Util ity of NoninvasiveArrhythmia Mapping in

Patients with AdultCongenital Heart Disease Sabine Ernst, MD, FESCa,b,*, Johan Saenen, MDa,Riikka Rydman, MDa, Federico Gomez, MDa,Karine Roy, MDa, Lilian Mantziari, MDa,Irina Suman-Horduna, MDa

KEYWORDS

� Congenital heart disease � Catheter ablation � Anatomy � Three-dimensional mapping� Noninvasive � Outcomes

KEY POINTS

� Previous body surface mapping approaches lacked integration of the individual anatomy, andtherefore have rarely been used in clinical practice in the last decade.

� A recently introduced noninvasive multielectrode electrocardiographic mapping system (ECVUE;CardioInsight Technologies Inc, Cleveland, OH, USA) combines 3-dimensional (3D) reconstructionof the cardiac anatomy from computed tomography scans with simultaneous recording of the car-diac activation from 252 surface electrocardiographic electrograms.

� The noninvasive nature of the 3D multielectrode mapping system helped to differentiate multipletargets in some patients or rare ectopy over a longer mapping time of several hours.

� Documentation of the location of the critical substrate allowed an informed choice regarding con-ventional versus remote-controlled navigation techniques, which in turn resulted in limited proce-dure time and radiation exposure.

� The 3D multielectrode mapping system helped avoid the unnecessary risk of an invasive procedurein patients with palpitations resulting from sinus tachycardia.

INTRODUCTION

Arrhythmia management in patients with adultcongenital heart disease (ACHD) is a challengeon many levels, as tachycardic episodes maylead to hemodynamic impairment in otherwisecompensated patients even if episodes are onlytransient.1,2 Arrhythmias are in all the differenttypes of congenital cohorts a marker for

The authors have nothing to disclose.a Department of Cardiology, Royal Brompton Hospital, Sycular Biomedical Research Unit, Royal Brompton and Hareperial College London, Sydney Street, London SW3 6NP,* Corresponding author. Royal Brompton and HarefieldCollege London, Sydney Street, London SW3 6NP, UK.E-mail address: s.ernst@rbht.nhs.uk

Card Electrophysiol Clin 7 (2015) 117–123http://dx.doi.org/10.1016/j.ccep.2014.11.0071877-9182/15/$ – see front matter � 2015 Elsevier Inc. All

significant morbidity and mortality.2–6 Owing tothe underlying condition, challenges can presentin various aspects such as the corrected anatomicsituation after surgery, the inherent conductionproperties of a potentially abnormally located orotherwise impaired conduction system, and thearrhythmia substrate itself in the form of fibrosisand/or surgically acquired scars.7 This presenta-tion may give rise to a multitude of arrhythmia

dney Street, London SW3 6NP, UK; b NIHR Cardiovas-field Hospital, National Heart and Lung Institute, Im-UKHospital, National Heart and Lung Institute, Imperial

rights reserved. cardiacEP.th

eclinics.com

Table 1

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substrates, which can vary from infrequent atrialor ventricular ectopy to sustained reentrant tachy-cardias.3,8–10 Some congenital conditions, suchas Ebstein anomaly, have a high incidence of mul-tiple accessory pathways, giving rise to atrioven-tricular (AV) reentrant tachycardia; this mayinclude several accessory pathways or the normalconduction system, resulting in variable AV reen-trant circuits, which can confuse the invasive elec-trophysiologist and increase the complexity of anycatheter ablation procedure.11,12 However, asACHD patients are usually young and active mem-bers of society, any curative approach to their ar-rhythmias leads to a dramatic change in theirclinical course such that catheter ablation is advo-cated in preference to lifelong antiarrhythmicmedication by many interventional electrophysiol-ogists. Recently several technical advances,including 3-dimensional (3D) image integration,3D mapping, and remote magnetic navigation,have been introduced to facilitate curativelyintended ablation procedures in this special pa-tient cohort.13–15 This review attempts to outlinethe role of a novel technology of simultaneous,noninvasive mapping in this patient cohort, andgives details of the authors’ single-centerexperience.16–18

Demographics of patients with adultcongenital heart disease

No. of patients 14

Age (y) 32.8 (24.6–47.4)

Gender 9 F, 5 M

Underlying heartdisease

1 D-TGA 1 arterial switch2 CCTGA1 AVSD1 LSVC 1 mitral valvedisease

1 DiGeorge syndrome2 Coarctation of the aorta2 Fontan2 Ebstein1 Double-chambered RV 1VSD repair

1 ASD repair

Previous ablation 9 (6 AT/AF, 1 WPW, 2 VE)

Spontaneousablation target

9

Provocationduring EP study

12

Abbreviations: ASD, atrial septal defect; AT/AF, atrialtachycardia/atrial fibrillation; AVSD, atrioventricularseptal defect; CCTGA, congenitally corrected transposi-tion of the great arteries; D-TGA, dextro-transposition ofthe great arteries; EP, electrophysiology; LSVC, left supe-rior vena cava; RV, right ventricle; VE, ventricular ectopy;VSD, ventricular septal defect; WPW, Wolff-Parkinson-White syndrome.

SIMULTANEOUS VERSUS SEQUENTIALMAPPING

To allow successful catheter ablation, a detailedunderstanding of the arrhythmia and the exactlocalization of the critical substrate (eg, focalsource of the arrhythmia or critical isthmus of areentry) needs to be identified.7,19 Although bodysurface electrocardiogram (ECG) mapping hasbeen available for a long time, most invasive map-ping systems have used a sequential recordingapproach, which requires a stable arrhythmia.15,20

Any infrequent, irregular, or unstable arrhythmia isessentially “nonmappable” using a sequentialapproach, as the activation pattern is constantlychanging. Moreover, infrequently occurring ar-rhythmias that are difficult to provoke under cath-eter laboratory conditions pose a challenge in theelectrophysiology (EP) laboratory, as the physio-logic conditions of the sympathetic drive mightbe diminished, especially if invasive proceduresrequire sedation of the patient.Body surface mapping approaches of the past

lacked the integration of the individual anatomy,and therefore have been used rarely in clinicalpractice in the last decade. The recent intro-duction of the noninvasive multielectrode ECGmapping (ECM) system (ECVUE; CardioInsightTechnologies Inc, Cleveland, OH, USA) has now

closed this gap.17,18 It combines the 3D recon-struction of the cardiac anatomy from computedtomography (CT) scans with the simultaneousrecording of the cardiac activation from 252 sur-face ECG electrograms. Using an inverse solution,virtual unipolar electrograms are reconstructed onthe epicardial surface of either the atrial or ventric-ular chambers. This panoramic mapping systemallows assessment of a global activation sequencefrom a single beat in a noninvasive fashion. Its useso far has been reported in patients with atrial orventricular tachycardia, accessory pathwaydependent tachycardia, and atrial fibrillation.

METHODSPatient Population

Of a total cohort of 27 patients undergoing ECM atthe authors’ institution from November 2012 toMay 2013, 14 had an underlying ACHD condition.Table 1 gives an overview of the detailed condi-tions. Patients were recruited from the waiting listfor invasive EP studies and gave consent for thenoninvasive mapping study using the ECM in addi-tion to the invasive EP procedure. In cases of rare

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or transient arrhythmias, all antiarrhythmic drugswere discontinued for at least 3 times the elimina-tion half-life, whereas patients with persistentarrhythmia were rate-controlled only. If present,oral anticoagulation was paused 1 day before theprocedure.

Preacquired Computed Tomography ImageAcquisition and 3-Dimensional Reconstruction

A thoracic, noncontrast CT scan (Somatom;Siemens, Forchheim, Germany) was acquiredwith the multielectrode vest attached to thepatient, firstly to exactly locate the surface elec-trodes and secondly to reconstruct the 3D anat-omy of the atrial or ventricular chambers.Landmarks including the atrioventricular valves,left anterior descending artery (LAD), and posteriordescending artery (PDA) were added to facilitateorientation for the operator.

For each heart beat the ECM generated 1500unipolar electrograms on the 3D epicardial recon-struction of the heart, giving rise to color-codedisopotential, voltage, and propagation maps. Themaximal negative slope of the local electrogramsdetermined the activation time, allowing the gener-ation of isochronal and directional activationmaps.

Arrhythmia Recording Using NoninvasiveElectrocardiographic Mapping

In all cases, patients underwent a recording periodon the ward to document their clinical arrhythmiaoutside the catheter laboratory. In case of rare ortransient palpitations, several maneuvers were at-tempted to provoke arrhythmias, including bicycleexercise, vagal stimulation, and hyperventilation. Ifthe patient remained noninducible, pharmacologicprovocation was attempted with isoprenaline infu-sion and/or atropine injection.

Details of the Invasive ElectrophysiologyStudy

Patients with inducible or spontaneously occurringarrhythmias were brought to the EP laboratory.Depending on the underlying heart disease, typeof arrhythmia, and the necessity to exclude intra-cardiac thrombi by transesophageal echocardiog-raphy, the procedure was performed under localanesthetic, sedation, or general anesthesia asper institutional standards.

At the beginning of the EP study, conventionalprogrammed stimulation was carried via diag-nostic catheters to evaluate the basic electricalproperties. In the case of sustained spontaneousor induced arrhythmia, appropriate conventionalpacing maneuvers were performed to ascertainthe critical isthmus, and all conventional

electrograms were recorded on a conventionalrecording system (Siemens AG, Forchheim,Germany) in parallel with the ECM recordings. Ifdeemed necessary by the operator, the remote-controlled navigation system Niobe (StereotaxisInc, St Louis, MO, USA) was used in conjunctionwith the ECM system. Details of this system havebeen described previously13,14 for patients withnormal or congenital heart disease.

RESULTS

A total of 14 patients with ACHD (mean age 37.4 �18.3 years, 9 female) underwent noninvasive map-ping using the ECM in preparation for their EPstudy. Diagnosis of ACHD ranged from left atrialisomerism to tricuspid atresia with right atrium,pulmonary artery Fontan operation, aortic coarcta-tion, and arterial switch for dextro-transposition ofthe great arteries (see Table 1). Only 5 patientshad no previous ablation attempt while the major-ity had failed at least 1 previous sequential EPstudy.

Noninvasive Multielectrode Mapping Outsidethe Catheter Laboratory

Half of the patients presented with ongoing orspontaneously occurring arrhythmia (Fig. 1), and6 of the arrhythmias originated from the ventricularmyocardium and 7 from the atrium, respectively.One patient demonstrated overt preexcitation ofa posterolateral accessory pathway in the pres-ence of Ebstein anomaly. In 5 patients, additionalmeasures were taken to induce any arrhythmia;these included physiologic maneuvers (handgrip, Valsalva), physical activity (rapid pacewalking, riding a stationary bicycle), or pharmaco-logic provocation with isoprenaline infusion oratropine bolus. One case with previously docu-mented ventricular ectopics was found to be non-inducible and was referred to the EP laboratorysince a 12-lead ECG of the clinical ventricularectopic morphology had been documentedearlier, and 1 case was excluded from furtherstudy because no arrhythmias were observed atbaseline and nothing other than sinus tachycardiacould be induced by exercise or pharmacologicprovocation. The accelerated sinus rhythm corre-lated well with the clinical symptoms of these pa-tients, who had undergone several ablationprocedures previously, such that no further inva-sive EP approach was pursued.

In Vivo Localization of the Ablation Target

As the ECM is not a navigation system in theclassic sense, no depiction of the ablation catheter

Fig. 1. Example of a 29-year-old female patient with tricuspid and pulmonary atresia. Five different prematureatrial contractions (PACs) were mapped and successfully ablated. Red shows earliest breakthrough; blue/purpleshows late activation. AP, anteroposterior; CAU, caudal; CRA, cranial; IVC, inferior vena cava; LA, left anterior;LAA, left atrial appendage; LIPV, left inferior pulmonary vein; LSPV, left superior pulmonary vein; MV, mitralvalve; PA, posteroanterior; RA, right atrium; RAA, right atrial appendage; RAO, right anterior oblique; RIPV, rightinferior pulmonary vein; RL, right lateral; RSPV, right superior pulmonary vein; SVC, superior vena cava.

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localization is available. Navigation toward theablation target is helped by iterative spike orpace-mapping techniques. In the first case, pacingis required via the mapping catheter and encom-passes the epicardial mapping of the pacing spikewith the ECVUE.21 As only the site of earliest acti-vation is informative for revealing the position ofthe mapping catheter, only the pacing spike isused for this approach. Moreover, pace matchwas visually evaluated to compare the isopotentialmap of the paced beat with that of a spontaneousbeat (Fig. 2). The substrate of interest was furtherconfirmed by classic entrainment and pace-mapping maneuvers. The ECM guided the posi-tioning of the mapping catheter while probing forpositive entrainment and perfect pace match,and showed great precision as warming up wasobserved on radiofrequency (RF) application inmany of the designated target areas.

Combination of Magnetic Navigation andECVUE

In many patients with ACHD, the use of the mag-netic navigation system has been advantageousin overcoming access problems, as reportedrecently.14,22 In these studies, the authors electedto use the remote magnetic navigation combinedwith ECVUE-guided mapping in 4 patients. To thebest of their knowledge, this is the first report ofthe combination of remote magnetic navigationwith the ECM platform. The advantages to this pa-tient cohort are evident, as the ECM allows fastarrhythmia mapping regardless of accessibility oranatomic complexity together with remote naviga-tion, further reducing radiation exposure andenhancing access to less favorable anatomy suchas corrected congenital heart disease. In the au-thors’ experience, the magnetic field does not

Fig. 2. Spontaneous ventricular ectopic and iterative pace map to locate the focal origin using the ECM in com-bination with remote magnetic navigation. Ao, aorta; HIS, His recording electrodes; LAO, left anterior oblique;Mag, magnetic mapping and ablation catheter; PA, pulmonary artery; PM, pace map; PVC, premature ventricularcontraction; RAO, right anterior oblique; RF, radiofrequency; RV, right ventricle/ventricular; TV, tricuspid valve.

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causenoise after themagnetic vector hasmoved, orinterference that precludes the use of the ECVUEplatform.

Outcome of ECVUE-Guided Ablation inPatients with Adult Congenital Heart Disease

All but 1 patient finally were studied invasively, withonly 5 patients under general anesthesia and theremainder under assisted sedation by a dedicatedcardiac anesthetic team. Procedure durationamounted to a median 188 minutes (interquartilerange 164–237 minutes). Median fluoroscopyduration was 14.7 minutes (interquartile range11.6–21.1 minutes) with a median of 20 RF appli-cations. In 9 patients multiple arrhythmias werethe target, which was greatly facilitated by thesimultaneous mapping system. At follow-up (me-dian of 18 months), 9 of 14 patients were in sinusrhythm while 3 experienced further arrhythmiasdespite antiarrhythmic medication. Of the 2 pa-tients who were noninducible (1 on the wardwithout an invasive EP study and 1 who remainednoninducible despite invasive EP study), both re-ported further nonsustained palpitations.

DISCUSSION

The recently introduced 3D noninvasive ECMsystem has the potential to overcome some of

the limitations that hamper current ablation proce-dures.16–18 The system overcomes several limita-tions that are currently not addressed bysequential mapping systems. First, this platformallows prolonged bedside monitoring in a noninva-sive fashion and in more physiologic conditions. Itallows one to challenge the patient with “commonlife situations” such as exercise or interaction withstaff and relatives. This approach is extremelyhelpful especially during transient events, whenpatients can identify their typical symptoms. Inthe absence of any inducible or targetablearrhythmia, ECM was able to document, forexample, sinus tachycardia (which for some pa-tients is very symptomatic), thereby negating theneed for further invasive procedures.

Furthermore, as the system requires a singlebeat to create a complete activation map, theECM platform allows mapping of multiple arrhyth-mias in a limited time frame. It therefore is espe-cially suitable for patients with congenital heartdisease who often present with multiplearrhythmias. Hence in most patients the nature,number, and localization (ie, right- vs left-sidedchamber, endo- vs epicardial surface) of thearrhythmia targets was identified even before thepatient entered the EP laboratory, which is advan-tageous to procedural planning and execution,and prevents unnecessary risk of complications.

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Despite the complexity of the underlying dis-ease and the multitude of arrhythmias that werepresent in these patients, an overall acute successof 75% in a congenital heart disease cohort isimpressive (excluding the noninducible patientsfrom the analysis). Similar success rates were ob-tained for both atrial and ventricular arrhythmias. Inthe authors’ hands, the combination with remotemagnetic navigation is feasible and did not inter-fere with the operation of the ECM platform. Infact, it provided a further opportunity to reduce ra-diation exposure and allowed the operator to posi-tion the catheter in a stabilized fashion withoutrisking dislodgment during the ECM analysis.

LIMITATIONS

The number of patients included in this study ismodest; however, complex cases with extensiveACHD and multiple arrhythmias have been ad-dressed here, making this novel technology atleast an additional option to be considered in thischallenging patient cohort. Better 3D reconstruc-tion algorithms, especially for complex surgicallycorrected patients, are needed to allow better“road-map” guidance during the invasive part ofthe study.

SUMMARY

This article reports on the use of the ECM systemfor patients with ACHD for the treatment of bothatrial and ventricular arrhythmias. In particular,the noninvasive nature of the 3D mapping processon the ward helped to differentiate multiple targetsin some patients, or rare ectopy over a longer map-ping time of several hours. Documentation of thelocation of the critical substrate then allowed aninformed choice on conventional versus remote-controlled navigation techniques, which in turn re-sulted in limited procedure time and radiationexposure. This approach helped avoid the unnec-essary risk of an invasive procedure in patientswith palpitations caused by sinus tachycardia.

ACKNOWLEDGMENTS

The authors are indebted to Cheng Yao, PhD,who expertly supported the noninvasive and inva-sive part of these studies, as well as the prepara-tion of the figures.

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