Anatomy of Cardiac Conduction System

1. Anatomy of Cardiac
Conduction System
曹玄明 醫師
陽明大學附設醫院

2. Normal Sinus Rhythm
Click heart to
view animation
*
Animation

3. Impulse Formation In SA
Node

4. Atrial Depolarization

5. Delay At AV Node

6. Conduction Through Bundle
Branches

7. Conduction Through Purkinje
Fibers

8. Ventricular Depolarization

11. Discovery of anatomic
substrates for conduction
1852. Stanius: impulses were conducted
across the atrioventricular junction through
the myocardium in amphibian hearts
1893. His: the presence of a solitary muscle
bundle crossing the fibrous plane of AV
insulation
1893. Kent: found multiple muscular strands
crossing the insulated AV planes

12. 1906. Tawara: clarification of the existence
of a specialized axis: atrioventricular node,
continued as the bundle of His and
terminated in the ventricular Purkinje cells
1907. Keith and Flack: confirm the existence
of AV node and also discover the location of
cardiac pacemaker: sinus node

13. Criterions for the histological definition
of cardiac conduction system
Histological discrete from the adjacent
working myocardium
Serially traceable from section to section
Insulated from the adjacent working
myocardium by a sheath of fibrous tissue

14. Sinus node
The sinus node is located at the junction of
superior caval vein with the right atrium,
spindle shape structure 10-20mm long, 2-
3mm wide and thick
90% cases: it is positioned just inferior to the
crest of the right atrial appendage
10% cases: it extended as a horseshoe
across the crest, reaching into the interatrial
groove

19. In human heart, an extensive area within the
terminal crest adjacent to the node where
nodal cells intermingled with working atrial
myocytes
The paranodal area was separated by short
zone of atrial myocardium from true node
This specialized myocytes is very likely to
generate abnormal rhythm

21. Cells from the SA node region exhibit a wide
variety of morphologies.
Only spindle and spider shaped cells exhibit
a typical electrophysiological characteristics
of pacemaker cell
Presence of hyperpolarization-activated
current, If; and absence of inwardly rectifying
K current, Ik1; and spontaneous beating
under physiological conditions

22. Function of SA node
Sinus node cells function as electrically
coupled oscillators that discharge
synchronously because of mutual
entrainment.
Faster discharging cells area slowed by the
cells firing more slowly
The interaction depends on the degree of
coupling and the EP characteristics of each
sinus nodal cells.

23. Blood supply of SA node
55-60% from RCA
40-45% from LCX

24. Internodal and intraatrial
conduction
Three intraatrial pathways
1. anterior internodal pathway: SA
nodeanterior interatrial band (Backmann
bundle)
2. Middle internodal pathway: SA node 
crest of IAS  AVN
3. posterior internodal tract: SA node crista
terminalis eustachian ridge  IAS above
coronary sinus

26. Interatrial bundles

28. Septum primum
Foramen secundum
Foramen ovale
Septum secundum

29. 1.True septal wall:
flap valve of OF (1.5-2.4
cm2)
2 . Limbus: pronounced
superiorly & laterally
Fusion of septum primum
and secundum
3. Folds, interposed between
the chamber: no the true
septal wall

30. Europace 2007

32. The atrioventricular axis

33. The normal junction area:
(1)Transitional cell zone
(2)Atrioventricular node (compact node):
located at the apex of koch triangle
(3)Bundle of His: distal part of compact AV
node ,perforates central fibrous body and
through the annulus fibrosis

34. AV conduction axis can be segregated into
two connecting compartments based on
immunohistological analyses
(1)Connexin45: compact node and
transitional cell
(2)Coexpressing of connexin43 and
connexin45: His bundle, lower nodal cells
and posterior nodal extension

37. Ho Clin Anat 2009
KOCH Triangle

41. The mean distance from
nodal artery to
endocardium 3.5± 1.5mm
18% patients had
compact node close to the
hinge of TV
Sanchez Quintata JCE 2001
Blood supply and Risk of Nodal Artery
and AV Conduction Tissue Injury

42. Dual AVN and AVNRT

43. Anderson JCE 1999 Ho Circulation 2008

44. Pre-excitation and AP mediated tachycardia

45. Bundle branches
These structures begin at the superior
margin of interventricular septum
Left bundle branch onto the septum
beneath the non-coronary cusp fascicular
system (anterior and posterior)
Right bundle branch  unbranched AV
bundle down the right interventricular
septum  RV apex

46. Trifascicular bundle branch
system

47. Terminal Purkinje fibers
These fibers connect with the ends of the
bundle branches to form networks on the
endocardial surface of both ventricles.
Less concentrated at the base of ventricles
and at the papillary muscle
In human, they penetrate the inner 1/3 of the
endocardium.

49. 謝謝各位聆聽