15CC Vel . la. Nn. 7 1767 D- robe, 1991 :1767-A

Radiofrequency Catheter Ablation for Treatment of Bundle Branch Reentrant Ventricular : Results and Long-Term Follow-Up TODD J . COHEN . MD, WALTER W . CHIEN . M D . KEITH G . LURIE, MD, CHARLIE YOUNG, MD, FACC . HAROLD F . GOLDBERG, MD, FACC, YIN-SHI W ANG . M D. JONATHAN J . LANGBERG, MD. FACC, MICHAEL D. LESH . MD, FACC, MICHAEL A . LEE, MD, JERRY C . GRIFFIN, MD . FACC . MELVIN M . SCHEINMAN . MD, FACC San Francisco, California

Seven of 120 consecutive patients with inducible sustained ventric . vclve with the distal electrode tip of the catheter near the right ular tachycardia (from September 1 . 1988 to January 1, 1991) had bundle branch . One to three applications of continuous nemndu- bundle branch reentrant tachycardia and underwent percutane . lated radiofrequency current at 300 kHz between the distal tuts radiofrequency ablation of the right bundle branch. The seven electrode and a large posterior skin patch resulted in complete patients had been unsuccessfully treated with a mean of 3 ± t right in all patients, after which none had drugs. Four patients presented with and three with inducible bundle branch reentrant tachycardia on restudy. On aborted sudden death. The baseline electrocardiogram revealed a restudy, three of the seven patients had ventricular tacbycardia of left bundle branch black pattern in three patients and an intro. myocardial origin (not bundle branch reentry). One patient ventricular conduction defect in four. required no therapy ; drug re defibrillator therapy was used in the The baseline HV interval was prolonged in each case (79 z others. After a mean follow-up Interval of 12 ± 3 months (range 2 ms). With use of programmed ventricular extrastim li . sus- 6 to 29) complete right bundle branch black persisted, there were tained bundle branch reentrant tachycardia was inducible in all no spontaneous episodes of venh tcular tachycardia and no patient patients at a mean cycle length of 283 ± 17 ms (range 230 to 350) . required a permanent pacemak :r, Bundle branch reentrant tachycardia characteristics included Radiofrequency catheter a?tatinn of the right bundle branch L atelovemricular dissociation, a Hit deflection time preceded each easily performed and is a safe a :d effective treatment for bundle QRS complex and spontaneous His to His variation that preceded branch reentrant lachyca•d ia. It is probably the procedure of changes in ventricular lachycardia cycle length . choice for these highly symptomatic patients. A quadripolar catheter was positioned across the tricuspid (J Am Coll Card:x11991 :18.1767-73)

In 6% of patients with inducible (II. Methods bundle branch reentry has been reported as the mechanism . Study patients . Between September I, 1988 and January Direct current catheter ablation of the right bundle branch I, 1991 . 7 of t20 consecutive patients were identified as has been successful in interrupting the macroreentrant cir- having inducible sustained ventricular tachycardia due to a cuit (2-4) . Recently, Langberg et al . at our institution bundle branch reentrant mechanism . Table I shows the described a case in which mdiofrequency ablation produced right bundle branch block and eliminated bundle branch incidence of bundle branch reentrant tachycardia in various reentrant tachycardia, In the present study, we report a patient categories with inducible sustained ventricularlachy- long-term follow-up of seven patients who underwent radio- cardia over this period. Table 2 shows the characteristics of frequency catheter ablation of the right bundle branch to our seven patients with bundle branch reentrant tachycardia . cure ventricular :achycardia due to bundle branch reentry . Patient I was described in a previous report (5) . The mean age of the group was 62 ; 6 years (34 to 72) and the mean left ventricular ejection fraction was 23 . 3% (9% to 35%). All From the Department of Medicine and the Cu diavascular Research were male . Four patients were admitted with syncope and tentacle, University of California . San Francisco . California, This report was three with aborted sudden death (ventricular tachycardia or presenlnd in part al the IXlh World Congress oe Catheter Ablation on Stay 29 . 1991 in Washington, D.C. Dr. Cohen is mpponed by Grant HLO8174 Gam the ventricelar requiring cardioversion or defibrilla- National Institutes of Health . aethesda. staryland. lion). Four patients had ischemic with Manuscript received April 17. 1'991 : revised manuscript received June 25, severe three-"essel coronary disease with prior myocardial 1991,accepudluly 17, 1991 . Address for reminh : Melon M . Seheinman, htD, Room T:, H Mu infarction, one had , one had idio- Hospital, Box 0124, University ufCelifornia . San Francisco. California 94141 pathic and one had liv

©1991 by the American Cotlcrc of Cardmlugy 0735-11197i91r5J .5n

1768 COHLN I:'1' At . JAr(' Vnl. I5 . N,, 7 ItAUIOPRLQCINI'y 010 .ATION FOR iiNii r BRANCH REENTRANT TA('HYCARDIA nccemner 1991 :17W7-71

Table I, Cardiac Diagnosis in 1'_0 Consecutive Ral-1, With tachycardia compared with conducted complexes : and 5) in Inducihle Sustained Ventricular Iachpcardia selected cases premature right ventricular apical depolariza- nm, Patient, 1-de- of 3TCF lions delivered during inscription of the His bur:dle resulted luh,lraK 1'il InnJ in termination of the tachycardia 11 .71 . In addition . the His to con ;mu, distort as 4.5 right bundle branch conduction time during tachycardia was Codion„ walby IR 157 the same or shorter than His to right bundle branch conduc- No-it Iemnae' s a tion time at baseline . Aonic calve replacement t The fdlnsring trailnrnrdias mere di(ferentiated,frotn han- n,n genn :d neon di,ea.e uichlrenoicol;,rdy,plnrio 1 a dle branch reentrant tachycardia (I) : II supraventricular "final Ctl 5.8 tachycardia with aberrancy ; 2) tachycardia originating from ventricular muscle ; 3) fascicular tachycardia: and 4) antidru- - Sepod . right ventricular omflau at and eamcholamine-induced sea mcular .ohycanlia. BBRT - bundle brmtcch h feentrant Inchycurdial mic tachycardia using a Mahaim tract . Technique of radiofrequency ablation of the right bundle branch . This study was approved by the Institutional Re- cardinmyopathy. Two (Patients 3 and 6) had a pacemaker view Board of the University of California . San Francisco that had been implanted because of syncope or intermittent and each patient gave informed consent . A 6F or 7F steer- trifascicular block, or both . In all patients the able quadripolar catheter with a 3-mm distal tip and I-cm proved refractory to a mean of 3 ± I antiarrhythmic drugs interelectrode spacing (Mansfield Scientific) or a custom- (range I to 7) . designed steerable bipolar catheter with a distal tip 4 mm in Baseline electrophysiologic study . Each patient under- length and 2-mm interelectrode spacing (USCI) were used went electrophysiologic study with programmed electrical for right bundle branch ablation . The catheter was posi- stimulation to assess the inducihility and the mechanism of tioned across the to record a His bundle tachycardia. Three electrode catheters were inserted electrogram . 11 was then advanced to record a right bundle through the femoral vein into the right atrium, low right atrial branch potential from the distal two poles . septum and against the right ventricular apex, respectively . Criteria far detection of a right handle branch potential Standard programmed electrical stimulation was performed included 1) a sharp deflection occurring ?20 ms after the His with use of up to three extrastimuli from two right ventric- deflection. and 2) no atrial electrogram present on the right ular sites. An induction protocol with use of pauses (6) bundle branch electrogram recording (see Fig . 2( (8). Con- (short-long-short induction sequence) was required for tinuous unmodulated radiofrequency current at 300 kHz, tachycardia induction only in Patient 7 . Bundle branch delivered by a radiofrequency generator (model RFG-3B, reentry was scorched for during each study . Radionics) was applied to the region of the right bundle Bundle hrancit reentrant toelivtordia revs identified on branch during the baseline rhythm (sinus rhythm in six the basis of the tattooing criteria : I) atrioventricular (AV) patients and in one) . Applications of radio- dissociation occurred during ventricular tachycardia ; 21 a frequency were administered at 15 to 20 W and for up to 60 s His or right bundle branch deflection, or both, preceded each or until an increase in impedance occurred . The radiofre- QRS complex ; 3) spontaneous His to His and right bundle quency energy was applied between the distal electrode in branch to right bundle branch cycle length variations pre- the right ventricle and a large posterior skin patch . A repeat ceded a change in ventricular tachycardia cycle length :41 the electrophysiologic study was performed in each patient after duration of the HV interval was the same or longer during ablation during the same procedure .

Table 2 . Characteristics of Seven Men With Bundle Branch keenuanI Tachvcardia Bundle Hmnch Neeporc t Tachyeardio' Pt Age Drugs Failed No. tyrl Symptom Diagnosis FFthl ECG CL tmsl .Axis INr .I RFNo . FT I 6.1 ASD CAD 9 IVCD 270 Sup I 29mu( 77 Syncope All, CM HI lVCD 210 Sup I 1 AIW, 14 no, 3 79 Syncope CAD 21) LBBB 330 [of 4 3nrcn 55 Syncope CAD 25 LBBB 230 lot I I Alw. 14 inn 53 Syncope CAD IVCD 280 tel' 5 I A/w.11)mn 72 ASD IDCM 2 5 LBBB 350 Inf 7 I A/w, 7 mo 7 Mw. 5 ma 34 ASD HChI 35 IVCD 2% Sup I I 'All of these tach1'cardias hod i umhguruliun . - Died of crones unrelated to the procedure . AIc CM = alcoholic cardiosn opathv ASD = ahnrted .sudden daalh : .ASS' - olive amt out : CAD = cn v anery disease : CL = cycle length : ECG - eleotrocaNiogram : EF = ejeclie. free ion . F)L'=follow-up:HCM=hyprm'ophiccardiomyopathy :IDCht ridiupulhicdihnedcardiomyopathy :Inf=interior : IVCD=intravemricularconductiundefecl : LBBB = lea bundle branch block : M = male : PI = Patient. NF - radiofrequency ablation procedure, : Sup - superior .

Iii'( Vn1 . IP. Nu.7 ET AL . 1769 Ihc-1, 14917767 71 In .AUI11rat9ct I' .5 5 Ahl.11 VI1 Pop Ht ,1111 1-. PIi-1NC11 orFNTNANT "T"'CACas s I- A

r V1 -~ 1

I II\ ~~~. _ Figure 1. Patient 1. Baseline hods surface F 1 / electrocardiograms I ECUs) end intracardiac elcctrograms. His handle potential IH I and right bundle ranch (RBI potentials arc 'maltaneuusly recorded . The HV interval HBEPO--j . ~, .---uo was prolonged al 10 ms' . A right bundle I branch potential IVI is recorded 35 ms after HY=6 1'r H-RB= 5ms ; '1 11 the His bundle potential (H). A = etrial electrogram : HBE = His bundle electro- w~-R,1d1 P`a~ gram; RV = right ventricular electrogram . V = ventricular electrogram .

I

Patient follow-up . After ablation, each patient had a 24 It Results Holler ambulatory electrocardiographic IECGI monitor i1e- Samman of seven cases . Baseline ECGs showed a left fore hospital discharge . In addition . each patient was in- intracentucular conduction defect in four patients and a structed to contact our clinic immediately fur am' recurrence complete left bundle branch `lock pattern in three . The of symptoms . All patients were seen in our baseline HV interval was prolonged in all patients (mean 79 arrhythmia clinic at I month follow-up and then followed up 2 ms. range 65 to 85). Sustained bundle branch reentrant at 3 month intervals . A history . physical examination and tachycardia was inducible with use of standard programmed 12-lead ECG were obtained at that time . The patients were ventricular sdmulalion in all patients . m Patient 7 a pause recontacted by phone and their current medical statas re- viewed. protocol facilitated induction of bundle branch reentrant Statistical analysis. The chi-square test was used to com- tachycardia. The mean tchycardia cycle length was t283 '- pare the incidence of bundle branch reentrant tachycardia in 17 ms Irange 210 to 350). patients with with that in patients A tiplat e (Puff-t4) is illrstrtned irr Figures I mtd?. with cardiomyopathy. A Student's unpaired t test was used Figure I shows simultaneous recordings of surface BUG and to compare the electrophysiologic characteristics after ra- intracardiac elcctrograms. Figure 2 shows intracardiac re- diofrequency ablation of the right bundle branch with those cordings during bundle branch reentrant tachycardia in this at baseline . A p value < 0 .05 was considered statistically patient . Note the presence of AV dissociation and His to His significant . All data are presented as mean vslues ~ SE. variation that preceded a change in ventricular tachycardia

II Figure 2. Patient 4. Bundle branch recn- tram) Gchvcardia w-as induced at u ventricular cycle length of Nit ms . Auto- ventricular dissociation was present trot 230 240 1 2 ;,o 2110 illustrated) and His to His 1 H-HI sanmior - 1 I N precedes changes in tachycardia aclc MM length . In addition . the His to right bundle branch III-RBI conduction time shortened I~X-Ri 2 ms I I 1 during handle branch reentrant tachccar- I ael ,el - ng ae, Au di ;Nfrom 35 to 25 msl . Abhreciatioro a% in Frill ^~ 1~ "~ " f Figure I . I V xao V zao~V z Vl d zaa IVV'z"a~aY1V In by IV II

1I I . If I I IIIII I I I 1 1 1 I III 1 IIIII I 'fl I It lii IJ Maui nhi I

1770 CO HEN ET AL. JACC VAL IN, No. 7 RADIOFREQUENCY ABLATION FOR BUNDLE BRANCH REENTRANT TACHYCARDIA Dn ,nbn, 17)Li 767-73

Figure 3 . Patient 3. The baseline 12-lead electrocar- diogram (ECG) shows a left bundle branch block pattern . Bundle branch reentrant tachycardia (BBRT) was inducible with a right inferior axis and left bundle branch block configuration at a ventricular cycle length of 330 ms . Radiofrcqucncy ablation (Post Ab- Iationl resulted in complete right bundle branch block, after which bundle branch reentrant tachycardia was no longer inducible . VA

cycle length . His to right bundle branch conduction time resulted in complete right bundle branch block in all pa- during bundle branch reentrant tachycardia was less than at tients . Table 3 shows the electrophysiologic characteristics baseline . before and immediately after radiofrequency ablation of the It is important to emphasize that multiple forms of right buudie branch . The His bundle deflection could not be tachycardia may be present in any given patient with only recorded after right bundle branch ablation in Patient 6 . The one configuration representing bundle branch reentrant HV interval remained unchanged after ablation in all other tachycardia . In Patient 3 the baseline ECG showed a com- patientsprolongation except Patient 3, who showed marked HV plete left bundle branch block pattern (Fig . 3). Bundle (from 80 to 170 ms) but who already had a permanent branch reentrant tachycardia had a left bundle branch block pacemaker . AH and HV intervals and QRS duration were configuration and an inferior axis at a cycle length of 330 ms . statistically unchanged after ablation . Infranodal block was Radiofrequency ablation resulted in complete right bundle not present during either atrial overdrive pacing or during branch block after which bundle branch reentrant taehyear- programmed atrial extrastimuli dia was no longer inducible. However, this patient also had . Repeated attempts at induc- tion after ablation (and during the same procedure) were ventricular tachycardia of myocardial origin with a different configuration . Right bundle branch ablation succeeded in unsuccessful in initiating bundle branch reentrant tachycar- control of the tachycardia with an inferior axis (bundle dia in all patients . branch reentrant tachycardia) but not that with a superior All patients underwent an additional repeat electrophys- axis (myocardial ventricular tachycardia) . The latter ar- iologic study either before discharge or at 6-month follow- rhythmia was never documented clinically and was not up. Three patients (Patients 3, 5 and 7) still had inducible treated . sustained monomorphic ventricular tachycardia originating Patient 6 had a long history of recurrent ventricular from ventricular myocardium. In Patient 3 ventricular tachy- tachycardia treated elsewhere with amiodarone . He under- cardia was slow (430 ms cycle length) and not associated went AV junction ablation at our institution for symptomatic with hemodynamic compromise . He was discharged without atrial fibrillation (Fig, 4A) followed by pacemaker implanta- antiarrhythmic therapy and never had spontaneous recur- tion . He was referred back for possible recurrence of AV rence . The "myocardial" ventricular tachycardia of Patient conduction with presumed atria) flutter and, at electrophys- 5 recurred spontaneously and is currently controlled with iologic study, was found to have complete AV block and amiodarone therapy . Patient 7 had an inducible, rapid, bundle branch reentrant tachycardia (Fig . 4R). This case hemodynamically unstable myocardial ventricular tachycar- demonstrates that bundle branch reentrant tachycardia may dia at restudy and underwent implantation of an automatic resemble wide complex supraventricular (such cardioverter-defibrillator, as atria) flutter w''ah aberrant conduction) and can occur even Follow-up. At a mean follow,up period of 12 ± 3 months in the presence of complete AV block . (range 6 to 29), complete right bundle branch block persisted Catheter ablation of the right bundle . One to three appli- in all patients and there were ro recurrences of bundle cations of radiofrequency energy (15 to 20 W for up to 60 s) branch reentrant tachycardia . Patient I died of end-stage

tACt. Vol . IN. No. 7 C1711EN ET AL. ue,emn~r te91 :1m7as 1771 R .AD10FRF 1LFYCY An-110N r io lit SULE aa,ACH REENTRANTT;CHYCARn1A

figure 4. Patient 6 . A, the baseline i2-lead EC( ; Alnal fibrillation is present (before a^invcntricublr comp)-,,, IAVI junction ablation) with a left bundle branch block pattern . B, a regular aide oompLx muhycardla al a mte of 150 bcatsimin is pr°Sent slier AV junction ablation with a configuration and axis similar to those observed on the baseline ECU . thin pdient was tlmuilht to have a recurrence of AV conduction with atriai flutter and 2 .1 AV - ,arc-lion. At eloctrophysiologic study . comnlelc AV block was present and bundle branch reentrant rachye-rdia was identified .

congestive failure arid uremia 29 months after the Uisenssinn ablation procedure . Patient 3 died of an unrelated cause Long-term efiicecy of radiofrequenry ablation in bundle (sepsis post-herniorrhaphy) . Patient 4 returned for treatment branch reentrant tachycardia . In 1589 Langberg et al. L-1) at of atrial fibrillation with aberrant conduction that was con- our institution reported the first successful bundle branch trullcd with propatenone. Two patients already had a pace- reentrant tochycatdia Oblation. with use of r,,diofrquency maker before right bundle branch dbiattoa but none of the energy (Patient If. This patient lived for 29 months after the others required pacemaker placental procedure without arrhythmia recurrence, then died of un-

Table 3. .4[rroventricular Cacdunlon tdore :,nd At- Ablation iu Seven Cases

C rises Alter Ablution A No NH lent EIV nail QRS,mr . AHro,t HV Ira,, QRS lmel

t or 1*1 'in so ion I10 13 1411 ns e11 IN7 Ipl Nd 101 I On 1711 140 m nn 111) W NO 7o n: '.m al 67 rn a.l lµt elal 7 as nn tt nn Mean ~ SE IN c 19 79 e 2 141 : 11 10" 16 93 r 15 179 _ 17 'Atria) thrillalion pe ,- ; -m,, rauso &d : nhcm was ru.,igniflcanl dlkkrmces hwwean outlast a' h.neline .md aterahiainn,

1772 COHEN CT AL. (ACC V.I. 18 . No 7 RADIOFRCQUENCY ABLATION FOR BUNDLE BRANCH REENTRANT TACHYCARDIA December 1991:1767-73

related causes. Subsequently . six additional patients were ertheless, our overall incidence of bundle branch reentrant identified as having this form of tachycardia and were tachycardia is similar to the reported incidence of this entity successfully treated with this approach . Each patient was (1) . highly symptomatic (syncope or aborted sudden death) . Significance of left bundle branch block on a baseline ECG . although only two had 12-lead ECG documentation of spon- Three of our seven patients had a baseline 12-lead ECG taneous episodes with a configuration Identical to that of consistent with a complete left bundle branch block pattern . bundle branch reentrant tachycardia induced in the electro- This pattern is obviously due to a conduction delay rather physiology laboratory (Patients 2 and 61 . We can only infer than to complete block in the left bundle because induced that bundle branch reentrant tachycardia was the clinical block in the right bundle forced exclusive conduction over arrhythmia in the other five patients because I) induction of the left bundle . Thus, the presence of a complete left bundle handle branch reentrant tachycardia reliably replicated the branch block pattern on baseline ECG or even complete AV clinical presentation and 2) after right bundle branch ablation block (Patient 6) does not exclude a bundle branch reentrant there was no recurrence of these symptoms . To our knowl- mechanism . Three patients had both inducible sustained edge . this is the first study to demonstrate long-term efficacy monomorphic ventricular tachycardia of a bundle branch of radiofrequency ablation in the treatment of bundle branch and a myocardial reentrant mechanism. This emphasizes the reentrant tachycardia . In seven patients no complications or importance of a thorough investigation of a bundle branch arrhythmia recurrences were observed (immediate or long- reentrant mechanism even if other etiologies are identified term) over 83 months combined follow-up : two patients died (and vice versa) . In addition, bundle branch reentrant tachy- of unrelated causes . cardia mimicked supraventricular tachycardia with aberra- Previous studies. Previous studies demonstrated that di- tion in one patient . rect current catheter ablation may successfully interrupt the Conclusions. The possibility of bundle branch reentrant macrorcentrant circuit and cure patients with bundle branch tachycardia must be carefully evaluated in all patients with reentrant tachycardia . Successful direct current ablation has known or suspected ventricular tachycardia . All patients in been reported (2-4) in 12 patients with bundle branch our study presented with either syncope or aborted sudden reentrant tachycardia (and at least 8 of these received a death. Radiofrequency ablation of the right bundle branch prophylactic permanent pacemaker) . Radiofrequency en- appears to be a safe and effective treatment modality . We ergy appears preferable to direct current for ablation be- found a high incidence (three of seven patients [43%]), of cause it can be delivered without general anesthesia or coexisting ventricular tachycardia of myocardial origin, barotrauma and produces more shallow and more uniform which required active therapy in two patients . Despite the and smaller zones of myocardial damage (9-11) . It is con- presence of an intraventricular conduction defect or left ceivable that radiofrequency ablation may be more likely bundle branch pattern, there was no progression to complete than other procedures to interrupt the right bundle branch AV block during follow-up in the five patients without a alone without more diffuse effects on the specialized ventric- permanent pacemaker. One patient did show marked pro- ular conduction system . Only one of our patients showed longation of the HV interval after ablation ; therefore, these significant prolongation of ittfranodal conduction after abla- patients must be carefully observed with regard to develop- tion. Five patients who showed no significant changes in the ment of progressive disease of the specialized ventricular HV interval are currently being followed up without a conduction system. We conclude that radiofrequency abla- pacemaker. tion is a safe and effective treatment for bundle branch The incidence of bundle branch reentrant tachycardia in reentrant tachycardia and probably the procedure of choice our patients with ventricular tachycardia is similar to that for these highly symptomatic patients . reported by Caceres et al. (1) . Four of our seven patients with this arrhythmia had coronary artery disease and three had cardiomyopathy. Although our incidence of bundle References branch reentrant tachycardia (16.6%) for patients with car- I . Caceres J. Jazayeri M, McKinnie l. et aL sustained bundle branch diomyopathy was lower than that previously reported (36%) reentry mechanism of clinical tachycardia. Circulation 1989 :79:256- (1), it was nevertheless significantly greater than in those 70 . with coronary artery disease (4 .5%). 2 . Tchou t', Jazayeri M . Denker 5, Douglas J,.., Ca J . Aklam M. The pause protocol . In the previously reported largest Trnscatheter electrical ablation of right bundle branch : a method of treating macroreentrant ventricular tachycardia auribmed to bundle series of bundle branch reentrant tachycardia (1), a pause branch reentry. Circulation 1988:79:246-57 . protocol was used to induce the tachycardia . In the present 3 . Tampa) P. Kokorian G. Atallah G, el al . Bundle branch reentrant series the tachycardia was inducible in all patients with use tachycardia heated by electrical ablation of the right bundle branch . J Am Call Cardmel 1986;7:1404-9 . of a standard protocol . It was appreciated, however, that the +. . Volkmann H . Kuhnen H, Dannberg G . Heinke M . Bundle blanch tachycardia could be induced more easily with use of a pause reentrant tachycardia seated by tmnsvenous catheter oblation of the right protocol in Patient 7 . We cannot exclude the possibility that bundle brunch . PACE 1989;12:258-61 . 5 . Lungberg 13, Desai 1, Dania N. Scheinman MM . Treatment of mac' this protocol might have improved the sensitivity of diagnos- eureentrant vemricular tachycardia with rdiafreyucncy ablalion of the ing bundle branch reentrant tachycardia in our study, nev- right bundle branch. Am J Cardiol 1989 :63 :1010-3.

JACC Vol . 18. No.7 CO . El ET IL . 1773 December 1991 :1767-73 RADIOFREQCENC9 O BI .A I l10\ FOR Bt P'DI E BR.OVCH REENTRANTTACHYCARDIA

fi. Denker 5, Lehmann M . Mahmud R, Gilhon C . Akhlar M . Eacilo enm of henec}eamic OR- of c:aheler doVoorod ablation 0000930, in th0 ventnculartachyeardu induction with thrum changes In vcmdcular cycle oode No, J Cnrdlo] 1090 06 :373-7. lenglh. Am 1 Cardiol 1981.5}500-15. 7. Touhoul P, Kirk- G. Alzllah G. !bleu : P Bond[, branch reemrt- e to Haucr RNW . Slruka W. Borsl C . Roblno d0 Metine EO . Electrical possible mechunirm of vm.tricular lachycurdie. Circulation 19d3 ., 674- cohela0'Mn"'n in the left crib 9hl ronhieulm cell in ~!oRS slcliun 80 . b01-an Jalii-ObRJ 000090 cod hc :o7mhulRic deny- J A.v CA Cardiol 19096637-13 8. Akhtar M. Dammo AN. Butsford WP. R,,kin 1N . Ocunkclu JB . Var0a, G . Demonstration of reentry in HiS-Purkinje sy,tem is man . Cimulal on rx 11. Evmr G' f. Vohemmn0 MM . C3lhete7 ablation of mrdoc 1971 .50 :1150 . rrh,0noa . In. 0 Rourke RA . od. Cnmnt Problems in 0,1, loev . Vol . 9 . Kempf FC. Falcon RA . loan RV, Jaephsnn ME .,atom!, and II Chicano Trio Book hledicdl . 1909-1'9 90 .