SPECIAL REVIEW 6 Journal of Cardiac Electrophysiologist (PartI) Ventricular Anatomyforthe net of gelatinous fiber at the sub- of sub-endocardium the at fiber gelatinous of net conduction systemofthe Historical sequenceofdiscovery ofthe hypothetical answersareproposed. and presented is issues these of understanding Current formulated. are system conduction the of anatomy the on questions some that after anatomy, basic its and system conduction the of understanding findings ofconductionsystems. siologists. electrophy for contents important still are level, macroscopic a at system conduction the of disposition the and axis conduction major the of features morphologic key summarizing system, conduction mechanisms. electrophysiologic to compared studied less far are heart the in stimulation electrical of conduction Introduction The Czech Jan Evangelista Purkynje discovered a discovered Purkynje Evangelista Jan Czech The the on sequence historical the illustrates review This abnormal or normal of substrates Anatomic Key words: morphology ofconductionsystemandbasicanatomythesystem. historical sequenceofdiscoverythemorphologyconductionsystem,currentorpastissueson Anatomy oftheconductionsystemforelectrophysiologistsisreviewedintwoparts. This firstpartdetailsthe ABSTRACT Arrhythmia 2,3 There is a Korean study on the histological the on study Korean a is There 1 Studies on the pathology of the cardiac the of pathology the on Studies ■ conduction systemofheart 4 ■ arrhythmia ■ discovery in Czech in 1839 and in English in 1845. in English in and 1839 in Czech in discovery his published and heart ungulate the in ventricles conduction bundles (Kent bundle) in addition to the to addition in bundle) (Kent bundles conduction atrioventricular several described he but well, as ventricles and atria between connection muscular the described Kent independently. conduction myogenic described also Britain from Kent dogma. the was time that at which conduction), (neurogenic nerve through than rather conduction) (myogenic muscle through contraction cardiac of propagation the explained and bundle) (His bundle atrio-ventricular the . ventricular or atria the at fibers conducting fast with cells vacuolated are cells Purkinje that understood generally is it but fibers, or cells Purkinje define to how on remains disagreement now Till contraction. cardiac during cells Purkinje of significance the heart. the of kind a as interpreted strangely were features histological its and significance functional or cow),notahumanheart.Littlewasknownaboutits (horse ungulate an of heart the concerned finding His Purkinje network In 1893, Wilhelm His Jr. from Leipzig discovered Leipzig from Jr. His Wilhelm 1893, In 5 Tawara in 1906 was the first to re-discover to first the was 1906 in Tawara 울학 과학병리학교실 의과대학 서울대학교 5 In the same year, A.F. Stanley A.F. year, same the In ‘ cartilage 서정욱 ’ in 5 His bundle. The nodes and bundles observed by Kent Some questions REVIEW are now understood to be remnants of atrioventricular ring tissue rather than an aberrant connection in the The historical question "Why does the heart beat?" Wolff-Parkinson-White syndrome. was answered by Tawara, Keith and Flack.4,6 The next In 1906, Sunao Tawara reported his historical question was on the position of the conduction SPECIAL discovery of the AV node in an absolutely perfect pathway in a congenitally malformed heart, description. He was a Japanese physician, who particularly in the heart with an abnormal looping graduated from Tokyo University in 1901 and worked such as a congenitally corrected transposition.7,8 The with Ludwig Aschoff in Germany from 1903. His expression of ganglion nodosum, which is like an achievements were appreciated by cardiologists not antigen in the conduction system, was discovered by only for his AV node discovery, but also for his the Amsterdam group during immuno-histochemical integration of previous knowledge about the studies on the molecular expression of liver.9,10 They conduction system by His and Purkinje. Tawara realized that tracing the conduction system at the explained how the His bundle expands and how it embryonic heart could reveal developmental branches into the left and right bundles as described processes of the human heart. Studies on cell to cell by Purkinje. One year after Tawara’s discovery, Sir communication like gap junction proteins and on Arthur Keith and his young medical student Martin functional development of myofilaments followed.11,12 Flack discovered the sinus node in the heart of several The development of electro-physiologic techniques species at an area that histologically resembled the to evaluate the mechanism of arrhythmia left the Tawara’s node. In 2007, the centennial discovery of question on the cellular mechanism of the abnormal the sinus node by Keith and Flack was celebrated.1,6 excitation of the heart10 unanswered. This question is

Figure 1. The septal surface of the right after removal of the free anterior wall. The his bundle starts from the (AVN) and runs inferior to the border of the membranous septum (MS) and continues to the right bundle branch (arrows) underneath the medial papillary muscle (MPM) and the septomaginal trabeculation. CS; orifice of coronary sinus, RCA; right coronary artery, RVO; right ventricular outflow, SEP; septal leaflet of , VIF; ventriculo-infundibular fold

VOL.11 NO.1 7 SPECIAL REVIEW 8 Journal of Cardiac Basic Anatomy cell. Purkinje the of significance functional and nature the about myocardial infarctwitharrhythmia. as such conditions heart pathologic other some and arrhythmia atrial to relation in system conduction cardiac the of pathology the in studied recently demonstrates its location at the inferior border of the of border inferior the at location its demonstrates which defects, septal ventricular with heart the of anatomy surgical for documented is axis conduction morphology. its of irrespective system conduction peripheral the describing used is term vague a occasions other in but branch, bundle left the as to referred are cells Purkinje Sometimes, network. Purkinje the or cardiomyocytes Purkinje about talk others but fibers, Purkinje term the use physicians Some heart. human the in seen not are they that upon agreed is It heart. ungulate the in found sub-endocardium ventricular the ALPM; antero-lateralpapillarymuscle,CS;coronarysinus,LAD;leftanteriordescendingartery,PMPM;postero-medial and muralleafletofmitralvalve.Awedgefibroadiposetissueinterposesattheatrioventricularjunction. Figure 2. One major group of questions left unanswered is unanswered left questions of group major One The landmark of the right ventricular aspect of the of aspect ventricular right the of landmark The Arrhythmia Left ventricularseptalsurfaceandanteriormitralleaflet(AML)afterremovalofthefreewallleftventricle 3 14 Purkinje cells are vacuolated cells at cells vacuolated are cells Purkinje 13 starts from the apex so that the ventricles squeeze ventricles the that so apex the from starts contraction the but apex, the to down spreads and Muscle dissection an aberrantconnection(Figure3). for potential a having connected, are walls ventricular and atrial left the where wall free a has 1/4 lateral the but valve, aortic the of cusp non-coronary the and cusp left the with continuity fibrous in is leaflet mitral anterior the of 3/4 medial The leaflet. mitral anterior the and valve aortic the of cusp non-coronary the beneath lies which septum, membranous the of border inferior the from arises bundle left The 2). (Figure leaflet mitral anterior the with relation close a has marginalis oftherightventricle. septo- trabecula the underneath myocardium the at localized also is branch bundle right the of location The type. peri-membranous a of defects septal ventricular with of border inferior the at and 1), (Figure heart normal a of septum membranous Conduction starts from the base of the ventricles the of base the from starts Conduction system conduction the of aspect ventricular left The papillary muscle REVIEW

cs SPECIAL

LV Septum

Figure 3. Close up of the specimen Fig 2. after lifting up the anterior mitral leaflet to show the and the ventricular surface of the mitral anterior leaflet seen from the apex of the left ventricular cavity. Mitral-aortic fibrous continuity is observed between the left and non-coronary cusps and the anterior part of mitral anterior leaflet (dotted line). The posterior part of the mitral leaflet is attached both to the left and left ventricle (line). Arrows indicate the anterior and posterior sub-branches of the left bundle branch. LC; left coronary cusp, MS; membranous septum, NC; non-coronary cusp, RC; right coronary cusp

Figure 4. After removal of the epicardium and fatty tissue, we can see the direction of fiber bundles, which make whorls in the apex. LAD; left anterior descending coronary artery, LV; left ventricle, RV; right ventricle.

VOL.11 NO.1 9 SPECIAL REVIEW 10 Journal of Cardiac II. part in discussed be will network Purkinje and system conduction the of nature molecular functional and 1. Boyett MR,DobrzynskiH.Thesinoatrialnode isstillsettingthe References called system conduction peripheral the to connect to apex the to run They branches. bundle left and right and bundle His the node, Atrioventricular the of consists Conclusion Purkinje network(Figure5). area septal the of current counter a through apex the at U-turn a form branches bundle right and left the if arises question the Then 4). (Figure principle this confirms level macroscopic at muscle cardiac the of Dissection apex. the from 2. Davies MJ.Pathologyofconducting tissueoftheheart.London: ventricle hasafiberdirectioninparalleltothelongaxisofheart. Figure 5. pace 100yearsafteritsdiscovery. 1545. The cardiac conduction system of ventricles of system conduction cardiac The ‘ Purkinje network Purkinje Arrhythmia Further dissectionoftheventricularseptumshowsgradualchangetheirdirection.Thefreewallleft ’ ’ . The histological details histological The . s bundle branch and the and branch bundle s Circ Res Circ . 2007;100:1543- 4. Seo JW,ChiJG,LeeSK.Cardiacconductionsystem- 3. Davies MJ,AndersonRH,BeckerAE.Theconductionsystemof 6. Silverman ME,HollmanA.DiscoveryofthesinusnodebyKeith 9. Wessels A,VermeulenJL,VerbeekFJ,ViraghS,KalmanF,Lamers 5. James TN.Thedevelopmentofideasconcerningtheconduction 10. 7 .Lev M,FieldingRT,ZaeskeD.MixedLevocardiawithVentricular 8. Anderson RH.Theconductiontissues incongenitallycorrected Block. AHistopathologicStudyoftheConductionSystem. Inversion (CorrectedTransposition)withCompleteAtrioventricular Morphological observationsontheautopsycases. the heart.London:Butterworths,1983. Butterworths, 1971. and Flack:onthecentennialoftheir1907publication. development oftheatrioventricularconductionsystem. tissue antigenG1N2intheembryonicheart;implicationsfor An immunohistochemicalanalysisofthedistributionneural antigens inthedevelopinghumanheartandskeletalmuscle.III. WH, MoormanAF.Spatialdistributionof"tissue-specific" system oftheheart. 1992;232:97-111. 2007;93:1184-1187. transposition. Cardiol Pathol 886. substrates forcardiacconduction. Moorman AF,ChristoffelsVM,Anderson RH.Anatomic . 1983;17:127-137. . 1963;12:875-883. Ann Thorac Surg Thorac Ann Ulster Med J Med Ulster . 2004;77:1881-1882. . 1982;51:81-97. Heart Rhythm Heart . 2005;2:875- Anat Rec Anat Korean J Korean Heart Am J Am . . 11 .Davis LM, Rodefeld ME, Green K, Beyer EC, Saffitz JE. Gap 13. de Bakker JM, van Rijen HV. Electrocardiographic manifestation REVIEW junction protein phenotypes of the human heart and conduction of anatomical substrates underlying post- system. J Cardiovasc Electrophysiol. 1995;6:813-822. tachycardias. J Electrocardiol. 2007;40:S21-25. 12. van Kempen MJ, Fromaget C, Gros D, Moorman AF, Lamers 14. Di Maio A, Ter Keurs HE, Franzini-Armstrong C. T-tubule profiles WH. Spatial distribution of connexin43, the major cardiac gap in Purkinje fibres of mammalian myocardium. J Muscle Res Cell SPECIAL junction protein, in the developing and adult rat heart. Circ Res. Motil. 2007;28:115-121. 1991;68:1638-1651.

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