"Impaired conduction in the bundle branches of mouse hearts lacking the gap junction protein connexin40","volume":"103","author":"Potse","year":"2001","journal-title":"Circulation"}],"container-title":["Journal of Cardiovascular Development and Disease"],"original-title":[],"language":"en","link":[{"URL":"https:\/\/www.mdpi.com\/2308-3425\/12\/7\/245\/pdf","content-type":"unspecified","content-version":"vor","intended-application":"similarity-checking"}],"deposited":{"date-parts":[[2025,10,9]],"date-time":"2025-10-09T17:59:13Z","timestamp":1760032753000},"score":1,"resource":{"primary":{"URL":"https:\/\/www.mdpi.com\/2308-3425\/12\/7\/245"}},"subtitle":[],"short-title":[],"issued":{"date-parts":[[2025,6,26]]},"references-count":57,"journal-issue":{"issue":"7","published-online":{"date-parts":[[2025,7]]}},"alternative-id":["jcdd12070245"],"URL":"https:\/\/doi.org\/10.3390\/jcdd12070245","relation":{},"ISSN":["2308-3425"],"issn-type":[{"value":"2308-3425","type":"electronic"}],"subject":[],"published":{"date-parts":[[2025,6,26]]}}}