Journal of Interventional Cardiac Electrophysiology 11, 135–141, 2004C© 2004 Kluwer Academic Publishers. Manufactured in The Netherlands.

Comparison of Presystolic Purkinje and Late DiastolicPotentials for Selection of Ablation Site in IdiopathicVerapamil Sensitive Left Ventricular Tachycardia

Arash Arya, Majid Haghjoo, Zahra Emkanjoo,Amir Farjam Fazelifar, Mohammad RezaDehghani, Alireza Heydari, and Mohammad AliSadr-AmeliDepartment of Pacemaker and Electrophysiology, RajaieCardiovascular Medical Center, Mellat Park, Vali Asr Avenue,Tehran, 1996911151, Iran

Abstract. Background: Idiopathic verapamil-sensitiveleft ventricular tachycardia (ILVT) is the most commonform of idiopathic left ventricular tachycardia (VT). Dif-ferent methods have been proposed for ablation of ILVT.

Methods: Between June 2002 and February 2004, 15patients (12 men; age 28 ± 11 years, range 12 to 51) withILVT underwent radiofrequency (RF) ablation at ourcenter. We retrospectively assessed the significance ofrecording purkinje potential (PP) and late diastolic po-tential (DP) and its effect on selection of ablation targetand number of RF application.

Results: Sixteen VTs were observed. The clinical VThad either RBBB and left axis morphology (14 cases)or RBBB and right axis morphology (2 cases). The QRSduration during tachycardia was 124 ± 12 ms and thetachycardia cycle length was 356 ± 53 ms. DP and PPwere recorded at the targeted area for RF ablation in11 and 9 patients respectively. The PP-Q interval, DP-Qinterval and DP width were 18 ± 4, 53 ± 18 and 14 ±8 ms, respectively. The number of RF application was7.2 ± 4.3. Fewer applications were needed in whom RFablation was initially targeted to PP (with or withoutDP) recording site (10 patients, 4.7 ± 1.8) compared tothose targeted to DP recording site (5 patients, 12.2 ±3.3) (P < 0.05).

Conclusion: Compared to DP alone, earliest PP (withor without concomitant DP) might be superior for selec-tion of target site of RF ablation in patients with ILVT.

Key Words. ventricular tachycardia, potentials,catheter ablation, mapping

Introduction

Idiopathic verapamil-sensitive ventricular lefttachycardia (ILVT) is the most common form of id-iopathic left ventricular tachycardia (VT) [1]. ThisVT usually occurs in young patients with struc-turally normal heart. Most patients experience re-current episodes of sustained VT but the rate ofrecurrence varies from patient to patient. The 12lead ECG during sinus rhythm (SR) usually shows

no specific finding. The right bundle branch block(RBBB) with left axis deviation variant of ILVTwas first described by Zipes et al. in 1979 [2]. Ver-apamil sensitivity of this VT was revealed by Bel-hassen and his colleagues [3]. Subsequently, Oheet al. [4] and Shimoike et al. [5] described the othertwo variants (RBBB with right axis deviation andupper septal variant, respectively) of ILVT. Macro-reentry with an excitable gap has been proposedas the underlying mechanism of ILVT [6,7]. Thedemonstration of entrainment criteria supportsreentry as the mechanism of this tachycardia [8,9].

Radiofrequency (RF) catheter ablation is highlysuccessful in ILVT. Different methods have beenproposed for ablation of ILVT. RF ablation attachycardia exit site, where the pace map 12-leadECG displays a QRS configuration matching thatduring the tachycardia, is first described by Wenet al. [10]. Nakagawa and his colleagues reportedfor the first time the significance of sharp purkinjepotential (PP) in ablation of ILVT [11]. Tsuchiyaet al. [12] described the significance of late di-astolic potential (DP) in arrhythmia circuit andselection of ablation target site in this VT. How-ever, their successful ablation sites were differentfrom each other. While Wen’s ablation sites wereat the inferoapical septum in the LV, Tsuchiya’ssuccess sites were at basal septal region close tothe main trunk of left bundle branch. Tsuchiyaand co-workers [12], Aiba et al. [13] and Nogamiet al. [14] showed the role of PP and DP in thearrhythmia circuit of ILVT. In the present study

Address for correspondence: Arash Arya, M.D., Departmentof Pacemaker and Electrophysiology, Rajaie CardiovascularMedical Center, Mellat Park, Vali Asr Avenue, Tehran, Iran.E-mail: arya@rhc.ac.ir

Received 18 May 2004; accepted 8 July 2004

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136 Arya et al.

Fig. 1. Twelve lead surface electrocardiogram showing idiopathic verapamil sensitive left ventricular tachycardia with RBBBand left axis morphology (A) and RBBB and right axis morphology (B).

the role of recording PP and DP and its effect onselection of successful ablation site and number ofRF application are retrospectively assessed.

Methods

Patients. Between June 2002 and February2004, a total of 15 patients with ILVT were re-ferred to our centre and underwent RF ablation.ECG during arrhythmia (Fig. 1) showed RBBBand left axis deviation in 14 and right axis devia-tion in 2 cases (one patient had both variations).These patients were 12 men and 3 women with themean age of 28 ± 11 years (range 12–51 years).All but one patient (the case number 3 had tachy-cardia induced cardiomyopathy) had structurallynormal heart. ILVT terminated with intravenousverapamil in all cases. All patients who were in-cluded in the study gave written informed consentfor the procedures of EP study and RF catheterablation. Table 1 shows characteristics of our pa-tients and their arrhythmia.

Electrophysiologic Study. All antiarrhyth-mic medications were withdrawn before EP studyfor five half lives. Three quadripolar catheters (6F,Josephson, Bard Electrophysiology) were intro-duced via femoral veins and positioned at RV apex

(and right ventricular outflow tract), His bundleand high right atrium. A 7F steerable decapo-lar catheter (2-5-2 mm) was introduced via leftfemoral artery (Marinr, Medtronic Inc, MN, USA)and positioned in LV on interventricular septumfor recording intracardiac signals (especially PPand DP potentials). This catheter was used as aguide for localization of DP-PP recording site andearliest ventricular activation site (EAS) by ab-lation catheter. A 7F ablation catheter (Conductr,Medtronic Inc, MN, USA) was introduced via rightfemoral artery and positioned on LV septum formapping and subsequent RF ablation. Figure 2Aand B show the position of the catheters in the leftventricle.

Twelve lead surface ECG and bipolar filteredelectrograms (30–500 Hz) and unipolar unfilteredelectrograms were recorded, displayed, and storedon an electrophysiologic recording system (EPmedsystem Inc., USA). Bipolar electrical stimulationwas performed from the distal two electrodes ofablation catheter and the RVOT catheter, respec-tively (current strength 10 mA, pulse duration2 msec). Mapping was done during SR and VT.Programmed electrical stimulation with two ba-sic drive cycle lengths (600 and 400 ms) and upto three extrastimuli was done for VT induction.Mapping during VT was done to delineate EASand DP-PP recording sites.

Selection of Ablation Target in ILVT 137

Table 1. Clinical features and electrocardiographic characteristics

Patient Age Sex VT Morphology QRSd∗ TCL∗∗ Follow-Up¶

1 25 M LAD 125 350 242 21 M LAD 148 270 233 12 M LAD 131 330 204 36 M LAD 116 420 185 22 M LAD 121 320 176 13 F LAD 110 360 167† 45 M LAD 147 410 148 32 M LAD 109 350 119 51 M RAD 123 290 10

10 22 F LAD 118 330 811‡ 42 F LAD/RAD 139 440 812 18 M LAD 124 370 613 30 M LAD 119 320 414 27 M LAD 121 450 315 30 M LAD 110 330 2

Mean ± SD 28 ± 11 124 ± 12 356 ± 53 12 ± 7

∗QRS duration during tachycardia (ms).∗∗Tachycardia Cycle length (ms).¶Months.†The arrhythmia recurred 2 weeks after 1st ablation.‡In 1st RF ablation session VT with LAD morphology was ablated successfully targeting earliest PP. Ablation of 2nd VT with RAD morphology failedwith conventional method. We localized EAS with EnSite©R in upper septum and targeted it for ablation which was successful.LAD: left axis deviation, RAD: right axis deviation.

In two cases with previously failed conventionalRF ablation the endocardial non-contact activa-tion mapping with EnSite©R 3000 system (Endocar-dial Solutions Inc., USA) was done (Fig. 2C andB) [15–17]. In brief a 7.5 mm 64 electrode array(balloon) is used to create 3000 virtual electrodes.These noncontact intracavitary virtual electrodescan be used to detect potential field on the endo-cardial surface. Once the voltage field has beenestablished, activation points can be displayed aselectrograms or as isopotential maps. A three-step process of establishing geometry, identifyingthe area of interest, and navigating the ablationcatheter to this area is used to map and treat ar-rhythmias.

Anticoagulation with heparin was done andACT (ACT II, Medtronic Inc. USA) was keptthroughout procedure between 250 and 350 sec.

Radiofrequency Catheter Ablation Proce-dure. An Attakr II (Medtronic Inc. USA) RF en-ergy generator was used. RF energy was applied(50–60 W, 70◦C) from distal electrode of ablationcatheter during VT and if it was successful within15 seconds it was continued for 60 seconds.

In 10 patients PP was recorded (with or with-out concomitant DP). In these cases the targetsite of RF ablation was earliest PP recording site.In the remaining five patients the only recordedpotential was DP and RF ablation targeted toDP recording site. When VT was terminated dur-ing RF ablation, the inducibility of VT was as-sessed with programmed and burst pacing proto-

col before and after isoproterenol infusion (Up to4 µg/min). Thirty minutes after the final RF en-ergy application, the inducibility of VT was againassessed.

Follow-Up. Follow-up was done at our outpa-tient arrhythmia clinic. Patients were assessed forpossible VT recurrence by clinical symptoms, ECG(12 lead and/or holter monitoring) in all cases. Nopatient was lost to follow-up.

Data Description and Analysis. Continuousvariables are expressed as mean ± SD and/orrange and discrete variables are expressed as per-centage. The significance of difference betweengroups was assessed by the independent sampleStudent’s t test. A level of P < 0.05 was acceptedas statistically significant.

Results

Patient CharacteristicsBetween June 2002 and February 2004, 15 pa-tients (12 men; age 28 ± 11 years, range 12 to51) with ILVT underwent RF ablation at our cen-ter (Table 1). The patients received 1-3 antiar-rhythmic drugs before admission with variableresponse. All the cases but one (case 3) had no ev-idence of structural heart disease.

Patient number 3 presented with recent on-set and progressive dyspnea on exertion. Atransthoracic echocardiography (TTE) showed

138 Arya et al.

Fig. 2. (A) Schematic illustration of catheter positions for ablation of ILVT with respect to potential recording sites. (B)Fluoroscopic view of mapping and ablation catheters in LV for ablation of ILVT in right anterior oblique (RAO) view. (C) and (D)shows the purkinje and diastolic potentials recording site and earliest ventricular activation site (EAS) on interventricular septumin RAO view, respectively. Note the difference in location between these two sites which signifies the size of re-entrant circuit in ILVT.Black arrow points to the EnSite©R balloon.

increased cardiac sizes, LV ejection fraction(LVEF) = 30% and moderately severe mitral re-gurgitation (MR). EP study was done and con-firmed the diagnosis of ILVT with 2:1 ventriculoa-trial block. RF energy delivered during tachycar-dia at PP recording site (50 w-70◦C, 60 sec) andwas successful at termination and prevention ofinduction of ILVT. Three months after ablation aChest X-ray was done and normal. A repeated TTEat the same visit revealed normal cardiac sizes,LVEF = 65% and trivial MR.

Patient number 13 had coincidence of ILVTwith atrioventricular nodal reentrant tachycar-dia (AVNRT). The patient had history of frequentepisodes of palpitations and sustained narrowcomplex tachycardia. During electrophysiologicstudy two arrhythmias, one with narrow com-plexes which shown to be AVNRT and the otherwith wide QRS complexes and right bundle branchblock and left axis morphology, compatible with

ILVT, were inducible. Radiofrequency catheter ab-lation of both arrhythmias was done at two consec-utive sessions.

Arrhythmia CharacteristicsAll patients but case number 13 (see above), haddocumented spontaneous clinical VT. The meanQRS duration during tachycardia was 124 ± 12 msand the mean tachycardia cycle length was 356 ±53 ms. The clinical VT had either RBBB and leftaxis morphology (14 cases) or RBBB and right axismorphology (2 cases).

The clinical arrhythmias in case number 11(Table 1) had two different patterns, a wide QRStachycardia with RBBB and left axis deviationmorphology and another with RBBB and rightaxis deviation morphology. The electrophysiol-ogy study localized the origin of tachycardias tothe midinferior and superior ventricular septum,respectively.

Selection of Ablation Target in ILVT 139

Fig. 3. (A) Intracardiac electrograms at successful site of RF ablation of ILVT. White and black arrow point to DP and PP onablation catheter, respectively. Note the same potentials visible on LV mapping catheter. (B) Sequence of recorded PP during sinusrhythm on LV mapping catheter. Note DP on LV 7–8 and 9–10 bipolar recordings. (C) White and black arrow shows DP and PP onablation catheter, respectively. LV1-2 to 9-10: bipolar recordings from decapolar left ventriclar mapping catheter, Abl: ablationcatheter, Abl-uni: unipolar recording from ablation catheter, RVA: right ventricular apex.

Electrophysiology StudyLeft ventricular mapping during VT revealed theEAS in inferoapical septum (14 cases) or superiorseptal region (2 cases). The activation time was−21 ± 5 ms compared to the onset of QRS complexduring tachycardia.

The characteristics of the recorded potentialsduring VT at the targeted area for RF ablationwere as follows: DP and PP were recorded in 11and 9 patients respectively (Fig. 3). The PP-Q in-terval, DP-Q interval and DP width were 18 ± 4,53 ± 18 and 14 ± 8 ms, respectively (Table 2). ThePP was recorded during SR in all patients on de-capolar LV mapping catheter but the sequence wasreverse to that seen during VT. Mechanical termi-nation of VT was observed in DP-PP recording sitein 4 patients.

Radiofrequency Catheter AblationSeventeen sessions of RF ablation was done in 15patients. In all patients RF ablation was success-ful and the ILVT terminated and became nonin-ducible. In patient number 9 and 11 RF ablationwas successful after second attempt.

The number of RF applications was 7.2 ± 4.3(Table 2). When the number of RF applicationswas compared between patients in whom RF abla-tion was initially targeted to DP recording site (5

patients, 12.2 ± 3.3) and those to PP (with or with-out DP) recording site (10 patients, 4.7±1.8), fewerapplications were needed in the latter (P < 0.05).No complication but one groin hematoma occurredin our patients.

Follow-UpThe patients were followed for an average of 12 ±7 months (range 2–24 months). All the patientswere visited regularly at our outpatient clinic. Nopatient lost to follow up. No antiarrhythmic medi-cation was administered after RF ablation. All thepatients remained asymptomatic throughout fol-low up period.

Discussion

Main FindingWe found two type of successful ablation site inour patients. In five patients in whom the success-ful site was chosen solely by DP, the number of RFenergy applications was 12.2 ± 3.3. In the remain-ing patients the number of RF applications was4.7±1.8. RF ablation was successful in all patients.This finding suggests that although ablation wassuccessful in all patients, fewer applications wereneeded in those whose ablation was targeted toearliest recorded PP on ablation catheter.

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Table 2. Characteristics of recorded potentials at targeted area and RF ablation results

Patient DP PP DPW∗ DP-Q∗ PP-Q∗ EAS∗ No of RFs

1 Y N 12 33 – 21 122 Y N 21 35 – 18 83 N Y – – 8 19 44 Y Y 23 38 13 24 55 Y N 14 55 – 31 106 N Y – – 14 17 47 Y Y 25 45 – 11 98 Y Y 18 95 19 16 39 Y N 16 75 – 23 15

10 Y Y 17 64 15 21 511 Y N 21 40 – 28 1612 Y Y 13 54 4 18 513 N Y – – 31 23 614 Y Y 15 54 16 26 415 N Y – – 10 14 3

Mean ± SD 18 ± 4 53 ± 18 14 ± 8 21 ± 5 7.2 ± 4.3

∗Intervals are expressed in ms.DP: diastolic potential, PP: purkinje potential, DPW: diastolic potential width, DP-Q: Interval between DP to the onset of earliest QRS complex, PP-Q:Interval between PP to the onset of earliest QRS complex, EAS: earliest ventricular activation compared to the onset of earliest QRS complex, Y: yes,N: no.

Different methods have been proposed for abla-tion of ILVT. Ablation at the exit site, where thepace map 12-lead ECG displays a QRS configu-ration matching that during the tachycardia, isfirst described by Wen et al. [10]. Nakagawa et al.[11] described the significance of purkinje poten-tial in the ablation of ILVT. In the successive 16patients, Tsuchiya et al. [12] compared the resultsof RF catheter ablation between the two patientgroups: In the initial 7 patients (Group 1), RF en-ergy was applied to the earliest LV activation siteor PP recording site in the posteroapical LV sep-tum, and in the other 9 patients (Group 2), it wasto the DP recording site. When the number andtotal energy of RF energy applied were comparedbetween the two groups, both parameters were sig-nificantly smaller in latter.

DP is not recordable in all patients with ILVT.Nogami et al. [14] showed that in 15 of the 20patients, RF catheter ablation was successful atthe site with a DP that is distant from the VTexit. In the remaining five patients (25%), theDP could not be detected during VT, but the ap-plication of RF current to a single fused PP wassuccessful.

The exact nature of reentrant circuit in ILVTis not fully elucidated. Kottkamp et al. [18] sug-gest that it is a micro-reentry circuit in the re-gion of the left posterior fascicle. Nogami et al.[14] hypothesized that in ILVT circuit, DP repre-sents the activation potential in the distal portionof the specialized Purkinje tissue (slow conductionzone), and that has decremental properties andverapamil-sensitivity. The PP represents the acti-vation potential of the left posterior fascicle or of

the Purkinje fiber near the left posterior fascicle.Contrary to this, Kuo et al. [7] showed that fascicleof the left bundle dose not involve in the arrhyth-mia circuit. There is a link between DP and PP.During VT, PP was activated in the reverse direc-tion. This explains why the activation sequencesof PP were reversed during SR and VT.

Other Findings. Case number eleven pre-sented with both morphologies of ILVT. Although,two different morphologies of this VT convertedeasily to each other, RF ablation at midinferiorseptum terminated only VT with RBBB and leftaxis morphology and second pattern remainedinducible. More detailed mapping by noncontactmapping in another session revealed the EAS insuperior portion of septum. RF ablation at thatsite terminated the VT with RBBB and right axismorphology. This rare combination can be ex-plained by either two separate re-entrant circuitsor a single circuit with two widely separated exitsites.

Study Limitation. Critical potentials after theQRS complex should be differentiated from T-wave, P-wave and bystander purkinje potentials.These potentials related to the VT circuit can bedifferentiated from bystander potentials by atrialor ventricular pacing and entrainment mapping.The QT interval is shortened during pacing; how-ever, the H-DP interval is usually prolonged [14].Although we differentiated DP from T-wave andP-wave by atrial and ventricular pacing, the lowerefficacy of DP for choosing RF application site com-pared to PP in our study might be related to that

Selection of Ablation Target in ILVT 141

we did not verify the recorded DP by entrainmentmapping in all cases.

ConclusionOur study suggests that although ablation wassuccessful in all patients, fewer applications wereneeded in those whose ablation was targeted toearliest recorded PP (with or without DP) on ab-lation catheter. Before using DP for choosing tar-get site for RF ablation, it should be differenti-ated from T-wave, P-wave and bystander poten-tials by atrial or ventricular pacing and entrain-ment mapping.

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