left and right anatomy with special reference to electrophysiology

1. RT & LT ATRIAL ANATOMY WITH SPECIAL
REFERENCE TO ELECTROPHYSIOLOGY
KAPIL R
DEPT OF CARDIOLOGY

2. RIGHT ATRIUM
Venous
component
SVC/IVC/CS
Appendage
Body
Vestibule
> smooth muscular
wall around the
tricuspid orifice
> TV leaflet support
> Surrounded by
pectinate muscle

3. ELECTROANATOMICAL LANDMARKS
Terminal Crest (Crista Terminalis)
SA node
Koch’s triangle
Inferior pyramidal space
Cavotricuspid isthmus
Eustachian ridge
The Sub-Eustachian Sinus (Sinus of Keith, Sub-
Thebesian Recess)

4. TERMINAL CREST
• Demarcates junction between
appendage and venous component.
• Important anatomic landmark due to
its close association with the sinus
node region and the origin of the
pectinate muscles .
• TC - C-shaped ridge of muscle SV
& p. RA

5. • Demarcates the limit
between the smooth wall
of the vein and the
rough wall of the
appendage acting as a
natural barrier to the
cardiac conduction
system.
• From the lateral margin
of the crest arises a
series ofmuscle
bundles pectinate
muscles, which fan out
from the crest toward
the vestibular portion

6. MYOFIBER ORIENTATION
• The myocytes in the TC are
mostly aligned along the
long axis of the muscle
bundle, thus favoring
preferential conduction.
• myocytes in the intercaval
area, outside the crista
terminalis, are aligned
obliquely- sudden change in
orientation represents a
great substrate for atrial
arrhythmia .

7. Crescent-shaped or cigar-
shaped structure usually lodged
immediately subepicardially
within the sulcus terminalis,
lying just inferior to the crest of
the atrial appendage.
• Imp: approaching from the
endocardial surface requires
more RF energy to ablate the
sinus node
SA nodal A.  55 % RCA / 45 %LCX
SA NODE

8. INTRAMYOCARDIAL
EXTENSIONS
• Nodal extensions (arrows)
to superior caval vein,
terminal crest, and
epicardium
• SA node modification RFA –
IST

9. TRIANGLE OF KOCH
• posteriorly - a fibrous extension from
the Eustachian valve called the tendon
of Todaro.
• anterior - (annulus) of the septal
leaflet of TV.
• apex - central fibrous body (CFB) of
the heart where the His bundle
penetrates.
• inferior –CSO + vestibule
immediately anterior to it.
• vestibular portion - ablation of the
slow path AVNRT
• Fast pathway - area of musculature
close to the apex of the triangle

10. FLUOROSCOPY

11. Toward the inferior portion of the triangle, there are extensions of nodal
tissues that extend inferiorly to the right and left toward the TV & MV
respectively  slow pathway conduction. Because this area also
contains the zone of transitional cells that feeds into the compact AV
node, this too may have a role in slow pathway conduction.

12. Multicomponent atrial electrograms and “slow pathway potentials-
target sites RFA of the slow pathway in patients with AVNRT.
Low amplitude with fractionated electrograms in the base of the
triangle of Koch near the coronary sinus and anterior aspects of
the tricuspid annulus is now the key guidance to identify the slow
pathway area

16. INFERIOR PYRAMIDAL SPACE
The course of the artery to the AV node through the inferior pyramidal
space and toward the central Žfibrous body. When viewed from the right
atrial cavity, the triangle of Koch overlies the inferior pyramidal space

17. In this septal isthmus, the most inferior part of the atrioventricular
septum, the IPS is sandwiched between the musculature of theright
atrium (RA) and the crest of the muscular interventricular septum (IVS).
The atrioventricular nodal artery(the white arrow) is contained in the IPS
just anterior to the CS os

18. LAO 37
HR
A
C
S
R
V
HI
S
IV
S
CS
OS

19. RAO 30HRA
RV
C
S
HI
S

20. CTI- cavotricuspid isthmus
• CTI- lower part of the RA between the ICV and TV  conduction delay  rentrant circuit
( CTI dependent or typical or counterclockwise A. flutter)
• AnteriorlyTV annulus / posteriorly- Eus. valve

21. Ablation catheter is advanced to RV(RAO ) the tip is deflected to achive contact with RV
inferior wall and withdrawn progressively until it records small atrial and large venticular
electrograms . Distal tip of the catheter is then adjusted in LAO until it is midway on the CTI
between atrial septum and RA lateral wall towards 6’O clock in LAO 45

22. 1-Paraseptal isthmus- the base of
Koch’s triangle( septal isthmus)-
close to AV node(inf. ext) / thickest
2-Inferior (central)- thinnest
ablation site bet. IVC orifice and
TV annulus
3.Inferolateral
RAO projection – RA wall opened

23. EUSTACHIAN RIDGE
• EP  RA via the inferior route - 1st
structure encountered is the Eustachian
valve (EV) guarding the orifice of the ICV.
• Normal- thin, insignificant, crescentic flap.
• Large flap impede access to the most
posterior part of the isthmus.
• The free border of the EV continues as
the tendon of Todaro that runs in the
musculature of the Eustachian ridge
• In patients with a large Eustachian
ridge/valve, paraseptal isthmus block
can be obtained only after the
complete ablation of the enlarged
Eustachian ridge

24. SUB-EUSTACHIAN SINUS (SINUS OF
KEITH, SUB-THEBESIAN RECESS)
• an extension (20%) of a pouch-like isthmus
under the orifice of the coronary sinus.
• Local radiofrequency delivery may be
impaired by this structure because an area of
limited blood flow results in delayed catheter
tip cooling.
• Preprocedural planning, where the presence
of a large pouch would dictate a central
approach to the ablation
• considerable difficulty in achieving a complete
line of block in isthmus -alternative right
atrium isthmus line instead

25. INTER ATRIAL SEPTUM
• The true septum, as defined by the area that can be excised
without exiting the heart, is limited to the area marked by the
valve of the oval fossa (the embryonic septum primum) and the
anterior buttress of the atrial septum that is the true “secondary
septum” .
• The superior rim of the fossa is an infolding and is not strictly
“septal.”
• Two main anatomic variants of the interatrial septum are
lipomatous hypertrophy of the septum and large septal
aneurysm

26. • True IAS -oval fossa - a depression in the right atrial side of septum
• The rest of muscular rim of the IAS - invagination of the R&LA myocardia separated by vascularized
fibrofatty tissues of the extracardiac fat.
• “Interatrial groove” rather than muscular IAS - a concept that is very important during percutaneous
interventions because
Transseptal punctures through the IAS to access the LA should
be delimited to the boundary of the oval fossa
inadvertent puncture throughout the interatrial groove (muscular IAS) –hemopericardium( highly
anticoagulated patient ) - blood will dissect the vascularized fibrofatty tissue that is sandwiched
between R&LA wall

27. • LHS-accumulation of fat in the interatrial groove not in the true
septum
• Increased size of the atrial chambers (e.g., increased age or body
mass), severe kyphoscoliosis, LVH, or an enlarged aorta can affect
the orientation of the septal plane and may result in displacement of
the oval fossa
• The risk of perforating the heart is higher in such cases when
attempting to circumvent the barrier by puncturing the peripheral of
the true septum.
Pre – procedural evaluation before transeptal EP studies

28. IAS is not a standard target site for RFA
Focal activation pattern from IAS  BB
FAP’s

31. RAO 30

32. LAO 30

33. LEFT ATRIUM
Venous
Component
Body
AppendageVestibule

34. ELECTROANATOMICAL LANDMARKS
Myoarchitecture
Pulmonary Veins
Left Atrial Ridge
Left Atrial Appendage
Left Atrial Isthmus

35. UNPROTECTED AREA OF PERFORATION
• lateral wall - 2.5 and 4.9 mm /
anterior wall, related to the aortic
root, ranges from 1.5 to 4.8 mm
(mean, 3.31.2 mm) thick
• very thin at the area near the
vestibule of the mitral annulus
diminishing to an average
thickness of 2 mm.

36. Area of the anterior wall just behind the aorta that is
exceptionally thin- McAlpine area “unprotected” area
at risk of perforation

37. The coronary sinus, with its continuation, the great cardiac vein,
runs along the epicardial aspect of the posteroinferior region

38. TRUE IAS
• The major part of the endocardial LA
including the septal wall and interatrial
groove component is relatively smooth.
• The smoothest parts are the superior
and posterior walls, which make up the
pulmonary venous component and the
vestibule surrounding the mitral orifice.
• Behind the posterior wall of the
vestibular component of the LAis the
anteriorwall of the coronary sinus

39. MYOARCHITECTURE - LEFT ATRIUM- BACHMAN & SEPTOPULMONARY BUNDLE
• Subepicardial - fibers in the anterior wall- main bundle parallel to AV
groove-continuation of the interatrial bundle (Bachmann bundle) 
traced rightward to junction between the RA & SVC

40. Longitudinal fibers of the septopulmonary bundle (PAPEZ bundle )
which arises from the interatrial groove underneath Bachmann’s bundle,
fanning out to line the pulmonary veins and to pass longitudinally over
the dome and in the posterior wall of the left atrium.

41. • Role of structural discontinuities and
heterogeneous fiber orientation favoring
anatomic re entry or anchoring rotors
• The posterior wall of the LA seems important
role in maintaining AF

43. Previous - electrical
isolation of the PVs by
creating circumferential
ablation lines around the
individual or bilateral PV
ostia.
Current  atrial tissue
located in the VA junctions
non-PV trigger points for
AF are located in the
venoatrial junctions
Pulmonary stenosis

44. • At the level of the venoatrial junction, myocardial fibers crossing
the isthmus or carina between the superior and inferior venous
orifices in both right and left PVs .
• The carina appears particularly important in the
development of AF and must be considered in developing the
optimal ablation strategy in many patients.
• Most triggers for initiating AF appear to originate from PV carina
which may imply isolation of contiguous vessels froma single or
circumscribed region to achieve complete PV electrical
disconnection

45. LEFT LATERAL RIDGE
• left lateral ridge between the ostium of the left atrial appendage and
the orifice of the left superior pulmonary vein
• Shape & size important  encircling LT pv isolation &
extrapulmonary vein triggers

46. Oblique vein of LT atrium of MARSHALL(remnant of LT SVC)
subepicardially + rich autonomic fibers  muscular connections
to LT PV’s  electrical substrate- Hwang et al

47. LEFT ATRIAL ISTHMUS
• MITRAL ISTHMUS- inferior margin of the ostium of the left inferior
PV and the mitral annulus increase success rate of catheter
ablation in patients with persistent or long-standing/permanent AF
and prevent macroreentry around the mitral annulus or the left PVs
• Wittkampf et al. - muscle sleeve around CS & close anatomic
proximity of LCX  major anatomic determinants for the creation of
mitral isthmus conduction block

48. LAA- pectinate & extra pectinate
• Triggering AF in 27% of patients
• cactus (30%), chicken wing (48%)
less likely embolic, windsock
(19%), and cauliflower (3%).
• Pectinate trabeculations(arrythmic)
– cauliflower ( highest) Chicken –
less .
• LAA exclusion
Chicken WingCauliflower
Wind sock

49. • Extra pectinate muscle
trabeculations extending inferiorly
from the appendage to the
vestibule of the mitral valve.
• Areas between the muscular
trabeculae and the atrial wall
become exceptionally thin (0.5 ±
0.2 mm), increasing the risk
of cardiac perforation during ablation

50. 3 targets in AF
1-ANTRAL PULMONARY VEIN
ISOLATION
2.COMPLEX FRACTIONATED
ELECTROGRAMS-
low-voltage electrograms (0.05–
0.25 mV) with a cycle length<120
ms, displaying two or more
deflections or having
a continuous deflection from
baseline
3.LINEAR LESIONS- ROOF &
MITRAL ISTHMUS

51. PULMONARY VEINS
• Musculature of the LA wall outer surface
of venous wall ( sleeves -upper veins )
• Sleeves - thicker- surround the veins at the
venoatrial junctions( musculature –thin )
• At the venoatrial junction the myocytes cross
the interpulmonary isthmus or carina at the
subepicardium and the subendocardium
aspects connect the walls of adjacent PVs .
• Variants – RMPV / LT conjoined vein

52. • Peripheral margins - sleeves – high
fibrosis & degeneration
• The arrangement of the myocyte
bundles within the sleeves there
appeared to be a meshlike arrangement
of muscle fascicles, made up of
circularorientated bundles that
interconnected with bundles that ran in
longitudinal or obliquely orientation-
microrentry and arrhythmias .

53. THE NEIGHBOURHOOD
• Esophagus – perforation
• Periesophageal Vagus Nerves- pyloric spasm
• Phrenic Nerves
• INTRINSIC LEFT ATRIAL INNERVATION - ganglion cells
in a fat pad adjacent to the epicardium of the right PVs-
negative chronotropic effects junction between the inferior
RA & IVC mediate AV conduction slowing
Thank U…..