Atrial Tachycardia With Atrial Activation Duration Exceeding the Tachycardia Cycle Length

JACC: CLINICAL ELECTROPHYSIOLOGY

VOL.

-, NO. -, 2019

ª 2019 BY THE AMERICAN COLLEGE OF CARDIOLOGY FOUNDATION PUBLISHED BY ELSEVIER

Atrial Tachycardia With Atrial Activation Duration Exceeding the Tachycardia Cycle Length Mechanisms and Prevalence Philippe Maury, MD,a,b,* Masateru Takigawa, MD,c,d,* Stefano Capellino, BE,e Anne Rollin, MD,a Jean Rodolphe Roux, BE,e Pierre Mondoly, MD,a Franck Mandel, MD,a Benjamin Monteil, MD,a Arnaud Denis, MD,c,d Frederic Sacher, MD,c,d Meleze Hocini, MD,c,d Michel Haïssaguerre, MD,c,d Nicolas Derval, MD,c,d Pierre Jaïs, MDc,d

ABSTRACT OBJECTIVES This study sought to identify atrial tachycardia (AT) demonstrating atrial activation duration (AAD) lasting longer than the length of the tachycardia cycle (TCL); to assess AT prevalence; and to evaluate the mechanisms and characteristics associated with these AT episodes by using the Rhythmia system (Boston Scientific, Marlborough, Massachusetts). BACKGROUND Ultra-high-density mapping allows very accurate characterization of mechanisms involved in AT. Some complex patterns may involve AAD which is longer than the tachycardia cycle length (TCL) which makes maps difficult to interpret. Prevalence and characteristics of such ATs are unknown. METHODS A cohort of 100 consecutive patients undergoing ablation of 125 right (n ¼ 21) or left (n ¼ 104) ATs using ultra-high-density mapping were retrospectively included. Offline calculation of right or left AAD was compared to TCL. RESULTS Mean TCL was 293  65 ms, and mean AAD was 291  74 ms (p ¼ NS). AT mechanisms were macro-re-entry in 74 cases (59%), localized re-entry in 27 cases (22%), and focal AT in 21 cases (17%) (types were mixed in 3 cases). Fifteen ATs (12%) had AADs that were longer than the TCL (71  45 ms longer, from 10 to 150 ms). TCL was equal to the AAD in 97 ATs (78%), whereas 13 ATs (10%) had AAD shorter than the TCL (focal AT in each case). There were no differences between right and left atria for prevalence of ATs with AADs that were longer than the TCLs. There were significant differences in AT mechanisms according to the AAD-to-TCL ratio (p < 0.0001), with localized re-entry showing more often that AAD was longer than the TCL compared to that in focal AT and macro-re-entry. CONCLUSIONS ATs with AAD lasting longer than the TCL were present in approximately 10% of the ATs referred for ablation, mostly in ATs caused by localized re-entry. Ultra-high-density mapping allows detection of these complex patterns of activation. (J Am Coll Cardiol EP 2019;-:-–-) © 2019 by the American College of Cardiology Foundation.

D

etailed knowledge of the precise mecha-

ablation or surgery. Ultra-high-density mapping may

nisms underlying atrial tachycardia (AT) re-

achieve very accurate characterization of circuits/

mains challenging, especially in patients

mechanisms in AT (1). For example, bi-atrial AT and

with complex atrial scarring from previous atrial

dual- or triple-loop re-entry have been described using

From the aDepartment of Cardiology, University Hospital Rangueil, Toulouse, France; bUnité Inserm U 1048, Toulouse, France; c

Department of Cardiology, University Hospital Haut-Lévèque, Pessac, France; dLIRYC Institute/INSERM 1045, Bordeaux Uni-

versity Hospital, Bordeaux, France; and eBoston Scientific, Voisin Le Bretonneux, France. *Drs. Maury and Takigawa contributed equally to this work and are joint first authors. Drs. Capellino and Roux are employees of Boston Scientific. All other authors have reported that they have no relationships relevant to the contents of this paper to disclose. All authors attest they are in compliance with human studies committees and animal welfare regulations of the authors’ institutions and Food and Drug Administration guidelines, including patient consent where appropriate. For more information, visit the JACC: Clinical Electrophysiology author instructions page. Manuscript received November 5, 2018; revised manuscript received April 23, 2019, accepted April 25, 2019.

ISSN 2405-500X/$36.00

https://doi.org/10.1016/j.jacep.2019.04.015

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AT With Atrial Activation Exceeds Tachycardia Cycle Length

ABBREVIATIONS

high-density mapping with the Rhythmia 3D

macro-re-entry (re-entry circuit including either the

AND ACRONYMS

electroanatomical system (Boston Scientific,

cavotricuspid isthmus, left atrial roof, and/or the

Marlborough, Massachusetts) (2,3). Due to

mitral isthmus); or a combination of these. AT

the high resolution and high density of the ac-

mechanisms were assessed mainly by analyzing

quired data and smart annotation of complex

activation maps and by termination of AT during

electrograms (EGM) this 3-dimensional (3D)

ablation. Although entrainment mapping may char-

mapping system may reveal unexpected com-

acterize focal or re-entrant mechanisms as well, this

plex mechanisms and re-entry characteristics

technique was marginally used here because of the

(4) that are possibly misdiagnosed by other

risk of AT modification or interruption. Based on the

3D-electroanatomical systems (5).

authors’ previous experience, ultra-high-definition

AAD = atrial activation duration

AF = atrial fibrillation AT = atrial tachycardia CTI = cavotricuspid isthmus LA = left atrium LAA = left appendage RA = right atrium

Another very complex and unexpected AT

RIPV = right inferior pulmonary

feature would be met if the duration of atrial

vein

activation (AAD) exceeds the tachycardia cy-

TCL = tachycardia cycle length

mapping alone may depict AT mechanisms with enough precision using the Rhythmia system (8–14). Right

and/or

left

AAD

were

calculated

and

cle length (TCL) (6). Even if this is apparently

compared to the AT cycle length. TCL was defined as

paradoxical, this may be theoretically possible in case

the duration between consecutive stable local acti-

of major conduction disturbances in some parts of the

vation at the reference catheter. AAD was determined

atrium, for example, in extremely scarred atrial tis-

by analyzing propagation maps while programming

sues, either from disease or extensive ablation or

the width of the activation wave front (see brown

surgery. This complex pattern of activation, some-

wave) to 10 to 20 ms. AAD was defined as the time

times suspected in confusing and chaotic, difficult-to-

required to activate all parts of the atrium by a single

understand maps (6), remains very difficult to prove. Standard 3D mapping systems are not able to clearly

or multiple simultaneous wavefronts. F o c a l a t r i a l t a c h y c a r d i a . For focal AT, AAD was

depict activation waves outside the “window of in-

evaluated by the duration between the onset of focal

terest” which is not expected to exceed the TCL.

emergence, the earliest atrial activation, and the end

Because the Rhythmia system does not rely on simply

of the depolarizing wave coming from this focal

a “window of interest” but rather on showing propa-

discharge after the entire atrium has been activated.

gation of any depolarizing wave whatever the timing,

R e - e n t r y . For re-entry, an arbitrary reference point

the present authors postulated that Rhythmia could

was chosen, and the wave front boundary (or

deal with this issue if it really exists.

boundaries) was tracked over the entire atrium until

This study aimed to identify AT demonstrating an

it returned to this reference point. If the entire atrium

AAD longer than the TCL, to assess their prevalence,

was depolarized within 5 ms of the returning wave,

and to evaluate the mechanisms and characteristics

AAD and TCL were considered equal. If there was

associated with these ATs by using the Rhythmia

continued activation of some part of the atrium not

system.

previously depolarized by the tracked wavefront(s) for a period 5 ms greater than the TCL, AAD was

METHODS

determined to be greater than the TCL.

Consecutive patients undergoing percutaneous radi-

calculation. Examples, methods of calculation, and

ofrequency (RF) ablation of AT using high-density

explanations of ATs with AAD longer than the TCL are

Pulmonary vein activation was not included in the

mapping with the Rhythmia system were retrospec-

provided in Figures 1 to 3 (focal AT) and Figures 4, 5

tively included at both our Toulouse and Bordeaux

and Central Illustration (re-entry). Online Videos 1

centers from the end of 2014 to the beginning of 2017.

and 2 illustrate these examples.

Biatrial ATs were excluded, together with ATs dis-

Signed informed consent was obtained from all

playing irregular TCL (beat-to-beat variations >10%

patients, and the study was performed in accordance

TCL or >20 ms) (7) or showing a dissociated part of

with ethical standards and declared to the Commis-

the atrium (i.e., no 1:1 relation to the mapped AT).

sion Nationale de l’Informatique et des Libertés, ac-

Antiarrhythmic drugs were withheld at least 5 half-

cording to French law.

lives before the procedure with the exception of

STATISTICS. Categorical variables are numbers and

amiodarone.

proportions and were compared using the chi-square

Mechanisms of AT were defined as focal (concen-

test or Fisher exact test as appropriate. Continuous

tric activation of the whole atrium from one localized

variables were expressed as mean  SD and compared

area without returning wave front to this area, i.e., no

using unpaired t-test. Arrhythmia-free Kaplan-Meier

“early-meets-late”); localized re-entry (recording of a

survival curves were built and compared using the

full re-entry circuit not related to macro-re-entry);

log-rank test.

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F I G U R E 1 Schematic of a Focal AT With AAD Longer Than the TCL

Activation breaks before the full activation from the previous one was terminated. AAD ¼ atrial activation duration; AT ¼ atrial tachycardia; TCL ¼ tachycardia cycle length.

Analysis

and

calculations

were

performed

RESULTS

using StatView version 5.0 software (Abacus Concepts, Inc., Berkeley, California). A p value < 0.05

A cohort of 100 consecutive patients undergoing

was considered statistically significant for each

ablation of 125 ATs using ultra-high-density mapping

analysis.

with the Rhythmia system were retrospectively

F I G U R E 2 Example of a Focal Right AT With AAD Longer Than the TCL

Lateral (left) and septal (right) views of the right atrium in different parts of the cycle length. 1. AT arises from a lateral focus while there is still final depolarization on the septal side (arrows and brown waves). 2. Activation centrifugally invades the lateral wall while there is no more activation on the septal side. 3. Activation waves leave the lateral wall and begin to meet on the septal side. 4. Lateral wall is silent during the final activation of the septal side, which is not fully terminated before a new focal activation arises (see part 1). IVC ¼ inferior vena cava; SVC ¼ superior vena cava; TS ¼ tricuspid annulus; other abbreviations as in Figure 1.

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F I G U R E 3 Succession of Electrograms (see Figure 2)

The concentric activation of the whole right atrium from a focal source at the lateral part (yellow arrow) is longer than the TCL. The AAD is calculated from site 1 (onset of focal activation) to site 6 (termination of activation) (dashed red line) and then compared to the TCL. Note that this point is slightly delayed compared to the new activation occurring at site 1 (See Online Video 1). Abbreviations as Figures 1 and 2.

included (21 right and 104 left AT; 1 to 4 AT per

time for each AT was 925  445 s. A mean 13,550 

patient; mean: 1.25). Clinical characteristics of the

6,316 points were recorded for each AT, correspond-

patient population are shown in Table 1. Ninety

ing to 1,422  667 beats. RF ablation was performed

percent of the patients had already undergone atrial

using standard irrigated catheters (n ¼ 108 Thermo-

ablation, and almost one-half had a structural heart

cool, Biosense Webster, Irvine, California; n ¼ 3,

disease.

IntellaNav, Boston Scientific, Marlborough, Massa-

Standard programmed atrial stimulation or 250 ms

chusetts; or contact force irrigated catheters (n ¼ 14

burst pacing were performed when the patient was in

Tacticath, Abbott Laboratories, Lake Bluff, Illinois).

sinus rhythm at the onset of the procedure. Isopro-

All but 8 ATs were successfully terminated during RF

terenol was used when tachycardia was not inducible

delivery (mean time to AT termination: 386  852 s).

at baseline.

There were no immediate complications except for

Mean procedural duration was 244  79 min, and mean fluoroscopy duration was 55  33 min. Mapping

cerebral hemorrhage in 1 patient a few hours after the procedure.

F I G U R E 4 Schematic Shows a Re-Entry Circuit With AAD Longer Than the TCL

Activation of a bystander channel issued from the circuit leads to a whole atrial activation which exceeds the TCL.

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F I G U R E 5 Example of an Atrial Re-entry With AAD Longer than the TCL

Superior (left) and right lateral (right) views of the left atrium in different parts of the cycle length. Black dots represent areas of block. 1. Reference point of the reentry: activation goes through a lateral gap along the roof line, while a remote depolarization wave invades a bystander dead end pathway below the right inferior pulmonary vein (arrows and brown or purple waves). 2. Activation turns anteriorly and rightward to the roof line of block, dividing in the main rotating wave, and a second bystander wave goes anteriorly, while there is no more activation on the septal side. 3. Activation goes posteriorly through a medial gap along the roof line, while the anterior bystander wave is descending toward the septum. 4. The main rotating wave proceeds laterally and leftward before entering the lateral gap (reference point), while the septal bystander activation proceeds into the dead-end pathway. This activation will terminate after step 1 of the next cycle, thus AAD is superior to TCL. LAA ¼ left atrial appendage; LPV ¼ left pulmonary veins; RIPV ¼ right inferior pulmonary vein; RSPV ¼ right superior pulmonary vein; other abbreviations as in Figure 1.

Mean TCL was 293  65 ms, and mean AAD was

For ATs with a single mechanism (n ¼ 122), there

291  74 ms (p ¼ NS). AT mechanisms were macro-re-

were significant differences in AT mechanisms ac-

entry in 74 (59%), localized re-entry in 27 (22%), and

cording to the AAD-to-TCL ratio (p < 0.0001)

focal AT in 21 (17%) (types were mixed in 3 cases).

(Table 2). Localized re-entry more often consisted of

There were 5 focal, 13 macro-, and 3 localized re-entry

AADs that were longer than the TCL compared to

for right ATs vs. 16, 61, and 24 for left ATs respectively

focal ATs and macro-re-entry. The 3 ATs with mixed

(p ¼ NS). TCL was equal to AAD in 97 ATs (78%).

mechanisms showed AADs were equal to the TCLs.

Thirteen ATs (10%) had AAD shorter than the TCL

The differences remained highly significant when

(106  82 ms shorter, from 10 to 317 ms) representing

only ATs with AAD equal to or superior to TCL were

20% to 97% of TCL (mean: 67  21), and all of them

compared (p < 0.0001) or when ATs with AAD longer

were focal AT. Fifteen ATs (12%) had AADs longer

than

than the TCL (71  45 ms longer, from 10 to 150 ms)

(p ¼ 0.0015).

the

TCL

were

compared

to

other

ATs

(4 focal AT, 3 macro and 8 localized re-entry) due to

Details of the 15 ATs with AAD longer than the TCL

delayed activation (when wave extinction occurs at

can be found in Table 3 as well as sites of latest atrial

some distant parts of the atrium after a new activa-

activation, which were usually found as dead-end

tion has begun in the circuit of at the focus).

pathways at the opposite part of the atrium.

ATs with AADs shorter than, equal to, or longer

Compared to other ATs, ATs with AAD were longer

than the TCLs were found either in the right or left

than the TCL showed longer AAD (341  71 vs.

atrium without significant differences (19%, 71%, and

284  72 ms, respectively; p ¼ 0.004) but nonsignif-

10% for right ATs versus 9%, 79%, and 12% for left

icantly shorter TCLs (270  64 vs. 296  65 ms,

ATs; p ¼ NS).

respectively; p ¼ 0.15).

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C E NT R AL IL L U STR AT IO N Succession of Electrograms (see Figure 5)

Maury, P. et al. J Am Coll Cardiol EP. 2019;-(-):-–-.

Full cycle length activation along a localized circuit is shown from site 1 (reference point) to site 6 (yellow arrows). Sites 7 and 8 were lately activated from an anterior site, turning around the previous ablation lines, and then invading a gap before ascending into the PV antrum (red arrow). Black dots represent areas of block. AAD is calculated from site 1 (onset of activation) to site 8 (termination of activation) and then compared to the TCL. Note that this site is delayed compared to the next activation at site 1 (reference point) (dashed red line) (See Online Video 2). Abbreviations as in Figure 5.

One patient had 2 ATs with AADs longer than TCLs,

to follow-up). There were no differences in the

whereas 6 patients had ATs with AADs longer than

recurrence rate of any atrial arrhythmia in patients

TCLs, together with other ATs. Apart from 1 case, ATs

with or without ATs with AADs longer than the TCLs

with AADs longer than TCLs were observed exclu-

(6 of 12 vs. 38 of 75, respectively; p ¼ ns) nor in re-

sively in patients with structural heart disease and/or

currences of ATs (6 of 12 vs. 28 of 75, respectively) or

in cases of previous ablation. However, patients with

atrial fibrillation (1 of 12 vs. 7 of 75, respectively;

at least 1 AT with AADs longer than the TCLs did not

p ¼ NS). Kaplan-Meier estimates did not show any

differ according to sex, presence of heart failure, age,

differences for AT or for atrial fibrillation recurrence

hypertension, diabetes, previous surgery or previous

over the follow-up between patients with and

percutaneous ablation, presence of congenital or

without ATs with AADs longer than the TCL (p ¼ 0.9

structural heart disease, use of class 1 or class 3 drugs,

for each comparison).

left ventricular ejection fraction or left atrium volume compared to patients without AT with AADs longer

DISCUSSION

than the TCLs. There were no differences in procedure and fluoroscopy duration, mapping time, number

Previous extensive ablation and/or atrial scarring or

of recorded electrograms/beats, immediate success,

fibrosis may significantly prolong right or left intra-

and mean time to AT termination between ATs with

atrial conduction times and thus may alter paths of

AADs longer than the TCLs and other ATs.

activations outside re-entry circuits or centrifugal

Patients were discharged without (n ¼ 72) or with (n ¼ 38) antiarrhythmic drugs (NA in 5). Over a mean

ATs, making activation maps confusing and diagnosis more difficult (9).

follow-up of 12  6 months, ATs recurred in 44 pa-

This study found that ATs demonstrating AADs

tients and atrial fibrillation in 8 (13 patients were lost

longer than TCLs were not exceptional, representing

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T A B L E 1 Patient Clinical Characteristics

T A B L E 3 Details of the 15 AT Patients With AAD Longer Than the TCL*

Men

63 (63)

Patient

TCL

AAD

Localization

Mechanism

61  13 (19-81)

1

275

285

RA lateral wall

Focal

Septal RA

LVEF

54%  12% (20%-78%)

2

440

477

LA anterior

Loc re-entry

LA post wall and right post septum

Antiarrhythmic drugs

Class 1 15 Amiodarone 40 Sotalol 12 None 33

3

290

352

RA CTI

Macro

SVC

4

240

305

LA roof

Focal

Anterior LA

5

240

390

LA post wall

Loc re-entry

Anterior LA

6

255

265

LA anterior

Loc re-entry

LA post wall

7

240

280

LA ridge

Focal

LA post wall

8

265

375

LA roof

Macro

Septal LA

9

260

410

LA post wall

Loc re-entry

Septal and anterior LA

Age, yrs (range)

Previous cardiac surgery

14 (14)

Previous ablation

AF 72 AT 16 Surgical 7 None 13

Site of Latest Activation

8 (8)

10

235

282

LA mitral

Macro

Septal LA

RA volume

123  44 ml (55-221)

11

240

275

LA septum

Loc re-entry

Lateral LA

LA volume

158  81 ml (37-480)

12

381

446

LA LAA

Loc re-entry

Inferior LA

40 (40)

13

290

400

LA RIPV

Loc reentry

LA post wall

9 (9)

14

204

314

LA post wall

Loc re-entry

Lateral LA

Congestive heart failure

25 (25)

15

200

260

LA septum

Focal

Lateral LA

Structural heart disease

47 (47)

Congenital heart disease

Hypertension Diabetes

Sites of latest atrial activation were usually found as dead-end pathways at the opposite part of the atrium, sometimes due to gaps in previous lines around the pulmonary vein antrum.

Values are n (%) or mean  SD.

AAD ¼ atrial activation duration; LA ¼ left atrium/atrial; LAA ¼ left appendage; Loc ¼ localized; Macro ¼ macro reentry; RA ¼ right atrium/atrial; RIPV ¼ right inferior pulmonary vein; SVC ¼ superior vena cava; TCL ¼ tachycardia cycle length.

AF ¼ atrial fibrillation; AT ¼ atrial tachycardia; LA ¼ left atrium/atrial; LVEF ¼ left ventricle ejection fraction; RA ¼ right atrium/atrial.

approximately 1 of 10 ATs referred for ablation at our

thousands of points/electrograms allows to better

centers. These ATs are more frequently observed in

define the different activation waves, irrespective to

cases of localized re-entry and may be seen equally in

their relative timing in the “window of interest.”

the right and left atrium, without any other signifi-

Thus, visualization and recognition of complex pat-

cant clinical correlation.

terns of activation is easier and helps understanding

Ultra-high-density mapping may facilitate recog-

what is going on during the whole atrial activation.

nition and understanding of these complex patterns

Apart from one previous case report (6), to the best

of activation, which are possibly more difficult to

of the author’s knowledge, only one previous study

understand using more conventional 3D mapping

investigated ATs associated with atrial conduction

systems. Using these systems, EGMs at distant sites

disturbances (9). In this study (9) including thirteen

not belonging to the current activation wave will be

focal ATs with confusing activation mimicking macro-

tagged as they appear in the annotation window,

re-entry or with fully chaotic activation and disorderly

causing some confusion. The “window of interest” is

color arrangement, AADs approached and sometimes

usually chosen close to the cycle length duration in

surpassed the duration of the “window of interest”

these systems, which only represents the time be-

(max 1.3 times longer) (9). Even if the AAD was not

tween consecutive focal activations or the duration of

compared to the TCL in this study, the “window of

a complete circuit re-entry. This might be different

interest” was set to only 10 to 20 ms less than the TCL.

from the complete atrial activation time, which may

In the present study, ATs with AADs longer than

include delayed areas and/or bystander or dead-end

the TCLs were in fact ATs where distant areas in the

pathways.

same chamber were depolarized late after focal acti-

Ultra-high-density

mapping

recording

vation or far from the re-entrant wave, and whose T A B L E 2 Mechanisms of ATs According to the AAD/TCL Ratio

conduction properties/size were allowed to perpetuate activation once the following cycle had begun.

Focal AT (n ¼ 21)

Macro Re-entry (n ¼ 74)

Localized Re-entry (n ¼ 27)

Atrial activation duration ¼ tachycardia cycle (n ¼ 94)

4

71

19

Atrial activation duration > tachycardia cycle (n ¼ 15)

4

3

8

Atrial activation duration < tachycardia cycle (n ¼ 13)

13

0

0

Atrial Activation Duration/ Tachycardia Cycle Ratio

AT ¼ atrial tachycardia.

Using other 3D mapping systems, uninterpretable mapping was observed in approximately 10% of ATs occurring after previous atrial fibrillation or AT ablation, which were finally related to focal AT in every case (9). The use of entrainment and post-pacing intervals was the only way to fix this issue in studies using more conventional 3D mapping systems (6,9). The AAD-to-TCL ratio is used in the definition of mechanisms of ATs, with focal ATs usually displaying

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AAD <50% of the TCL (9), meaning that there is no

unlike those in other studies (9). It remains to be

atrial depolarization during more than one-half of the

determined whether long AADs result from high-rate

TCL and with AAD being equal to TCL in ATs based on

activation and decremental conduction and/or area of

re-entry. The AAD-to-TCL ratio was 16  6% (7:26) in

functional blocks or from true baseline slow conduc-

the right focal ATs (10). In the present study, when

tion due to fixed areas of block or both.

ATs with AADs longer than the TCLs were excluded,

Biatrial mapping during AT was not performed in

focal ATs had mean 74  23% AAD-to-TCL ratio (from

most cases. Therefore, the study may have under-

20% to 100%).

estimated ATs with biatrial AAD greater than TCL

However, if focal ATs are usually expected to

greater than TCLs. However, a bystander atrium

manifest centrifugal activation patterns with atrial

usually has a short activation time because it is usu-

activation times accounting for <50% of TCL (9), this

ally less diseased. Additional studies would be

depends on both the TCL and the AAD. The AAD as

needed to systematically investigate that issue.

measured during sinus rhythm or coronary sinus

Electrocardiography (ECG) characteristics of ATs

pacing has been reported to vary significantly from 30

with AADs longer than the TCLs were not evaluated

to 100 ms for the right and from 80 to 110 ms for the left

here. Interatrial conduction disturbances are known

atrium, according to the presence of previous surgery,

to enlarge P waves and to lead to specific P wave ECG

atrial fibrillation, or type of AT (9–12), which may have

patterns (13), but further studies will be required to

an impact on the AAD. Because ATs with a TCL less

determine if intra-atrial conduction delays possibly

than these values are not met in clinical practice, the

present in ATs with AADs longer than the TCLs may

usual definition of focal AT having AADs less than the

be detectable on 12-lead ECG.

TCLs remains true for most cases, especially in healthy

Entrainment at dead-end pathways, although

atria because of fast and nondisorganized atrial con-

potentially useful in sorting such AT mechanisms,

duction in the whole atrium without bystander or a

was not performed in this study (see Methods). It

dead-end pathway. In very diseased atria, however,

could have been important to perform as the authors

ATs may have AADs longer than the TCLs, especially

acknowledge that some maps remain difficult to un-

when they are rapid. In the present study, however,

derstand even with the Rhythmia system. Entrain-

ATs with AADs longer than the TCLs did not present

ment

with significantly shorter TCLs but were almost

assessing the role of some atrial structures. This is

exclusively observed in patients with structural heart

especially true for dead-end pathways and also

disease and/or in cases of previous ablation.

sometimes the only way to differentiate between

AADs longer than TCLs do not mean, per se, that AT will degenerate into atrial fibrillation because of

mapping

remains

an

important

tool

for

focal AT with bystander loop and true loop with apparent block at a local isthmus.

new activation waves colliding on partially refractory

Finally, the recurrence rate was high due to the

tissues from the previous extinguishing wave. Suc-

population studied (redo cases) but was realistic in

cessive waves simply follow altered paths of activa-

this challenging patient population. In similar pa-

tion with local conduction disturbances without

tients with similar follow-up durations, a recent se-

colliding themselves, although complete activation of

ries of AT ablations found a 42% recurrence rate with

some parts of the chamber is not terminated when a

high-density mapping (1), whereas Anter et al. (14)

new wave is arising. In the present study, patients

found a 25% recurrence rate for much shorter

with ATs showing AADs longer than the TCLs did not

follow-up periods.

present with more recurrences of atrial fibrillation. On the other hand, such scarred atria can hardly

CONCLUSIONS

generate high rates of activation required for atrial fibrillation.

Atrial tachycardia with AADs longer than the TCLs are not exceptional and can be present for every AT

STUDY LIMITATIONS. There was possibly some se-

mechanism: focal, macro, or localized re-entry. This

lection bias in the studied population, as ATs mapped

should be recognized as it may account for uninter-

and ablated at both of the authors’ centers with the

pretable maps using standard 3D systems.

Rhythmia system were redo and/or challenging cases with very diseased atria. Accordingly, the true prev-

ADDRESS

alence of ATs with AADs longer than TCLs in unse-

Maury,

lected patients may possibly be lower.

Hospital Rangueil, 1 Avenue du Professeur Jean

Scar surface or atrial activation time during sinus rhythm or atrial pacing were not evaluated here,

FOR

CORRESPONDENCE:

Department

of

Cardiology,

Dr. Philippe University

Poulhès, 31059 Toulouse Cedex 09, France. E-mail: [email protected].

JACC: CLINICAL ELECTROPHYSIOLOGY VOL.

-, NO. -, 2019

Maury et al.

- 2019:-–-

AT With Atrial Activation Exceeds Tachycardia Cycle Length

PERSPECTIVES COMPETENCY IN MEDICAL KNOWLEDGE: Using

TRANSLATIONAL OUTLOOK: Further refinements are

high-density mapping, expectation and recognition of

needed in mapping AT for better determination of the

AT having a duration of atrial activation longer than the

potential mismatch between tachycardia cycle length and

tachycardia cycle length is useful, especially when

duration of atrial activation.

mapping AT in patients with diseased atria and may avoid misunderstanding of the mechanism.

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KEY WORDS ablation, activation duration, atrial tachycardia, bystander, focal tachycardia, re-entry, tachycardia cycle length

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A PPE NDI X For supplemental videos, please see the online version of this paper.

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