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Clinical Electrophysiology

Editor-in-Chief

Dr. David J. Wilber.

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Utility of a Novel RapidHigh-Resolution Mapping System in theCatheter Ablation of Arrhythmias
An Initial Human Experience of Mapping the Atriaand the Left Ventricle
Lilian Mantziari, MD, Charles Butcher, MBBS, Andrianos Kontogeorgis, MBBCH, Sandeep Panikker, MBBS,Karine Roy, MD, Vias Markides, MD, Tom Wong, MD

ABSTRACT

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OBJECTIVES This study sought to assess the clinical efficacy, safety, and clinical utility of a novel electroanatomical

mapping system.

BACKGROUND A new mapping system capable of rapidly acquiring detailed maps based on automatic annotation of

thousands of points was recently released for clinical use. This is the first description of its utility in humans.

METHODS The first consecutive 20 cases (7 atrial tachycardia, 8 atrial fibrillation, 3 ventricular tachycardia, and 2 ven-

tricular ectopic beat ablations) were analyzed. The system uses a bidirectional deflectable basket catheter with 64 closely

spacedmini-electrodes. It automatically accepts and annotates electrograms when a number of predefined criteria aremet.

RESULTS Thirty right atrial maps were acquired in 11 (4 to 15) min, consisting of 7,220 (3,467 to 10,947) points, 22 left

atrial maps in 11 (6 to 19) min, consisting of 7,818 (4,379 to 12,262) points and 10 left ventricular maps in 37 (14 to 43)

min, consisting of 8,709 (2,605 to 15,514) points. The mini-basket catheter could reach all areas of interest without

deflectable sheaths. No embolic events, bleeding complications, or endocardial structure damage were observed.

Correction of the automatic annotation was performed in 0.02% of points in 4 of 62 maps. The system revealed re-entry

circuits of atrial tachyarrhythmias, identified gaps on linear lesions, and identified and correctly annotated the clinical

ventricular ectopic beats and channels of slow conduction within ventricular scar.

CONCLUSIONS The novel automatic mapping system was rapid, safe, and efficacious in mapping a variety of cardiac

arrhythmias in humans. Further clinical research is needed to optimize its use in the ablation of complex arrhythmias.

(J Am Coll Cardiol EP 2015;1:411–20) © 2015 by the American College of Cardiology Foundation.

W idely available 3-dimensional electro-anatomical mapping systems use point-by-point acquisition of electrograms from a

roving catheter with or without multielectrode mappingcapability and usually require extensive manual re-annotation (1,2). A novelmapping system (Rhythmia, Bos-ton Scientific, Washington, DC) has recently become

m the Heart Rhythm Centre, NIHR Cardiovascular Biomedical Research Un

Royal Brompton and Harefield NHS Foundation Trust, Imperial College, L

the NIHR Cardiovascular Biomedical Research Unit of Royal Brompton

llege London. This report is independent research by the National Insti

nding Scheme. The views expressed in this publication are those of the

tional Institute for Health Research or the Department of Health. Dr. But

d research grant. Dr. Panikker is supported by a Boston Scientific research

relationships relevant to the contents of this paper to disclose.

nuscript received March 13, 2015; revised manuscript received May 11, 20

clinically available. This system is paired to a mini-basketarray catheter with 64 mini-electrodes (IntellaMap Orion,Boston Scientific) and is capableof acquiringandautomat-ically annotating thousands of points. This system hasbeen shown to rapidly obtain high-resolution maps incanine and swine models, with no need for additionalmanual annotation (3,4); however, to our knowledge, to

it, Institute of Cardiovascular Medicine and Science,

ondon, United Kingdom. This project was supported

and Harefield NHS Foundation Trust and Imperial

tute for Health Research Biomedical Research Unit

author(s) and not necessarily those of the NHS, the

cher is supported by a Boston Scientific investigator

grant. All other authors have reported that they have

15, accepted June 17, 2015.

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ABBR EV I A T I ON S

AND ACRONYMS

AF = atrial fibrillation

AT = atrial tachycardia

CL = cycle length

CS = coronary sinus

LA = left atrium

LV = left ventricle

RA = right atrium

RV = right ventricle

VE = ventricular ectopic

VT = ventricular tachycardia

Mantziari et al. J A C C : C L I N I C A L E L E C T R O P H Y S I O L O G Y V O L . 1 , N O . 5 , 2 0 1 5

Clinical Utility of Rapid High-Resolution Mapping O C T O B E R 2 0 1 5 : 4 1 1 – 2 0

412

date there is no report of the utility of this systemin humans. This paper describes the initialexperience using the Rhythmia system and themini-basket catheter, focusing on the safety,feasibility, and efficacy in mapping the atria andleft ventricle (LV) in humans.

METHODS

PATIENTS. We studied the first 20 consecu-tive electrophysiological procedures, usingthe Rhythmia mapping system at our insti-tution during the first 3 months the systemand catheter were clinically available. A

detailed description of the cases is shown in Table 1.All patients were adults (39 to 85 years of age), 7 pa-tients had structurally normal hearts, 9 patients hadhad heart failure, and 4 had adult congenital heartdisease. Fourteen patients were admitted electivelyfor procedures, and 6 patients required urgent abla-tion. Written informed consent was obtained in allcases according to standard practice. Patient andprocedural data were prospectively collected.

PROCEDURES. All procedures were performed by 2experienced operators. Atrial fibrillation (AF), atrialtachycardia (AT), and ventricular tachycardia (VT)ablations were performed on patients under generalanesthesia and transesophageal echocardiographywas performed to exclude evidence of thrombus and toguide the transseptal puncture. Two cases of ventric-ular ectopy (VE) ablation were performed with thepatient under sedation to avoid suppression of theectopy. AF and AT ablations were performed onpatients receiving uninterrupted warfarin therapywith a therapeutic international normalized ratio onthe day of the procedure. If a non–vitamin K antico-agulant was used, it was discontinued 24 to 36 h beforethe procedure, according to local guidelines. Antiar-rhythmic medications were discontinued for 5 half-lives (excluding AF cases).

Mapping system and mini-basket multielectrode catheter.The Rhythmia mapping system is a 3-dimensional(3D) electroanatomical mapping platform that uses ahybrid location technology that combines impedanceand magnetic location. The magnetic field is gener-ated by a localization generator positioned under thecatheter laboratory table and is capable of locatingthe magnetically tracked catheters with an accuracyof #1 mm. The impedance location technology isused to track catheters that are not equipped with amagnetic sensor. The system then maps the imped-ance field measurements to the magnetic locationcoordinates and creates an impedance field map.

This map is used to enhance the accuracy of theimpedance location. The Orion catheter is a bidirec-tional deflectable, multielectrode, mini-basket map-ping catheter (Figure 1). Its maximum shaft diameter is8.5-F and is advanced into cardiac chambers by us-ing 9-F sheaths. The catheter can acquire points atvariable degrees of deployment from undeployed(3 mm) to fully deployed (22 mm).Map acqui s i t ion . The Orion catheter was gentlymanipulated inside the chamber of interest and auto-matically acquired points with every accepted beat.Criteria used for beat acceptance were: 1) a stable cyclelength; 2) stable timing difference between 2 referenceelectrodes; 3) respiration gating; 4) stable catheterlocation; 5) stability of catheter signal compared toadjacent points; and 6) tracking quality. Mappingduring AF was achieved by enabling only criteria c, d,and f. For mapping of VEs and VT, an additional cri-terion of correlation to a reference surface electrocar-diogram (ECG) QRS interval morphology was applied.T ime and voltage maps . The setup for the mappingwindow was automatic. The system calculated themean cycle length of the rhythm over 10 s andconsequently set 100% of cycle length equally beforeand after the timing reference electrode (usually oneof the coronary sinus [CS] electrograms, or the QRSinterval of one of the surface ECG leads for ventric-ular rhythms). The final maps showed the activationpropagation rather that the “early” and “late” points.The mapping window could be moved at any timeduring or after the completion of the map by manu-ally dragging its ends on the screen, using thepointing device (e.g., mouse), to focus on relevantparts of the cycle length, such as the diastolic partduring VT, or to exclude nonrelevant electrogramssuch as the QRS interval during AT (Online Figure 1).

For the bipolar time maps, the timing of the electrodeswas based on the time difference between the maximumamplitude of the bipolar electrogram and the first refer-ence electrode (timing reference). For electrograms withmore than 1 potential, the system selected the potentialthat best matched the timing of the surrounding electro-grams. For unipolar time maps, the timing was basedon the most negative delta voltage/delta time (dV/dT)around the timing of the maximum bipolar signal. Thebipolar and unipolar voltage maps were based on differ-ences between the maximum and minimum peaks of thesignal. Noise level and complete electrical silence wereconsidered <0.03 mV, and low voltage areas were detec-ted between 0.03mV and 0.5mV in the atria and 0.03mVand 1.5 mV in the ventricles.Geometry . The geometry of the cardiac chambers wasgradually acquired with every accepted beat based onthe location of the outermost electrodes of the basket


TABLE 1 Case Description

Case #Age(yrs) Clinical Tachycardia

CardiovascularHistory

PreviousAblations Ablation Endpoint

Duration/Fluoroscopy

(min)Number of

MapsChamberMapped Complication Follow Duration/Outcome

1 72 Typical atrial flutter,persistent

Normal heart – Bidirectional CTI conduction block 135/10.0 2 RA None 6 months/no recurrence

2 84 Paroxysmal AT Normal heart – Left ATEPS only*

111/9.0 3 RA None No ablation

3 85 Persistent AT Normal heart – Left ATEPS only*

55/4.1 1 RA None No ablation

4 48 Typical atrial flutter,paroxysmal

Normal heart – Bidirectional CTI conduction block 80/14.5 2 RA None 6 months/no recurrence

5 68 Paroxysmal AF Normal heart – PVI 177/24.1 2 LA None 5 months/No recurrence

6 39 Persistent AT ACHD(AVSD and cleft

MV repair)

þ Right ATs/AF 3 right ATs wereinduced and ablated

178/14.1 6 RA None 4 months/12 min of SVT

7 80 Persistent AF Normal heart – PVI, roof, MVI, endocardial CS,anterior wall CFAE ablation,endocardial CS, CTI

168/39.0 3 RALA

None 6 months/no recurrence

8 54 VEs (LV) ACHD (Dextrocardia,ASD surgicallyrepaired)

– Transient elimination of VEswith endocardial ablation

188/26.0 2 LV None 3 months/NSVT

9 62 Long standingpersistent AF

DCM EF 30% – PVI, roof, MVI, endocardial CS,CTI

210/10.6 2 RALA


10 46 Persistent AF DCMEF 29%

– PVI, roof, MVI, endocardial CS lineAF organized to perimitral

AT that changed to CTIdependent flutter.

Termination to SR fromCTI ablation.

Gap on MVI ablated until block

320/21.6 5 RALA


11 54 Persistent atrialflutter

ACHD (VSD,Eisenmengersyndrome)

– Bidirectional CTI conduction block 69/10.4 4 RA None 4 months/no recurrence

12 75 Persistent AF Ischemic heart diseaseEF 60%

– PVI, roof, MVI, posterior line, CTIDCCV to roof dependent

macro-reentrant ATAblation to SR

212/8.9 4 RALA


13 71 Persistent AF Normal heart – PVI, roof, MVI, CTI 177/23.7 5 RALA


14 84 Paroxysmal AT DCMEF 55%

þ persistent AF Perimitral re-entry ATMVI block

300/14.0 3 LA None 4 months/no recurrence

15 80 Persistent AF ICM-EF 40% þ Typical flutter PVI, roof, MVI, endocardial CSDCCV to SRGap on MVI-ablation until blockCTI blocked from previous

procedure

276/51.0 3 RALA

None 2 months/persistentatrial flutter

16 71 VT storm ICM-EF 20% – Ablated 2 VTs in LV.No other VT inducible

265/34.4 2 LV None 4 months/recurrence ofVT as inpatient

Continued on the next page

JACC:CLIN

ICAL

ELECTROPHYSIO

LOGY

VOL.1,

NO.5,2015

Mantziariet

al.OCTOBER

2015:4

11–20

ClinicalUtility

ofRapid

High-R

esolutionMapping

413

TABLE

1Co

ntinu

ed

Case

#Age

(yrs)

Clinical

Tach

ycardia

Card

iova

scular

Histo

ryPr

evious

Ablations

AblationEn

dpoint

Dur

ation/

Fluo

roscop

y(m

in)

Num

berof

Map

sCh

ambe

rMap

ped

Complication

Follow

Dur

ation/

Out

come

1754

VTan

dAT

ACH

D(Bicuspidao

rtic

valve,

Ross

proc

edure,

MIp

ost

surgery,

right

corona

ryartery

torig

htatria

lfistula)

–Ablated

2VTs

inLV

.Ablated

dual-loo

pre-entry

AT

(CTI

andatrio

tomyde

pend

ent)

Non

indu

cibilityof

anytach

ycardia

298/30.7

8LV RA

Smallps

eudo

aneu

rysm

ofrig

htsupe

rficial

femoral

artery

4mon

ths/no

recu

rren

ce

1885

VTstorm

ICM

EF27

%–

Poorly

toleratedVT.

Subs

tratemap

ping

andab

lation

oflate

potentials.Clinical

VTno

tindu

cible

302/61.0

1LV

Non

e2mon

ths/no

recu

rernce

1985

VEs

ICM

EF30

%–

LVOTVEs

Elim

inationof

VEs

134/22

.11

LVNon

e3mon

ths/no

recu

rren

ce

2074

Persistent

AF

ICM

EF55

%–

PVI,roof,MVI,po

steriorlin

e,Le

ftseptum

CFAEab

lation

,CTI

AT-

perim

itralre-entry

ablation

toSR

330/6

2.0

3RA LA

Non

e2mon

ths/1ep

isod

eof

AFin

blan

king

perio

d

*Not

consen

tedforleft

side

dproc

edure.

ACH

D¼

adultco

ngen

ital

heartdisease;

AF¼

atria

lfibrillation;

ASD

¼atria

lsep

tald

efect;AT¼

atria

ltachy

cardia;A

VSD

¼atrio

ventric

ular

septal

defect;C

FAE¼

complex

fraction

ated

atria

lelectrogram

s;CS

¼co

rona

rysinu

s;CT

I¼cavo

tricuspidisthmus;D

CCV¼

direct

curren

tcardiove

rsion;

DCM

¼dilatedcardiomyo

pathy;

EF¼

ejection

fraction

;EPS

¼electrop

hysiolog

ical

stud

y;ICM

¼isch

emiccardiomyo

pathy;

LA¼

leftatriu

m;L

V¼

leftve

ntric

le;L

VOT¼

leftve

ntric

ular

outfl

owtract;MI¼

myo

cardialinfarction;

MV¼

mitral

valve;

MVI¼

mitralva

lveisthmus;PV

I¼

pulm

onaryve

inisolation;

RA¼

right

atriu

m;VEs

¼ve

ntric

ular

ectopics;VSD

¼ve

ntric

ular

septal

defect;VT¼

ventric

ular

tach

ycardia.



414

catheter. For all cases, the system was programmed toselect and include in the map only electrograms up to2 to 4 mm from the surface geometry.

STATISTICAL ANALYSIS. Normality of distributionwastested with the Kolmogorov-Smirnov test. All variableswere non-normally distributed and were reported as me-dians and interquartile ranges (25th to 75th percentiles).Stata version 13 software (Stata Corp., College Station,Texas) was used for statistical analysis. Data were logtransformed to conform to a log normal distribution. Inorder to compare the time required for mapping variouscardiac chambers with the number of accepted beats pertype of chamber and number of electrograms, while ac-counting for clustering of chambers within patients, weused linearmixedmodels analysis. A p value of<0.05wasconsidered statistically significant.

RESULTS

We present data from the first 20 consecutive pro-cedures (Table 1). Seven patients with ATs, 8 patientsundergoing ablation for AF, and 5 patients with VT orVEs ablation were studied. A total of 62 high-resolution maps were acquired with the mini-basketmapping catheter (Table 2). LV maps took longer toacquire (p < 0.0001) than right atrium (RA) and leftatrium (LA) maps, but there were no significant dif-ferences in accepted beats and electrograms acquiredamong the chambers mapped.

CATHETER MANIPULATION AND REACH. The rightfemoral vein was used to advance the basket catheterinto the atria. For RA mapping, a short 9-F sheath wasused for 28 maps, and a long, fixed curve sheath wasused for 2 maps in patients with a very dilated RA. Tomap the LA, 9-F fixed-curve long sheaths (Mullins,Cook Medical Inc., Bloomington, Indiana) were usedand allowed the basket catheter to reach all areas ofinterest in all cases. The LV was mapped using boththe transaortic and the transseptal approaches in3 cases, by the transseptal approach alone in 1 case,and by the transaortic approach alone in 1 case withdextrocardia and surgically repaired atrial septaldefect. All operators who used the catheter reportedease of manipulation in the RA and LA. There were noareas that the catheter could not reach, and it couldeasily be advanced into the coronary sinus and pul-monary veins. Mapping of the left ventricle was alsofeasible in all cases. An example of a full LV map isshown in Figure 2B.

SAFETY. The mini-basket catheter was meticulouslyflushed and inserted to the cardiac chambers after anactivated clotting time of $300 s was achieved andmaintained with boluses of intravenous heparin

FIGURE 1 The Mini-Basket Catheter

The mini-basket catheter (IntellaMap Orion, Boston Scientific)

has a bidirectional deflectable shaft. The mini-basket consists of

8 splines with 8 closely spaced mini-electrodes on each spline

that can be used in various degrees of deployment, from unde-

ployed (3 mm) to fully deployed (22 mm).

J A C C : C L I N I C A L E L E C T R O P H Y S I O L O G Y V O L . 1 , N O . 5 , 2 0 1 5 Mantziari et al.O C T O B E R 2 0 1 5 : 4 1 1 – 2 0 Clinical Utility of Rapid High-Resolution Mapping

415

administration and was irrigated with a solution ofheparinized normal saline (1 U/ml) at a rate of1 ml/min throughout the procedure. There were noembolic complications, including stroke or systemicembolism. All catheters were checked and found to befree from any visible thrombus at the end of theprocedure. There were no bleeding complications orpericardial effusions. When during atrial mapping thecatheter inadvertently entered the right or leftventricle, it was easily pulled back with no events ofentrapment by the atrioventricular valves or theirsubvalvular apparati. Mapping of the LV did notaffect the aortic or mitral valve function as shown onpost-procedure echocardiography. In 4 cases, weused the transaortic approach to the left ventriclewith no thromboembolic complications or evidence ofdamage to the aortic root, the aortic valve, or coro-nary arteries. In case 17, the patient had previouslyundergone a Ross procedure for bicuspid aortic valvewith a pulmonary valve autograft in the place of theaortic valve. The retrograde approach and LV map-ping were also uncomplicated in that case.

ACCURACY OF MAPS. The acquired maps showedhighly detailed endocardial electrical activation. In

TABLE 2 Summary of Maps

Right Atrial Maps(n ¼ 30)

Left Atrial(n ¼ 22

Time (min) 10.5 (4.1–15.0) 10.8 (5.8–19

Accepted beats 540 (293–932) 758 (173–1,1

Electrograms 7,220 (3,467–10,947) 7,818 (4,379–

Values are median (range).

most cases, manual annotation was not necessary. Inonly 4 of 62 maps, manual annotation was performedin 16 of 70,862 points (0.02%). The main reasons forincorrect annotations were far-field ventricular elec-trograms around the valve areas and artifacts; how-ever, all points with incorrect annotation were easy toidentify on the high-density map as areas of inconsis-tent color coding to the adjacent areas (Figure 2).In atrial voltage maps, the threshold for the scar wasreduced to 0.5 to 0.05mV, and in some cases, reductionto 0.25 mV was applied in order to facilitate the iden-tification of gaps in linear lesions (Figure 3). In LVvoltagemaps, the standard cutoff value of<1.5mVwasapplied, but when the lower voltage cutoff was set to0.2mV, isthmuses of slow conductionwithin scar areaswere revealed. Three-dimensional basket and othercatheter localization was always in keeping with thefluoroscopic findings and highly internally consistent.

MAPPING OF SPECIFIC ARRHYTHMIAS. Typical atrialflutter was used as a known arrhythmic substrate tovalidate the system. An example is illustrated inFigure 3 and Online Video 1. Standard pulmonary veinisolation with wide area circumferential ablation andadditional activation/voltage maps of the LA beforeand after ablation was performed in patients with AF(n ¼ 8) (Online Figure 2). Patients with persistent AFalso had additional ablations (Table 2 shows details).Post ablation, 12 maps of the LA were acquired in 8.0(6.2 to 14.3) min, consisting of 7,818 (4,891 to 19,351)points, in order to assess entry block into pulmonaryveins, assess the linear lesions, or map an AT.Following persistent AF ablation, 5 gaps on linearlesions were identified and ablated successfully onthe site indicated by the system (Figure 4). Two casesof macro–re-entrant AT in patients with congenitalheart disease were studied, and gaps on previouslesions and/or atriotomy scars were identified as theisthmuses of slow conduction (Online Figure 3),followed by successful ablation (no inducibility oftachycardias). In total, 9 macro–re-entry ATs weremapped. The system mapped 100% of cycle length of8 ATs. In one case of short-lasting AT, the system wasable to map 69% of the cycle length.

Maps)

Left Ventricular Maps(n ¼ 10)

p ValueLA to RA/ LV to RA

.3) 36.6 (13.6–43.2) 0.98/<0.0001

75) 1,123 (288–1,732) 0.74/0.36

12,262) 8,709 (2,605–15,514) 0.79/0.81

http://jacccep.acc.org/video/2015/JEP031215_0073R_Video_1.mp4



FIGURE 2 Example of Incorrect Automatic Annotation

(A) The electrogram corresponding to the blue point (red arrow) is automatically annotated on the far field ventricular signal (V), because this

signal is larger than the near field atrial signal (A). Note that blanking of the V (red column) was set to avoid this error; however, it was too

narrow to cover the late V electrograms that appear close to the tricuspid annulus. The area of incorrect annotation (inside black box) on the

RA map is easily recognized as a spot of inconsistent color coding. (Right)Manual correction of the annotation is shown. This results in a change

of the color and shape of the point on the map that now appears as an orange ring. (B) Area of incorrect annotation (inside black box, magnified

in the middle) is shown as a spot of inconsistent color coding on the left ventricular map during ventricular tachycardia because of an artifact

that was mistaken for the QRS complex (V). RA ¼ right atrium.



416

VEs were mapped and ablated in 2 patients. In bothcases, the system created a template to the clinical VEand could accurately identify the clinical VE, acceptthe relevant beat, and annotate the signal automati-cally (Online Figure 4).

Three patients with sustained monomorphic VT werestudied (cases16, 17,and18).TheLVwasmappedusingthetransseptal (n ¼ 2) and transaortic (n ¼ 3) approaches.Mapping during VTwas performed in cases 16 and 17. Thesystem created the maps using a mapping window equalto the full cycle length of the tachycardia. Two macro–re-entry VTs were mapped in case 17 (100% of cycle length[CL] mapped), and one possible macro–re-entry VT wasmapped in case 16 (42% of CL was mapped). We observedthat mapping the full CL of the VT could result in errors inautomatic annotation because the system annotates thelargest electrogram within the mapping window, and this

can be either the local diastolic electrogram or the far fieldsystolic electrogram, whichever is larger (examples areshown in Figure 5A). To avoid this in case 16, we changedthe mapping window in retrospect to focus on the dia-stolic part of the VT. This revealed a figure-of-8-shapedre-entry VT in the inferobasal LV wall with correspond-ing diastolic potentials at the entrance and presystolicelectrograms at the exit. A substrate map of the LV wasperformed in sinus rhythm. The voltage threshold for scarwas set to 0.2 to 1.5 mV to reveal additional channels oflow voltage within the scar (Figure 5, Online Video 2).

DISCUSSION

To our knowledge, this is the first description of the initialclinical experience of a novel rapid high-resolution map-ping system in a variety of arrhythmias and substrates,



FIGURE 3 Typical Atrial Flutter

RA maps in the left anterior oblique (LAO) caudal view (case 11). (A) Voltage and activation map of the RA during typical counter-clockwise

atrial flutter (Online Video 1). (B) Voltage map after ablation on the CTI line shows low voltage along the line but a possible isthmus of

conduction. The activation mode of the same map shows a gap on the CTI line and conduction of the activation during CS pacing. Review of the

points on the site of the gap shows fractionated signal. (C) Voltage map after further ablation of the gap shows very low voltage along the line.

The time map confirms bidirectional blockage with widely split double potentials. CS ¼ coronary sinus; CTI ¼ cavotricuspid isthmus; EGM ¼electrogram; IVC ¼ inferior vena cava; RA ¼ right atrium; TV ¼ tricuspid valve.


417

including patients with acquired and congenital heartdisease. Briefly, the systemplatformwas user friendly andprovided clear and accurate localization of catheters, ge-ometry of cardiac chambers, and low-noise electrograms.The main advantages of the system were: 1) the high-resolution mapping of both activation timing and voltageinformation; 2) the short time required to acquire themaps; 3) the accurate automatic annotation; and 4) theability to change the mapping window in retrospect.

The mini-basket catheter does not require a balloon tobe deployed or additional stiff wire and sheath in order tobe positioned as other basket catheters do (5,6). It could beeasilymanipulated,deployed invariousdegrees fromzeroto maximum, and advanced in cardiac chambers,includingpulmonary veins (Online Figure 2), and the rightand left atrial appendages (Figure 4B) with no events ofcardiac perforation, valve damage, air embolism or visibleclot formation. Additionally, the mini-basket catheter

benefits from very closely spaced electrodes and acquisi-tion of contact electrograms. The obvious disadvantage ofhigh-resolution regional mapping is the need for sequen-tial data acquisition at multiple sites.

The maps we acquired in this cohort consisted of thou-sands of points acquired within a few minutes. Mappingwith previously available contact multipolar cathetersusually can create maps with a total of a few hundreds ofpoints that require manual annotation in order to bemeaningful (1,2). Previously, Nakagawa et al. (3) calculatedthe mean resolution of the maps that were automaticallyacquiredwith this systemwere2.6mm(1.8 to4.4mm).Thedetailed maps may have the potential benefit of revealingvaluable information with regard to the substrate.

We used the system in a variety of cardiac arrhyth-mias in order to explore its efficacy and potentialfuture utility. In this initial experience, we observedthat this system could accurately demonstrate gaps



FIGURE 4 Linear Lesions

(A) Focused map of the LA roof seen from above (superior view of the roof) during pacing from the LAA (the LAA is not shown on this map). The

local EGM at the site of the gap is 39 ms earlier to the reference (CS 7-8). (B) Additional ablation on the site (A) resulted in roof line blockage.

(B) Activation and voltage maps of the LA roof are shown with double potential on the roof line. (C) Focused map of the mitral isthmus area after

a mitral isthmus line was deployed. Activation map is shown during pacing from the LAA (case 13). A breakthrough of activation is seen in the

middle of the mitral isthmus line with the corresponding fractionated local EGM. The voltagemap below shows an isthmus of very low voltage on

the mitral line. The voltage on the gap is 0.068 mV. (D) Re-map of the mitral isthmus area in LAA pacing after further ablation shows no

endocardial conduction in the mitral isthmus and scarring along the line. However, there is still epicardial conduction over the CS. Further

ablation inside the CS resulted in MVI block. CS¼ coronary sinus; EGM¼ electrogram; LA¼ left atrium; LAA¼ left atrial appendage; LLPV¼ left

lower pulmonary vein; LUPV ¼ left upper pulmonary vein; MV ¼ mitral valve; MVI ¼ mitral valve isthmus; RUPV ¼ right upper pulmonary vein.



418

along the linear lesions (Figures 3 and 4), verifying theresults of Nakagawa et al. (3) in the experimentalmodel in canines. Limited ablation on the site of thegap shown by the system led to tachycardia termina-tion and/or achievement of block. The atrial voltagemaps might also provide useful information forpersistent AF ablation (7). The detail that this systemcan record with regard to the direction and velocity ofendocardial activation may be useful to map AF in thefuture, but this warrants further investigation.

In VT ablation, our initial experience showed thatthe basket catheter can be used to map the LV throughboth the transseptal and the retrograde approachesand can reach all areas inside the LV, althoughmanipulation was more challenging because of theventricular myocardial trabeculations and subvalvular

apparati. The longer time to acquire LV maps wasmainly attributed to the low frequency of VEs in 2cases. The automated QRS interval matching the clin-ical VE or VT was accurate in all cases, and the systemwas capable of rejecting the nonclinical ectopic beatsand correctly annotating the clinical ectopic beats.

The low-noise mini-electrodes can record signalsof very low voltage, and it is not clear whether thisimpacts the scar cutoff values. It was previouslyshown that endocardial areas with bipolar volt-age <1.5 mV correspond to myocardial scar (8,9).Pre-clinical evaluation of this system in a swine modelof ischemic scar showed that the same cut offof <1.5 mV correlated with scar on cardiac delayed-enhancement cardiac magnetic resonance imaging(CMR) (10). A pre-clinical study in dogs also showed

FIGURE 5 Left Ventricular Tachycardia

Maps are focused on the inferobasal LV wall. (A) Mapping of the full tachycardia CL (262 ms) shows a possible isthmus of conduction but the

right part of it is confusing (dashed white arrow). Magnification of this area shows a lot of points with different colors resulting from incorrect

annotation, see explanation in B. (B) The system automatically annotates the largest signal within the mapping window. When the mapping

window includes the systolic activation, and this happens to be larger than the local diastolic electrogram, then the system automatically

annotates the far field systolic potential (yellow dashed line). We can manually correct this by dragging the annotation to the near field signal

(blue dashed line). A more efficient way to avoid this is to shorten the mapping window to exclude the systolic and focus on the diastolic

part of the VT. (C) This map is automatically generated after we shortened the mapping window to 108 ms, focused on diastole, and it clearly

shows a figure-of-8-shaped ventricular tachycardia (Online Video 2) with early diastolic potentials at the entry site (1), mid-diastolic potentials

in the isthmus (2) and presystolic potentials at the exit site (3). (D) Substrate map of the inferobasal LV wall in SR. The scar threshold cutoff is

reduced to 0.2 mV to reveal isthmuses of low voltage within the scar area. CL ¼ cycle length; LV ¼ left ventricle; SR ¼ sinus rhythm.


419

that the size and location of scar mapped on electro-anatomical maps acquired with this system werehighly correlated with scar observed in CMR (11).However, looking further into scar at lower voltagesmay help to reveal channels of slow conduction andfacilitate the substrate mapping and ablation of VT.

One unique characteristic of this mapping systemwas that we could easily change the mapping windowretrospectively. By excluding the QRS interval andmoving the window of interest on the diastolic part ofthe CL during VT enabled the mapping of the localactivation along the critical isthmus of the VT thatoccurs during diastole (12,13). This feature requiresfurther validation in a larger study.

The mean procedure duration and fluoroscopytime of the studies presented in this paper seems to

be no shorter than usual for our institution (14), butthis is expected as we used the system to explore itspotential and future clinical use and there was alearning curve for the operators and cardiac physiol-ogists, therefore a direct comparison to previousstandard clinical practice was not attempted.

STUDY LIMITATIONS. A small number of patientswere included in this study, and a heterogeneousgroup of cases was described. A comparison to othermapping systems was not attempted at this stage dueto catheter/system incompatibilities and to allow fora learning curve. The current report is a description ofsequential cases rather than an experimental proto-col, and on clinical grounds, there was no opportunityto map the RV in these cases, although we would


PERSPECTIVES

COMPETENCY IN MEDICAL KNOWLEDGE: This

novel high-resolution mapping system can rapidly

acquire thousands of points and create very detailed

voltage and activation maps without the need for

manual annotation. Our first clinical observations have

shown that the system is safe and efficacious in

mapping the atria and the left ventricle in a variety of

arrhythmia substrates with the advantages of being

automatic and rapid. In addition it offers the ability to

the operator to review the maps and change the

mapping window in retrospect in order to focus on

areas of interest such as the diastolic part of the cycle

length during ventricular tachycardia.

TRANSLATIONAL OUTLOOK: The characteristics

of this novel system may improve our understanding

of the mechanisms of complex arrhythmias and

enhance the ablation outcomes but this warrants

further clinical research.



420

anticipate very simple manipulation in the RV and itsoutflow tract based on experience in other chambers.Similarly we did not use the system to performepicardial mapping, where additional complexitiesmay be encountered. We could not verify the accu-racy of the voltage maps because no scar informationfrom cardiac CMR was available. The system uses ahybrid magnetic and impedance location technology.Although no discrepancy was noted between thesystem and the fluoroscopic location of the catheters,this has not been formally validated.

CONCLUSIONS

The novel rapid, automatic mapping system was usedin a variety of human cardiac arrhythmias and provedto be both safe and efficacious. We were able to ac-quire detailed geometry of the cardiac chambers andhigh-resolution activation and voltage informationbased on automatic annotation. The system wascapable of mapping macro–re-entry tachycardias andassessing linear lesions with detailed information onslow conduction isthmuses, guiding the ablation forAF, creating detailed maps of the left ventricle duringsinus rhythm or VT and successfully selecting andautomatically annotating the clinical ventricularectopic beats. Its optimal use in specific tachycardiamapping and ablation warrants further research.

ACKNOWLEDGMENTS The authors thank Dr. KostasDimopoulos and Mr. Winston Banya for their assis-tance with the statistical analysis.

REPRINT REQUESTS AND CORRESPONDENCE: Dr.Tom Wong, Heart Rhythm Centre, NIHR CardiovascularBiomedical Research Unit, Institute of CardiovascularMedicine and Science, the Royal Brompton and HarefieldNHS Foundation Trust, Imperial College, Sydney Street,London SW3 6NP, United Kingdom. E-mail: [email protected].

RE F E RENCE S

1. Weerasooriya R, Jaïs P, Wright M, et al. Catheterablation of atrial tachycardia following atrialfibrillation ablation. J Cardiovasc Electrophysiol2009;20:833–8.

2. Jones DG, McCready JW, Kaba RA, et al. A multi-purpose spiral high-density mapping catheter:initial clinical experience in complex atrial arrhyth-mias. J Interv Card Electrophysiol 2011;31:225–35.

3. Nakagawa H, Ikeda A, Sharma T, Lazzara R,Jackman WM. Rapid high resolution electro-anatomical mapping: evaluation of a new systemin a canine atrial linear lesion model. Circ ArrhythmElectrophysiol 2012;5:417–24.

4. Ptaszek LM, Chalhoub F, Perna F, et al. Rapidacquisition of high-resolution electroanatomicalmaps using a novel multielectrode mapping sys-tem. J Interv Card Electrophysiol 2013;36:233–42.

5. Tai C-T, Liu T-Y, Lee P-C, Lin Y-J, Chang M-S,Chen S-A. Non-contact mapping to guide radio-frequency ablation of atypical right atrial flutter.J Am Coll Cardiol 2004;44:1080–6.

6. Arentz T, von Rosenthal J, Blum T, et al.Feasibility and safety of pulmonary vein isolationusing a new mapping and navigation system in

patients with refractory atrial fibrillation. Circula-tion 2003;108:2484–90.

7. Jadidi AS, Duncan E, Miyazaki S, et al. Func-tional nature of electrogram fractionationdemonstrated by left atrial high-density mapping.Circ Arrhythm Electrophysiol 2012;5:32–42.

8. Marchlinski FE, Callans DJ, Gottlieb CD, Zado E.Linear ablation lesions for control of unmappableventricular tachycardia in patients with ischemic andnonischemic cardiomyopathy. Circulation 2000;101:1288–96.

9. Reddy VY, Wrobleski D, Houghtaling C,Josephson ME, Ruskin JN. Combined epicardialand endocardial electroanatomic mapping in aporcine model of healed myocardial infarction.Circulation 2003;107:3236–42.

10. Tanaka Y, Genet M, Chuan Lee L, Martin AJ,Sievers R, Gerstenfeld EP. Utility of high-resolution electroanatomic mapping of the leftventricle using a multispline basket catheter in aswine model of chronic myocardial infarction.Heart Rhythm 2015;12:144–54.

11. Cokic I, Kali A, Wang X, Yang H-J, et al. Irondeposition following chronic myocardial infarction

as a substrate for cardiac electrical anomalies: initialfindings in a caninemodel. PLoSOne2013;8:e73193.

12. Stevenson WG, Soejima K. Catheter ablationfor ventricular tachycardia. Circulation 2007;115:2750–60.

13. Schneider HE, Schill M, Kriebel T, Paul T. Value ofdynamic substrate mapping to identify the criticaldiastolic pathway in postoperative ventricular re-entrant tachycardias after surgical repair of tetralogyof fallot. J Cardiovasc Electrophysiol 2012;23:930–7.

14. Mantziari L, Suman-Horduna I, Gujic M, et al.Use of asymmetric bidirectional catheters withdifferent curvature radius for catheter ablation ofcardiac arrhythmias. Pacing Clin Electrophysiol2013;36:757–63.

KEY WORDS atrial fibrillation, atrialtachycardia, electroanatomical mappingsystem, high-resolution mapping, ventriculartachycardia

APPENDIX For supplemental figures andvideos, please see the online version of thisarticle.

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