CONTRIBUTION. Atrial fibrillation and flutter with left bundle branch block aberration referred as ventricular tachycardia

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1 CONTRIBUTION 9H Atral fbrllaton and flutter wth left bundle branch block aberraton referred as ventrcular tachycarda RICHARD G. TROHMAN, MD; KENNETH M. KESSLER, MD; DEBORAH WILLIAMS, MD; AND JAMES D. MALONEY, MD Fve patents were referred for electrophysologc evaluaton of nonsustaned or sustaned ventrcular tachycarda. In each patent, the clncal rhythm dsturbance was reproduced and dentfed as atral fbrllaton or flutter wth left bundle branch block aberrancy. All fve patents demonstrated enhanced or accelerated atroventrcular conducton through the normal atroventrcular nodal-hs Purknje pathway. Ths rapd conducton created an electrophysologc substrate sutable to the preferental development of ths less common form of aberraton. Four of fve patents responded well (ventrcular rate control or reverson to snus rhythm) to verapaml therapy. Electrocardographc crtera for dfferentatng supraventrcular tachycarda wth aberraton from ventrcular tachycarda exst. Nevertheless, msdagnoss of wde complex tachycarda remans common. Electrophysologc testng plays an mportant role n correctly dentfyng these rhythms, assessng long-term prognoss, and choosng effectve therapy. INDEX TERMS: LEFT BUNDLE BRANCH BLOCK ABERRANCY; ATRIAL FIBRILLATION AND FLUTTER 0 CLEVE CLIN ] MED 99; 58: ELECTROCARDIOGRAPHIC CRITERIA EXIST to ad n the dfferentaton of aberrantly conducted QRS complexes from complexes of ventrcular orgn durng atral fbrllaton.,2 Addtonal electrocardographc crtera ad n dfferentatng ventrcular tachycarda from supraventrcular tachycarda wth aberraton. 3 ' 5 Aberraton durng atral fbrllaton or flutter s bengn, and t has a rght bundle branch block (RBBB) confguraton n 80% of cases. Ventrcular tachycarda s a potentally lethal arrhythma requrng dfferent and often much From the Department of Cardology, The Cleveland Clnc more aggressve treatment. Hence, the dstncton be- Foundaton (R.G.T., D.W., J.D.M.), and the Mam VA Medcal Center (K.M.K.). Address reprnt requests to R.G.T., Electrophysology and Pacng Secton, Department of Cardology, F5, The Cleveland Clnc Foundaton, One Clnc Center, 9500 Eucld Avenue, Cleveland, Oho tween these rhythm dsturbances s of obvous clncal mportance. Our report descrbes the results of electrophysologc testng n fve patents referred for evaluaton of ventrcular tachycarda. In each nstance, the clncal rhythm dsturbance was proven to be supraventrcular n orgn e, atral fbrllaton or flutter wth left bundle branch block (LBBB) aberraton. METHODS Patent characterstcs The study group conssted of fve adult patents (four men, one woman), ages 24 to 62, referred for evaluaton of ventrcular tachycarda (Table I). Each had runs of wde QRS complex tachycarda of LBBBtype confguraton, rangng n duraton from fve beats to sustaned (greater than 30 seconds), and documented by surface electrocardogram, ambulatory montorng, or contnuous bedsde montorng (Fgure JULY-AUGUST 99 CLEVELAND CLINIC JOURNAL OF MEDICINE 325

2 TABLE PATIENT CHARACTERISTICS Patent Age/sex Baselne electrocardogram Echocardgraphy Etology of underlyng heart dsease Reason for referral 24,F Nonspecfc ST changes Slght bventrcular dlataton Unknown NSVT 2 50,M Normal snus rhythm, left axs devaton, nonspecfc ST changes Left atral enlargement, dffuse left ventrcular hypokness Ethanol 3 62,M Left atral enlargement Left ventrcular hypertrophy Ethanol, hypertenson VT 4 62,M Old nferor myocardal nfarcton, nonspecfc ST changes 5 62,M Atral fbrllaton, old anteroseptal myocardal nfarcton Techncally suboptmal normal ejecton fracton Dlated left ventrcle wth decreased ejecton fracton Coronary artery dsease Coronary artery dsease VT NSVT NSVT NSVT = nonsustaned ventrcular tachycarda. VT = sustaned ventrcular tachycarda. raphy. Left ventrcular hypertrophy was present by both electrocardographc and echocardographc crtera n the latter patent. Baselne electrocardography demonstrated narrow QRS complexes n all fve patents. Snus rhythm was present n four patents; one had chronc atral fbrllaton. : H4- I } I j I h ' ' l v ~ [ (T ^ yr E S E E E E Ï Î Ï ± E : - 44Ü: :_ ± D Éf# Fgure. Rhythm strp demonstrates sustaned left bundle branch block aberraton (Patent 3). Electrophysologc testng revealed atral flutter wth a rapd ventrcular response and left bundle branch block aberrancy (surface electrocardographc leads I, II, and V). Electrophysologc testng Electrophysologc studes were performed n the sedated (oral dazepam or ntramuscular pentobarbtal sodum [Nembutal]) postabsorptve state, wth the patent takng no cardoactve medcatons. Three quadrpolar catheters were nserted percutaneously and postoned to record hgh rght atral, Hs bundle, and rght ventrcular apcal electrograms. In two patents, a fourth quadrpolar catheter was nserted percutaneously nto the coronary snus. Incremental pacng and programmed atral stmulaton were performed n the four patents wth normal snus rhythm. Incremental pacng and up to three extra-stmul were delvered to the rght ventrcular apex and outflow tract. Rapd rght atral pacng was used to nduce atral fbrllaton or flutter. ). One patent had bventrcular enlargement of uncertan etology. The left ventrcular ejecton fracton was wthn normal lmts. Two patents had coronary artery dsease wth documented myocardal nfarcton, one of whom had ventrcular fbrllaton at the tme of acute nfarcton. Two patents had hstores of ethanol abuse, one wth markedly reduced left ventrcular functon and a hstory of congestve heart falure, the other wth normal left ventrcular functon by echocardog- RESULTS Replcaton of clncal rhythm dsturbance Ventrcular tachycarda was not nducble n any of the fve patents. None of the patents demonstrated ether atroventrcular (AV) nodal reentry or crcus movement tachycarda nvolvng a manfest or concealed accessory pathway. Atral fbrllaton or flutter wth reproducton of the clncal LBBB morphology 326 CLEVELAND CLINIC JOURNAL OF MEDICINE VOLUME 58 NUMBER 4

3 TABLE 2 ELECTROPHYSIOLOGIC DATA, RESPONSES TO PHARMACOLOGIC INTERVENTION Patent Baselne AH Change n AH Shortest CL : AV conducton Arrhythma Response to verapaml Atral flutter, ventrcular rate up to 300, LBBB aberraton 20 mg td orally decreased ventrcular rate to * Atral fbrllaton, ventrcular rate 200, LBBB aberraton Atral flutter, ventrcular rate 80, LBBB aberraton Atral fbrllaton and flutter, ventrcular rate 50-90, LBBB aberraton 0 mg IV decreased ventrcular rate to 30 No change wth oral or IV 5 mg IV produced prompt reverson to snus rhythm - t - t - t Atral fbrllaton, ventrcular rate 200, LBBB aberraton 0 mg IV decreased ventrcular rate to 80 Baselne AH = atro-hs nterval n msec, measured n the Hs bundle electrogram. Change n AH = change between AH measured durng snus rhythm and AH measured durng the shortest cycle achevng : AV conducton. CL = cycle length. LBBB = left bundle branch block. * = rght atral pacng at shorter cycle lengths not attempted because of tachycarda nducton, t = conducton nterval not measured because baselne rhythm was atral fbrllaton. was nducble (or present at baselne) n all fve patents (Table 2, Fgures 2 and 3). Patterns of AV conducton There was no evdence of preexctaton n any of these patents. The crucal electrophysologc lnk between them was rapd conducton va the normal pathway. All patents acheved ventrcular rates greater than or equal to 200 beats per mnute va conducton through the AV nodal-hs Purknje system durng rapd atral pacng or tachycarda (Fgure 4). Coexstence of RBBB aberraton Clncal and electrocardographc observaton has suggested that LBBB aberraton usually coexsts wth RBBB aberraton. RBBB-type beats were observed clncally (sngle beats only) and electrophysologcally n only two of our fve patents. Response to therapeutc nterventon Verapaml has been suggested as a drug of choce for prompt slowng of rapd ventrcular rates that occur n patents wth rapd AV nodal conducton. 6 ' 7 Dramatc mprovement occurred after ntravenous or oral verapaml therapy n four of our fve patents. The ffth patent dd not respond to ntravenous (0 mg) or oral (80 mg four tmes daly) verapaml. DISCUSSION RBBB aberrancy s four tmes more common than LBBB. Thus, runs of aberraton wth LBBB confguraton are more often msnterpreted as paroxysmal ventrcular tachycarda. Electrophysologc testng dfferentates LBBB aberraton from ventrcular tachycarda. Ths requres a stable, sharp Hs bundle recordng, and careful determnaton of the HV nterval durng snus rhythm, and/or narrow complex tachycarda. The Hs bundle recordng (Fgure 2) s comprsed of two contguous segments: The AH nterval measures conducton tme from low septal rght atrum to Hs bundle; t prmarly reflects conducton velocty through the AV node. The HV nterval s measured from the onset of the Hs bundle deflecton to the earlest ventrcular depolarzaton; t reflects nfranodal conducton velocty. Supraventrcular ectopc beats wll have HV ntervals equal to or exceedng (nfranodal conducton delay) the HV nterval measured durng snus rhythm. Ventrcular ectopc beats do not requre pror depolarzaton of the Hs- Purknje system to propagate. HV ntervals wll be absent or less than the HV measured durng snus rhythm. Wde complex tachycardas wth HV ntervals less than those recorded durng snus rhythm or narrow complex tachycarda are ventrcular n orgn. Wde JULY AUGUST 99 CLEVELAND CLINIC JOURNAL OF MEDICINE 327

4 HBE Hf- HBE A H V j f t - t f W - ^ y ^ j ^ w ^ u. f I l HBE 'HBE RV RV v ' Y W V W V W V W W W HBE^ Y^^^T" ^ HBE^ llllljjjiij.ii.ll.llljlll.ljiulljjjjj IJlLllJllUllll. Fgure 2. A) Durng rght atral pacng (beat shown on the left), left bundle branch block aberraton wth an HV nterval measured to be 75 mllseconds was demonstrated n Patent 2. The normal snus beat (strp s not contnuous) has an HV nterval of 50 mllseconds. B) Electrophysologc testng reveaed sustaned atra fbrllaton wth dentcal left bundle branch aberraton nduced by rght atral pacng at a cycle length of 350 mllseconds. Average ventrcular rate was 200 beats per mnute. The HV nterval agan measured 75 mllseconds. (I, II, and VI surface electrocardographc leads, II, and VI. RA = rght atral electrogram. HBE = Hs bundle electrogram. HV nterval measured from the Hs bundle deflecton to the earlest ventrcular actvty [surface electrocardogram or ntracardac recordngs].) complex tachycardas wth HV ntervals equal to or greater than those durng snus rhythm or narrow complex tachycarda are supraventrcular n orgn. Mechansms of aberraton Enhanced AV nodal conducton s defned as follows: AH ntervals durng snus rhythm of less than or equal to 60 ms; : conducton between the atrum and Hs bundle at rght atral pacng cycle lengths of less LL.J Fgure 3. Atral flutter wth 2: atroventrcular block and left bundle branch block aberraton was nduced n Patent 4, who had been referred for runs of nonsustaned ventrcular tachycarda. (I, II, and V= surface electrocardographc leads. RA = rght atral electrogram. HBE = Hs bundle electrogram, RV = rght ventrcular electrogram.) than 300 ms; and less than 00 ms dfference between the AH nterval measured durng snus rhythm and rght atral pacng at 300 ms was present n two patents. 8 These crtera could not be assessed n one patent wth chronc atral fbrllaton. The other two patents were felt to have "accelerated" AV conducton. 9 Jackman et al 0 have shown that nether the baselne AH nterval nor the change n AH nterval wth rght atral pacng s partcularly useful n defnng a subgroup of patents wth rapd AV conducton. They found that the ventrcular rate recorded durng atral fbrllaton correlates hghly wth the shortest : cycle length durng rght atral pacng. Thus no mportant dstncton between our patents' conducton patterns was present. Ths rapd conducton pattern created the mleu essental to the preferental development of LBBB aberrancy. Preferental development of LBBB aberrancy s best explaned by the response of the bundle branches to rapd ventrcular rates and the clncal features of tachycarda-dependent aberraton. At slow heart rates, the refractory perod of the rght bundle branch usually exceeds that of the left bundle branch. 2 At faster rates, the refractory 328 CLEVELAND CLINIC JOURNAL OF MEDICINE VOLUME 58 NUMBER 4

5 ATRIAL FIBRILLATION TROHMAN AND ASSOCIATES perod of the left bundle branch may exceed that of the rght bundle branch. ' 2 In our patents, fast ventrcular rates occurred n assocaton wth rapd AV nodal conducton. Tachycarda-dependent aberraton may occur at crtcal heart rates. Ths phase III aberraton exhbts a predomnance of LBBB morphology. Development of phase III aberraton s ndependent of the mmedately precedng cycle length and occasonally appears wth no, or only a slght, change n cycle length. These features dffer from the usual R B B B aberrancy related to the Ashman phenomenon. Rate-dependent aberrancy generally appears at relatvely slow heart rates, but may make ts ntal appearance at very rapd rates and s seen almost exclusvely n patents wth heart dsease.3 Our fve patents had structural cardac abnormaltes. Rate-dependent aberrancy s not a common mechansm of wde Q R S tachycarda. In the presence of structural heart dsease, wde complex tachycarda s almost always ventrcular n orgn.5 In atral fbrllaton and flutter, several features contrbute to persstent aberrancy at R-R ntervals longer than the nterval ntatng aberrancy. The most mportant mechansm s concealed antegrade penetraton of the blocked bundle branch. Ths results n true bundle branch depolarzatons that are shorter than manfest R-R ntervals. Less mportant roles are played by concealed transseptal actvaton (wth block of conducton n the contralateral bundle) and tme-dependent aberrancy.3 Electrocardographc correlates and lmtatons Electrocardographc crtera have been descrbed to dfferentate ventrcular tachycarda from supraventrcular tachycarda wth aberraton.3,4 Kndwall et al4 have descrbed four crtera suggestng a ventrcular orgn n L B B B tachycarda: ) an R wave n V or V2 greater than 30 ms n duraton; 2) the presence of any Q wave n V6; 3) notchng on the S wave downstroke n V or V 2 ; 4) greater than 60 ms from the onset of the Q R S to the nadr of the S wave n V or V2. Most ventrcular tachycardas have rates between 30 and 70 beats per mnute and Q R S duratons exceedng 0.4 seconds (0.6 sec for L B B B morphology ventrcular tachycarda). Four of our fve patents had ventrcular rates exceedng 70 beats per mnute. Four patents had Q R S wdths durng tachycarda of less than 0.4 seconds. Use of addtonal Q R S characterstcs was lmted by the fact that three of our patents had nonsustaned arrhythmas. When a 2lead electrocardogram recorded durng tachycarda JULY AUGUST 99 PR NN t" F r H - I { ' Jt ^ * J. V Nñ 4 \ 4 ; f f ' kjo 'V N IH v 4 - H ' f ' Fgure 4. Atral pacng at a cycle length of mllseconds resultng n : atroventrcular conducton and left bundle branch block aberraton (Patent ). was avalable, Q R S characterstcs supported a supraventrcular orgn for the tachycardas (Fgure, lead V]). One patent had runs of narrow complex rregularly rregular tachycarda precedng wde complex beats. Although some electrocardographc crtera suggested supraventrcular orgns for these tachycardas, confrmaton requred ntracardac electrophysologc studes. Prognostc and therapeutc mplcatons Sustaned ventrcular tachycarda s a lfe-threatenng rhythm. Aggressve therapy guded by electrophysologc testng decreases mortalty. Pharmacotherapy s often nsuffcent to control sustaned ventrcular tachycarda and surgcal nterventon may be requred (subendocardal resecton or use of an mplantable cardoverter defbrllator). Nonsustaned ventrcular tachycarda s a potentally lethal arrhythma and s assocated wth an ncreased rsk of sudden cardac death n patents wth underlyng heart dsease.4 Approprate management of asymptomatc nonsustaned ventrcular tachycarda remans uncertan. Cardac Arrhythma Suppreson Tral data5 provde evdence that pharmacotherapy wth the Type IC drugs encande and flecande ncreases mortalty. The hemodynamc effects of atral tachyarrhythmas correlate wth ventrcular rate and myocardal reserve. In general, paroxysmal atral fbrllaton and flutter are not assocated wth sudden cardac death. Rapd ventrcular rates occurrng abruptly n patents wth serous cardac dsease may be devastatng. However, when ventrcular rates are well-controlled, these rhythm dsturbances are compatble wth years of uneventful survval, and contrbute lttle to the morbdty and mortalty of heart dsease.6 Therapy of atral flutter and fbrllaton s ntally CLEVELAND CLINIC JOURNAL OF MEDICINE 329

6 drected at AV nodal blockade (controllng ventrcular rate). Dgtals, beta blockers, and verapaml (or combnatons of these agents) usually acheve AV nodal blockade. The restoraton and mantenance of snus rhythm correlates nversely wth the duraton of the arrhythma and left atral sze. Type IA antarrhythmcs are most frequently employed to control the atral rhythm dsturbance. Flecande may also be used wth effcacy smlar to qundne. 7 Pharmacotherapy s well-defned and effectve for atral fbrllaton and flutter. Antarrhythmc drug management of ventrcular tachycarda s ll-defned, frequently neffectve, and fraught wth the rsk of proarrhythma. In our patents, response to pharmacologc nterventon was greatly nfluenced by the supraventrcular orgn of the arrhythmas. Verapaml resulted n mprovement n four patents and had no effect on one patent. Ths result s n contrast to drug therapy ventrcular tachycarda, where seral drug testng may fal to acheve arrhythma control and ntravenous verapaml may produce hemodynamc collapse. 8,9 REFERENCES. Cohen SI, Lau SH, Haft JI, Damato AN. Expermental producton of aberrant ventrcular conducton n man. Crculaton 967; 36: Sandler IA, Marrott HJL. The dfferental morphology of anomalous complexes of RBBB-type n lead VI: Ventrcular ectopy versus aberraton. Crculaton 965; 3: Wellens HJJ, Bar FWHM, Le KI. The value of the electrocardogram n the dfferental dagnoss of a tachycarda wth a wdened QRS complex. Am J Med 978; 64: Kndwall KE, Brown J, Josephson ME. Electrocardographc crtera for ventrcular tachycarda n wde complex left bundle branch block morphology tachycardas. Am J Cardol 988; 6: Akhtar M, Shenasa M, Jazayer M, Caceres J, Tchou PJ. Wde QRS complex tachycarda Reapprasal of a common clncal problem. Ann Intern Med 988; 09: Castellanos A, Zaman L, Lucer RM, Myerburg RJ. Arrhythmas n patents wth short PR ntervals and narrow QRS complexes. In: Josephson ME, Wellen HJJ, eds. Tachycardas: Mechansms, dagnoss, treatment. Phladelpha: Lea and Febger; 984: Bgger JT. Perspectves on the current treatment of cardac arrhythmas. Am J Cardol 984; 54:2B-7B. 8. Stafford WJ, Trohman RG, Blsker M, Zaman L, Castellanos A, Myerburg RJ. Cardac arrest n an adolescent wth atral fbrllaton and hypertrophc cardomyopathy. J Am Coll Cardol 986; 7: Holmes DR, Hartzler GO, Meredeth J. The clncal and electrophysologc characterstcs of patents wth accelerated atroventrcular nodal conducton. Mayo Cln Proc 982; 57: Jackman WM, Prystowsky EN, Naccarell GV, et al. Réévaluaton of enhanced atroventrcular nodal conducton: Evdence to suggest a contnuum of normal atroventrcular nodal physology. Crculaton 83; 67: Myerburg RJ, Stewart JW, Hoffman BF. Electrophysologc propertes of the canne perpheral A-V conductng system. Crc Res 970; 26: Chlson DA, Zpes DP, Heger JJ, Browne KF, Prystowsky EN. Functonal bundle branch block: Dscordant responses of the rght and left bundle branches to changes n heart rate. Am J Cardol 984; 54: Fsch C, Zpes DP, McHenry PL. Rate dependent aberrancy. Crculaton 973; 38: Bgger JT. Identfcaton of patents at hgh rsks for sudden cardac death. Am J Cardol 984; 54:3D-8D. 5. The Cardac Arrhythma Suppresson Tral (CAST) Investgators. Prelmnary Report: Effect of encande and flecande on mortalty n a randomzed tral of arrhythma suppresson after myocardal nfarcton. New Engl J Med 989; 32: Bgger JT. Mechansms and dagnoss of arrhythmas. In: Braunwald E, ed. Heart Dsease. st ed. Phladelpha: WB Saunders. 980: Borgeat A, Goy JJ, Maendly R, Kaufmann U, Grbc M, Sgwart U. Flecande versus qundne for converson of atral fbrllaton to snus rhythm. Am J Cardol 986; 58: Dancy M, Camm AJ, Ward D. Msdagnoss of chronc recurrent ventrcular tachycarda. Lancet 985; : Buxton AE, Marchlnsk FE, Doherty JU, Flores B, Josephson ME. Hazards of ntravenous verapaml for sustaned ventrcular tachycarda. AmJ Cardol 957; 59: CLEVELAND CLINIC JOURNAL OF MEDICINE VOLUME 58 NUMBER 4