How to Identify the Conduction How to Identify the Conduction Gaps in the Atrial Flutter using Gaps in the Atrial Flutter using

Non-Contact MappingNon-Contact Mapping

Jin-Long Huang, MD, Ph D.

Cardiovascular Center, Taichung-Veterans General Hospital

National Yang-Ming University, Taipei, Taiwan

Right Atrial Flutters (AFL)

• Typical AFL

• Atypical AFL

Reentry Circuit of Common Atrial Flutter

Morady F. N Engl J of Med. 1999;340:534-544.

ECG Comparison

Counterclockwise Clockwise

Singer: Interventional Electrophysiology. Williams & Wilkins 1997; 356.

positive inferiorly and in V6, and negative in lead V1.

A new electrocardiographic algorithm to differentiate upper loop re-entry from reverse typical atrial flutter

Yuniadi Y, Tai CT,Huang JL,Chen SA.

J Am Coll Cardiol. 2005 Aug 2;46(3):524-8

Reverse typical AFL

Upper Loop AFL

Typical AFL (CCW)

Typical AFL (CW)

Oblique View of Right Atrium

Crista Terminalis

Pectinate Muscle

Orifice of Coronary Sinus

Superior Vena Cava

Fossa Ovalis

Eustachian Ridge

Inferior Vena Cava

Netter F. Atlas of Human Anatomy. 1989;Plate 208.

Catheter Location for Atrial Flutter Ablation

Free wall

Crista

Used with permission of Dr. Brian Olshansky.

Cosio FG. Am J Cardiol. 1993; 71:705-709.

Atrial Flutter Ablation

Isthmus Conduction Block

Singer: Interventional Electrophysiology. Williams & Wilkins 1997; 367.How do you know isthmus block ??

Characteristic of Unipolar Electrogram

Characteristics of Virtual Unipolar Electrograms for Detecting Isthmus Block

During RF Ablation of Typical AFL Lin YJ et al. J Am Coll Cardiol 2004;43:2300–4.

• The 2nd component of unipolar electrograms represents the approaching wavefront in the RA opposite the pacing site.

• We hypothesized that the morphologic characteristics of the second component of double potentials would be useful in detecting complete CTI block.

Group I (n=37):complete bidirectional CTI blockDuring CS pacing, the second component of unipolar electrograms showed an R or Rs pattern.

A

B

C

D

A

B

C

D

Group II (n = 12) had incomplete CTI block. The second component of unipolar electrograms showed an rS pattern.

A

D

C

B

A

D

C

B

Group III (n= 3) had complete CTI block with transcristalconduction. The second component of unipolar electrograms showed an rSR pattern.

A

C

D

B

A

C

D

B

Conclusions

A predominant R-wave pattern in the secondcomponent of unipolar double potentials at the ablation line indicates complete CTI block, even in the presence of transcristal conduction.

High Resolution Mapping around the Eustachian Ridge(ER) during Typical Atrial Flutter

Huang JL et al J Cardiovasc Electrophysiol. 2006 ;17(11):1187-92.

• 53(M/F= 43/10, 62±14 yrs) with typical AFL.

• The high-resolution mapping of the RA using a

noncontact mapping system during AFL and

pacing from the CS was performed to evaluate the

conduction through the ER.

A (AFL)

a b c

a b c

B(CS Pacing)

Type I pattern: ER block

A (AFL)

a b c

abc

B(CS Pacing)

abc

Type II pattern: Block in AFL and Conduction in CS pacing

A (AFL)

a

SV

b

SV

c

abc

SV

B(CS Pacing)

SV

SVSV

abc

Type III pattern

ResultsThree types of activation patterns around the ER

1. Type I (n=21) exhibited conduction block in the ER during AFL and

CS pacing.

2. Type II (n=8) exhibited conduction block in the ER during AFL, but

conduction through the ER during CS pacing.

3. Type III (n=24) exhibited an activation wavefront that passed along

the ER, with the sinus venosa as the posterior barrier during AFL.

During CS pacing, all cases exhibited conduction through the ER

with an rS pattern.

Different ablation strategy in the aged during AFL

RA substrate properties associated with age in patients with typical AFL

Huang JL et al. Heart Rhythm. 2008;5(8):1144-51

• OBJECTIVE: to characterize the difference in the right

atrial (RA) substrate related to aging using noncontact

mapping of the right atrium.

Fig 2

CT

A young patients with AFL

Fig 3

SV

CT

An old patients with AFL

Methods

• A total of 54 patients (23 young [<60 years] and 31 old [ 60 ≧

years]) with typical AFL who underwent 3-D noncontact mapping

of typical AFL were enrolled in the study.

• The atrial substrate was characterized according to

(1) regional wavefront activation mapping,

(2) regional conduction velocity

(3) regional voltage distribution by dynamic substrate mapping.

RESULTSDuring activation mapping of the crista terminalis, two activation

patterns were observed:

(1) around the upper end of the crista terminalis (67%)

(2) through a gap in the crista terminalis.

(3)The presence of a crista terminalis gap was associated

with a high incidence of induced atypical AFL/atrial

fibrillation (P <.001). More cases with a low-voltage zone (<or=30% peak negative

voltage) extending to the medial side of the cavotricuspid isthmus occurred in the old group than in the young group (55% vs 17%, P = .012).

P=0.003

P=0.04

The conduction velocities of the medial CTI were slower in the old group than in the young group.

Locations of the Slowest Conduction during AFL

6%

40%

33%

21%

13%

8%

71%

8%

< 60 y/o > 60 y/o

P < 0.01

In regional activation mapping of the AFL, the location of the slowest conduction shifted from the lateral cavotricuspid isthmus (71%) in the young group to the medial cavotricuspid isthmus (40%) in the old group.

A: 43 yr malePNV= -4.2 mV

B: 79 yr malePNV= -3.9 mV

SVC

IVC

SVC

IVC

CT

SVC

IVC

SVC

IVC

CT

Conclusions

• Three-dimensional mapping showed the different patterns of

activation in the Eustachian during AFL.

• Analysis of atrial substrate could show the information of

protected isthmus during atypical atrial flutter, which could

provide important strategy for ablation.

• Different atrial substrate in the young and old patients with

AFL and strategy of ablation should be adjusted in the

clinical practice for these two groups.

What else? Besides activation mapping!!

Substrate analysis!!

Atypical AFLAtypical AFL

Upper loop reentryUpper loop reentry

Lower loop reentryLower loop reentry

Scar (low voltage zone) reentryScar (low voltage zone) reentry

Double loop (Figure-8) reentryDouble loop (Figure-8) reentry

Upper Loop Reentry

Where is the target ?

IV1

6789

1011

˙

9

LVZ

LVZAblation line

Figure 3-B

Atypical AFL (Upper loop reentry)

Septum

LVZ

CT

Voltage map Virtual electrograms

ActivationIsochronal map

LVZ

LVZ

IVC

IVC

SVC

1 cm

B. Ablation siteA. Voltage map before ablation

C. Voltage map after ablation

Virtual 10 Virtual 10

11

12

11

12

10

1112

1 cm

0--5%5-10%10-15%15-20%20-25%25-30%30-35%35-40%40-45%45-50%50-55%55-60%60-65%65-70%70-75%75-80%80-85%85-90%90-100%

Ratio to themaximum PNVVoltage maps before & after ablation

A: SR

C: LAL pacing

B: CSO pacing

D: Atypical flutter

% of global maximum PNV

Septum

Lateral wallCT

IVC

SVC

1

23

1

23

Voltage map: Normalized to Global Maximal PNV

1.5 mV

2.1 mV

3.4 mV

1.2 mV

0.2 mV

0.8 mV

LVZ

LVZ

B C

F

LVZ LVZ

LVZ

LVZ

LVZ LVZ LVZ

LVZ

LVZ LVZ

A B C D E FVirtual 10

11

12

13

14

15

H: Virtual electrograms

A

G: Intracardiac tracing

A B C D E F

ED

LVZ

LVZ

IVC

SVC

Virtual 1

2

3

1

LVZ

Voltage mapping before ablation Voltage mapping after ablation

% of global maximum PNV

Virtual 1

2

3

12

3

IVC

32Pacing from

CSOPacing from CSO

Substrate Mapping to Detect Abnormal Atrial Endocardium with Slow Conduction in Patients with Atypical Right AFL

Huang JL et al. J Am Coll Cardiol 2006 ;48(3):492-8

• Atypical RA AFL was induced by atrial pacing in 12 patients,

• The protected isthmuses were near the crista terminalis.

• The conduction velocities within these paths were

significantly slower than outside the path (0.30±0.18 m/s vs.

1.14±0.41 m/s, respectively, p=0.004).

A: PNV voltage map

B: Isopotential activation maps

C: Unipolar Eg

1

2

3

4

5

LVZ

LVZ

Isthmus 1234

5

(1) (2) (3)

(4) (6)(5)

SVC

IVC

CT

54

3 2 1123

45

CT123

45

CT

1234

5

CT1234

5123

45

% o

f gl

obal

max

imum

PN

V

Ratio to the maximal peak negative voltage

Maximal peak negative voltage of a selected beat

Normalized Negative Unipolar Voltage

Identify the Protected Isthmus:

bordered by the low voltage zones

Isthmus

LVZ

Convergence of voltage lines

LVZ

LVZ LVZ

LVZLVZ

LVZ

LVZLVZ

LVZ

LVZ LVZ LVZ

% o

f g

lob

al m

axim

um

PN

VProtected Isthmus during RA AFL in 6 pts

Isthmus

Mean width: 1.7 ± 0.3 cm2 (1.2 cm2 to 2.3 cm2) Mean voltage at the isthmus: -0.91 ± 0.39 mV (-0.33 to -1.69 mV)

with equivalent to 43 ± 14 % of the maximal PNV (23 to 58%).Local Eg were widely fragmented, indicating slow conductionThe conduction velocities within paths were significantly slower

than outside the path (0.30±0.18 m/s vs. 1.14±0.41 m/s, p=0.004).

LVZ

LVZ

Characteristics of the protected isthmus

P = 0.01P = 0.004

PNV Coduction Velocity

Result (I)Result (I)Prediction of slow conduction of the protected isthmusPrediction of slow conduction of the protected isthmus

Fixed voltage: -0.54 mV was the best cut-off value by local Eg voltage

(sensitivity=61.5% and specificity=85.7%, CI=95%).

Ratiometric voltage: 37.6% to the maximal PNV was the best cut-off value

(sensitivity=92.3% and specificity=85.7%, CI=95%).

0 20 40 60 80 100

100-Specificity (%)

100

80

60

40

20

0

Se

ns

itiv

ity

(%

)

0.8

0.7

0.6

0.5

0.4

0.3

0.2

0.1

Inside isthmus

A: ROC Curve Analysis B: Ratiometric voltage

Ra

tio

me

tric

Vo

lta

ge

Outside isthmus

Result (II)Result (II)

Radiofrequency ablationRadiofrequency ablation Delivery of ablation energy across the path was successful

(8.8 ± 2.6 pulses), suggesting it represented the critical isthmus of the reentrant circuit.

After ablation, voltage mapping showed significant reduction of unipolar negative voltage at the protected isthmus and double potentials appeared, which indicated conduction block. The activation propagated around the upper end of CT, instead of conducted through the protected isthmus.

ConclusionsConclusions

NCM in patients with atypical RA AFL consistently demonstrated slow conduction within LVZ’s in and around the CT.

Characterization of the RA substrate in terms of unipolar PNV is an effective predictor of the slow conduction path within the critical isthmus of the reentrant circuit.

A ratiometric threshold, normalized by the maximum PNV, improves the diagnostic accuracy over a fixed amplitude threshold.

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