Is the Fascicle of Left Bundle Branch Involved in the Reentrant Circuit of Verapamil-Sensitive Idiopathic Left Ventricular Tachycardia?

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<ul><li><p>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</p><p>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)</p><p>ventricular tachycardia, electrophysiology, ablation</p><p>IntroductionVerapamil-sensitive idiopathic left ventricu-</p><p>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</p><p>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</p><p>Received November 12, 2002; revised January 10, 2003; ac-cepted January 15, 2002.</p><p>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.</p><p>Patients and MethodsPatient Characteristics</p><p>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.</p><p>1986 October 2003 PACE, Vol. 26</p></li><li><p>VERAPAMIL-SENSITIVE IDIOPATHIC LEFT VT</p><p>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.</p><p>Electrophysiological Study</p><p>All the patients gave written, informed con-sent. As described previously, electrophysiologi-cal study was performed while the patient was</p><p>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.</p><p>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,</p><p>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.</p><p>PACE, Vol. 26 October 2003 1987</p></li><li><p>KUO, ET AL.</p><p>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.</p><p>Catheter Ablation</p><p>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-</p><p>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.</p><p>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.</p><p>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</p><p>1988 October 2003 PACE, Vol. 26</p></li><li><p>VERAPAMIL-SENSITIVE IDIOPATHIC LEFT VT</p><p>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.</p><p>Postablation Follow-Up</p><p>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.</p><p>ECG Criteria for Fascicular Block</p><p>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 &lt; 0.12 seconds.12,13</p><p>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 &lt; 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</p><p>Statistical Analysis</p><p>Quantitative data were expressed as mean SD. Parametric data were compared with t-test,</p><p>Table I.Clinical Features and Electrocardiographic Characteristics in Patients with Left Fascicular Blocks During Sinus Rhythm</p><p>SR VTGroup I QRSD-B QRSD-A Transition QRSD-VT TransitionPt. No. Age Sex Axis (ms) (ms) Zone Axis (ms) Zone</p><p>1 27 M LAD 110 110 V3V4 RAD 153 V2V32 19 M LAD 118 120 V3V4 I 155 V2V33 20 M LAD 110 108 V3V4 LAD 160 V2V34 30 M LAD 115 112 V2V3 I 135 V2V35 35 M RAD 110 110 V1V2 I 135 V1V26 14 F RAD 90 92 V5V6 RAD 155 V2V37 25 M RAD 87 90 V4 I 120 V1V28 43 M RAD 85 85 V3V4 I 135 V2V39 26 M RAD 110 108 V2V3 I 130 V3V4</p><p>10 20 M RAD 110 110 V2V3 I 135 V2V311 20 M RAD 100 100 V2V3 LAD 140 V2V3</p><p>F = female; I = indeterminate axis; LAD = left-axis deviation; M = male; QRSD = duration of QRS complex during ventriculartachycardia; QRSD-A = duration of QRS complex during sinus rhythm after ablation; QRSD-B = duration of QRS complex during sinusrhythm before ablation; RAD = right-axis deviation; SR = sinus rhythm; VT = ventricular tachycardia.</p><p>and categorical data were analyzed by the chi-square test with Yates correction or Fishers ex-act test. P &lt; 0.05 was considered statisticallysignificant.</p><p>ResultsCharacteristics of VT Patients with Left Anterioror Posterior Fascicular Block (Table I)</p><p>The mean duration of QRS complex during si-nus rhythm before and after RF catheter ablationand during VT were 104 12 ms, 104 11 ms, and141 13 ms, respectively. The transitional zonesof QRS complexes in the precordial leads duringsinus rhythm were at or before V3 in five (45%)patients, and after V3 in six (55%) patients. Thetransitional zones of QRS complexes in the pre-cordial leads during VT were at or before V3 in ten(91%) patients, and after V3 in one (9%) patient.The transitional zones of QRS complexes in theprecordial leads during VT were earlier (54.5%),equal to (36.6%), or later (9.1%) than those of dur-ing sinus rhythm.</p><p>Characteristics of VT Patients Without LeftFascicular Block (Table II)</p><p>The mean duration of QRS complex duringsinus rhythm before and after RF catheter abla-tion, and during VT was 95 11 ms, 95 10 ms,and 140 14 ms, respectively. The transitionalzones of QRS complexes in the precordial leadsduring VT were at or before V3 in 18 (47%) patientsand after V3 in 20 (53%) patient. The transitional</p><p>PACE, Vol. 26 October 2003 1989</p></li><li><p>KUO, ET AL.</p><p>Table II.Clinical Features and Electrocardiographic Characteristics in Patients Without Left Fascicular Blocks During Sinus Rhythm</p><p>SR VTGroup II QRSD-B QRSD-A Transition QRSD-VT TransitionPt. No. Age Sex Axis (ms) (ms) Zone Axis (ms) Zone</p><p>1 30 M N 100 100 V3V4 LAD 124 V3V42 41 M N 90 88 V2V3 LAD 120 V5V63 69 M N 87 90 V2V3 RAD 126 V1V24 57 M N 86 90 V3V4 RAD 143 V1V25 26 M N 100 96 V3V4 I 140 V3V46 16 F N 100 100 V2V3 LAD 152 V2V37 19 M N 100 102 V1V2 I 135 V2V38 27 M N 78 80 V3V4 I 148 V3V49 29 M N 110 108 V3V4 LAD 150 ALL +</p><p>10 26 M N 82 85 V3V4 I 160 V2V311 45 M N 100 96 V2V3 I 150 V2V312 32 M N 94 98 V3V4 LAD 139 V2V313 8 F N 98 100 V4V5 LAD 120 V2V314 15 F N 77 80 ALL+ I 120 V2V315 31 M N 90 86 V2V3 LAD 118 V316 8 F N 94 94 V2V3 I 139 V3V417 53 M N 94 96 V3V4 I 155 V2V318 34 M N 110 108 V1V2 I 155 V2V319 32 M N 95 96 V3V4 RAD 114 V5V620 38 M N 98 100 V1V2 I 145 V3V421 25 F N 98 96 V4 I 140 V2V322 38 M N 105 100 V3V4 LAD 120 V2V323 28 M N 69 70 V2V3 LAD 151 V1V224 16 M N 118 116 V4V5 I 155 V1V225 26 M N 85 90 V3V4 LAD 151 V1V226 57 F N 102 100 V3 I 155 V2V327 67 M N 90 90 V3V4 LAD 155 V5V628 34 M N 110 105 V3V4 I 145 V2V329 30 M N 95 100 V2V3 I 130 V2V330 32 F N 87 90 V2V3 LAD 138 V2V331 76 M N 90 88 V2V3 I 158 V3V432 57 F N 115 110 V3V4 I 145 V4V533 18 M N 102 100 V2V3 LAD 130 V2V334 36 M N 82 80 V2V3 I 125 V1V235 34 M N 100 96 V3V4 LAD 158 V2V336 22 F N 106 104 V2V3 LAD 126 V2V337 46 M N 88 86 V4V5 I 150 V2V338 35 M N 82 82 V3V4 I 131 V1V2</p><p>See Table I for definitions.</p><p>zones of QRS complexes in the precordial leadsduring VT were at or before V3 in 27 (71%) pa-tients and after V3 in 11 (29%) patients. The tran-sitional zones of QRS complexes in the precor-dial leads during VT were earlier (47.4%), equal to(26.3%), or later (26.3%) than those of during sinusrhythm.</p><p>Comparisons of Patients BetweenGroups I and II (Table III)</p><p>Mean age and sex were similar between groupI and group II patients. The duration of QRScomplex during sinus rhythm before and afterRF catheter ablation in group I patients was sig-nificantly longer than that of group II patients</p><p>1990 October 2003 PACE, Vol. 26</p></li><li><p>VERAPAMIL-SENSITIVE IDIOPATHIC LEFT VT</p><p>Table III.Comparisons of QRS Complex Duration and Precordial Transitional Zone Between Two Groups</p><p>Precordial TransitionalZone During VTQRSD-B QRSD-VT QRSD-A</p><p>(ms) (ms) (ms) V1V3 V3V4</p><p>Group I 104 12 141 13 104 11 10 (91%) 1 (9%)Group II 95 11 140 14 95 10 27 (71%) 11 (29%)P value 0.02 0.78 0.007 P &gt; 0.05</p><p>Values are expressed as mean SD, number, or percentage (in parenthesis). See Table I for definition.</p><p>(104 12 vs 95 11 ms, respectively, P = 0.02before RF catheter ablation; 104 11 ms vs 95 10 ms, respectively, after RF catheter ablation). Theduration of QRS complex during VT was similarbetween group I and group II patients (141 13ms vs 140 14 ms, respectively, P = 0.78). Tran-sitional zones of QRS complexes in the precor-dial leads during VT were similar between groupI and group II patients. After ablation, QRS du-ration did not prolong in group I or group IIpatients (104 11 ms vs 95 10 ms, respec-tively); fascicular block did not happen in group IIpatients.</p><p>Discus...</p></li></ul>

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