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  • Is the Fascicle of Left Bundle Branch Involvedin the Reentrant Circuit of Verapamil-SensitiveIdiopathic Left Ventricular Tachycardia?JEN-YUAN KUO,* CHING-TAI TAI, CHERN-EN CHIANG, WEN-CHUNG YU,JIN-LONG HUANG, MING-HSIUNG HSIEH, CHARLES JIA-YIN HOU,*CHENG-HO TSAI,* YU-AN DING, and SHIH-ANN CHENFrom the *Division of Cardiology, Department of Medicine, Mackay Memorial Hospital, Taipei Medical University,Taipei, Division of Cardiology, Department of Medicine, National Yang-Ming University, School of Medicine, AndVeterans General Hospital-Taipei, Taipei, Division of Cardiology, Department of Medicine, Wan-Fang Hospital,Taipei Medical University, Taipei, and the Division of Cardiology, Department of Medicine, Veterans GeneralHospital-Taichung, Taichung, Taiwan

    KUO, J.-Y., ET AL.: Is the Fascicle of Left Bundle Branch Involved in the Reentrant Circuit of Verapamil-Sensitive Idiopathic Left Ventricular Tachycardia? The exact reentrant circuit of the verapamil-sensitiveidiopathic left VT with a RBBB configuration remains unclear. Furthermore, if the fascicle of left bundlebranch is involved in the reentrant circuit has not been well studied. Forty-nine patients with verapamil-sensitive idiopathic left VT underwent electrophysiological study and RF catheter ablation. Group I in-cluded 11 patients (10 men, 1 woman; mean age 25 8 years) with left anterior fascicular block (4 patients),or left posterior fascicular block (7 patients) during sinus rhythm. Group II included 38 patients (29 men,9 women; mean age 35 16 years) without fascicular block during sinus rhythm. Duration of QRS com-plex during sinus rhythm before RF catheter ablation in group I patients was significant longer than thatof group II patients (104 12 vs 95 11 ms, respectively, P = 0.02). Duration of QRS complex duringVT was similar between group I and group II patients (141 13 vs 140 14 ms, respectively, P = 0.78).Transitional zones of QRS complexes in the precordial leads during VT were similar between group I andgroup II patients. After ablation, the QRS duration did not prolong in group I or group II patients (104 11 vs 95 10 ms, P = 0.02); fascicular block did not occur in group II patients. Duration and transitionalzone of QRS complex during VT were similar between the two groups, and new fascicular block did notoccur after ablation. These findings suggest the fascicle of left bundle branch may be not involved in theantegrade limb of reentry circuit in idiopathic left VT. (PACE 2003; 26:19861992)

    ventricular tachycardia, electrophysiology, ablation

    IntroductionVerapamil-sensitive idiopathic left ventricu-

    lar tachycardia (VT) with a right bundle branchblock (RBBB) configuration and left-axis devia-tion occurs predominantly in young male patientswithout structural heart disease. This VT wasdemonstrated to be due to reentry with an excitablegap and a slow conduction area. Radiofrequency(RF) ablation of idiopathic left VT can be guided bypacemapping, earliest presystolic Purkinje poten-tial (PP), or a diastolic potential (DP) during idio-pathic left VT.110 However, the exact reentrant cir-cuit of the verapamil-sensitive idiopathic left VTwith a RBBB configuration remains unclear. Fur-thermore, if the fascicle of the left bundle branchis involved in the reentrant circuit has not beenwell studied. If the left fascicles were involved in

    Address for reprints: Shih-Ann Chen, M.D., Div. of Cardiol-ogy, Veterans General Hospital-Taipei, 201, Sec. 2, Shih-PaiRoad, Taipei, Taiwan. Fax: 886-2-2873-5656; e-mail: epsachen@ms41.hinet.net

    Received November 12, 2002; revised January 10, 2003; ac-cepted January 15, 2002.

    the antegrade limb of reentry circuit, the durationof the QRS complex during sinus rhythm wouldbe prolonged, and the new fascicular block wouldoccur after the successful ablation. The aim of thisstudy was to compare the duration of the QRS com-plex before and after RF catheter ablation betweenpatients with and without a left hemiblock in sinusrhythm.

    Patients and MethodsPatient Characteristics

    Between July 1992 and September 2001,48 patients who had symptomatic monomorphicVT without recognizable structural heart diseasewere referred for electrophysiological study andRF ablation. Group I included 11 patients (10 men,1 woman; mean age 25 8 years) with left anteriorfascicular block (4 patients) or left posterior fascic-ular block (7 patients) during sinus rhythm (Figs. 1and 2). Group II included 38 patients (29 men,9 women; mean age 35 16 years) without fas-cicular block during sinus rhythm (Fig. 3). All pa-tients had clinically documented recordings of VTbefore referral.

    1986 October 2003 PACE, Vol. 26

  • VERAPAMIL-SENSITIVE IDIOPATHIC LEFT VT

    Figure 1. Tracings obtained from case 1.Twelve-lead electrocardiogram record-ings during (A) sinus rhythm, (B) ventric-ular tachycardia, and (C) sinus rhythmafter radiofrequency catheter ablation ina case with left anterior fascicular block.

    Electrophysiological Study

    All the patients gave written, informed con-sent. As described previously, electrophysiologi-cal study was performed while the patient was

    Figure 2. Tracings obtained from case 5. Twelve-leadelectrocardiogram recordings during (A) sinus rhythm,(B) ventricular tachycardia, and (C) sinus rhythm afterradiofrequency catheter ablation in a case with left pos-terior fascicular block.

    fasting and not sedated, and all antiarrhythmicmedications were discontinued for at least 5 half-lives before study. Details of the electrophysiolog-ical study have been described previously.24,7,11Three 6 Fr quadripolar electrode catheters (USCI,

    Figure 3. Tracings obtained from case 38. Twelve-leadelectrocardiogram recordings during (A) sinus rhythm,(B) ventricular tachycardia, and (C) sinus rhythm afterradiofrequency catheter ablation in a case without fas-cicular block.

    PACE, Vol. 26 October 2003 1987

  • KUO, ET AL.

    Billerica, MA, USA or Mansfield, Boston ScientificCorp., Watertown, MA, USA) were positioned inthe high right atrium, His-bundle area, and rightventricle via the femoral veins. Programmed stim-ulation was performed with atrial burst pacing,atrial single extrastimulus, ventricular burst pac-ing, or using up to three ventricular extrastimuliat two ventricular pacing cycle lengths (400 and600 ms) from the right ventricular apex, outflowtract, or left ventricle with delivery of stimuli attwice the diastolic threshold and 2-ms pulse dura-tion. Isoproterenol infusion (14 g/min) was usedto facilitate the induction of VT if tachycardia wasnot inducible in the baseline state.

    Catheter Ablation

    Two methods were used to identify the tar-get site for ablation. Endocardial activation map-ping was performed during VT to identify the siteof earliest activation relative to the onset of theQRS complex with a sharp PP (Fig. 4). Pacemap-ping was done during sinus rhythm by pacingat the same rate as the clinical VT to obtain anidentical QRS morphology (Fig. 5). An optimalpacemapping was defined as a 12-lead electro-cardiograph (ECG) showing at least a match of11 leads with the QRS morphology of the clini-

    Figure 4. Tracings obtained from case 38 showing theintracardiac electrogram at the successful site duringventricular tachycardia. A Purkinje potential (arrow-heads) of 16 ms preceding the onset of the surface elec-trocardiogram. ABL = ablation catheter; HRA = highright atrium; PCS = proximal coronary sinus; RVA =right ventricular apex.

    Figure 5. Tracings obtained from case 16. Twelve-leadelectrocardiogram recordings during (A) ventriculartachycardia and (B) pacemapping from the distal bipo-lar electrodes of the ablation catheter at the suc-cessful site with the same cycle length of ventriculartachycardia.

    cal VT. A 7 Fr quadripolar electrode catheter witha 4-mm distal electrode, interelectrode space of2 mm, deflectable curve, and thermistor-embeddedtip (Mansfield or EP Technologies, Inc., Sunny-valle, CA, USA) was used for ablation under fluo-roscopy. RF current (generated from the Radionics-3C, Radionics, Burlington, MA, USA, or EPT-500,1000, EP Technologies, Inc.) was delivered be-tween the tip electrode and a standard adhesiveelectrosurgical dispersive pad applied to the pos-terior chest wall. RF energy was delivered with a

    1988 October 2003 PACE, Vol. 26

  • VERAPAMIL-SENSITIVE IDIOPATHIC LEFT VT

    power range of 3050 W (or temperature setting of6070C) and a pulse duration of 3060 seconds.Successful ablation was defined as complete abo-lition of VT.

    Postablation Follow-Up

    As previously described, all patients were ob-served in the intensive care unit and were moni-tored by ECG for 24 hours. After discharge fromthe hospital, patients returned to the outpatientclinic at 2 weeks, 1 month, and subsequently ev-ery 24 months. If the patients experienced palpi-tation, another 24-hour Holter monitoring or car-diac event recording was used to evaluate thesesymptoms.

    ECG Criteria for Fascicular Block

    Left anterior fascicular block was defined asthe (1) frontal plane mean QRS axis of 45 to 90degrees; (2) rS patterns in leads II, III, and aVF,and a qR pattern in leads I and aVL; and (3) QRSduration < 0.12 seconds.12,13

    Left posterior fascicular block was defined as a(1) right-axis deviation greater than + 120 degrees;(2) rS pattern in leads I and aVL with qR patternsin inferior leads; (3) QRS duration < 0.12 seconds;and an (4) exclusion of other factors causing right-axis deviation (e.g., right ventricular overload pat-terns, lateral infarction).12,13

    Statistical Analysis

    Quantitative data were expressed as mean SD. Parametric data were compared with t-test,

    Table I.Clinical Features and Electrocardiographic Characteristics in Patients with Left Fascicular Blocks During Sinus Rhythm

    SR VTGroup I QRSD-B QRSD-A Transition QRSD-VT T

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