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Journal of Electrocardiology 44 (2011) 289–295www.jecgonline.com

Electrocardiographic characteristics in right ventricular vs biventricularpacing in patients with paced right bundle-branch block QRS pattern☆

Marwan Refaat, MD,a Moussa Mansour, MD,b Jagmeet P. Singh, MD, PhD,b

Jeremy Ruskin, MD,b E. Kevin Heist, MD, PhDb,⁎aCardiac Electrophysiology Service, University of California San Francisco Medical Center, San Francisco, California, USA

bCardiac Arrhythmia Service, Massachusetts General Hospital, Harvard Medical School, Boston, Massachusetts, USA

Received 15 January 2010

Abstract Background: A paced right bundle-branch block (RBBB) QRS morphology is present in most

Abbreviations: ECventricle; BiV, bivenbiventricular pacing; R

☆ Presented as anAmerican College of

⁎ CorrespondingUnit, Massachusetts GMA 02114, USA.

E-mail address: k

0022-0736/$ – see frodoi:10.1016/j.jelectroc

patients with biventricular pacing (BiVP) but is also present in some patients with right ventricularpacing (RVP). The aim of this study was to determine if there are electrocardiographic characteristicsthat distinguish BiVP from RVP in patients with a paced RBBB QRS pattern.Methods: Twelve-lead–paced electrocardiograms (ECGs) were analyzed from 356 consecutivepatients (302 RVP and 54 BiVP). Further analyses were performed on those ECGs with a pacedRBBB morphology, which included QRS pattern, axis, amplitude, and precordial transition. Chestradiography and coronary sinus venography were used to determine the location of the pacing leads.Results: Fifty (16.6%) of 302 RVP ECGs and 50 (92.6%) of 54 BiVP ECGs had RBBB-pacedmorphology, respectively. Electrocardiographic characteristics identified in this studywith a paced RBBBQRSmorphology that are associated with RVP but not with BiVP (P b .05) include positive concordancein the precordial leads, qR configuration in lead V1, and a late QRS transition beyond lead V3.Biventricular pacing had shorter mean–paced QRS duration than did RVP and was associated withright superior quadrant mean frontal QRS axis (P b .05). Right ventricular pacing was associatedwith a mean frontal QRS axis in the left superior quadrant (P b .05). Regarding left ventricular (LV)pacing site, a late precordial transition (especially beyond lead V2) was significantly associated witha more posterior LV lead location (P b .05).Conclusions: Even among patients with a paced RBBB QRS pattern, the 12-lead ECG can helpdistinguish RVP from BiVP and determine LV lead location during BiVP. This information may beuseful in evaluating nonresponse to BiVP resulting either from LV noncapture (with consequentRVP) or from suboptimal LV lead location during BiVP.© 2011 Elsevier Inc. All rights reserved.

Keywords: Electrocardiography; Cardiac resynchronization therapy; Pacemaker

Introduction

Biventricular pacing (BiVP) is an established therapy forpatients with systolic heart failure refractory to medicaltherapy and intraventricular conduction delay.1-4 Patients

G, electrocardiogram; LV, left ventricle; RV, righttricular; RBBB, right bundle-branch block; BiVP,VP, right ventricular pacing.abstract at the 58th Annual Scientific Sessions of theCardiology, March 30, 2009, Orlando, FLA.author. Cardiac Arrhythmia Service and Cardiaceneral Hospital, 55 Fruit Street, Gray 109, Boston,

heist@partners.org

nt matter © 2011 Elsevier Inc. All rights reserved.ard.2010.08.003

typically undergo implantation of a cardiac resynchroniza-tion device along with 3 pacing leads, as follows: a standardright atrial lead, a standard right ventricular (RV) lead, and aspecialized left ventricular (LV) lead, which is placed into adistal cardiac vein by way of the coronary sinus through aguiding catheter. The presence, diameter, angulation, andtortuosity of coronary veins as visualized by retrogradevenography determine their acceptability for the placementof a lead in a predetermined location.5,6

The paced 12-lead electrocardiogram (ECG) is a simple,inexpensive, and valuable tool in the assessment of patientswith pacemakers. The data on ECG patterns in BiVP are stilllimited. There are relatively few publications that assessed12-lead ECG characteristics comparing RV pacing (RVP) vs

Fig. 1. Position of the LV lead by the lateral view of the chest x-ray: anterior,between 12o'clock and1o'clock; anterolateral, between 1o'clock and2o'clock;lateral, between 2 o'clock and 4 o'clock; posterolateral between 4 o'clockand 5 o'clock; and posterior between 5 o'clock and 6 o'clock.

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BiVP.7-12 The small number of patients and paucity ofvariables studied limit the available data. Furthermore,previous studies reported that during BiV stimulation, theQRS is often positive in lead V1, commonly termed a rightbundle-branch block (RBBB) pattern of depolarization. This“RBBB pattern” of depolarization has also been reported in8% to 10% of patients with standard pacemakers pacing theRV apex.13 No prior study has directly compared the ECGcharacteristics that distinguish BiVP from RVP in patientswith a paced RBBB QRS pattern.

The aims of this study are to describe the 12-lead–pacedECG patterns in patients undergoing RVP and BiVPproducing a paced RBBB pattern and to determine if thereare ECG characteristics that distinguish BiVP from RVP inthese patients. This study aims as well to assess whether LVlead location impacts the ECG pattern.

Table 1Prevalence of ECG-paced morphology

Paced morphology RVP (n = 302) BiVP (n = 54)

RBBB 50 (16.6%) 50 (92.6%)LBBB 252 (83.4%) 4 (7.4%)

Methods

Study population

This study involved all patients who underwent theimplantation of a pacemaker or implantable cardioverter-defibrillator (ICD) at Massachusetts General Hospitalbetween January 2005 and January 2007. Three hundredfifty-six patients were enrolled in this study (302 patients hadRVP and 54 patients had BiVP). The institutional reviewboard of the Massachusetts General Hospital approved thisstudy protocol. Patients in the BiVP group were programmedto simultaneous RV-LV timing (no interventricular offset).

Electrocardiographic analysis

Twelve-lead–paced ECGs of the 356 patients enrolled inthis study were studied. Further analyses were performed onthose ECGs with paced RBBB morphology. Threecardiologists reviewed the ECGs. The following variableswere analyzed:

1. The mean frontal-paced QRS axis.2. Paced QRS duration that relates in part to ventricular

function (ventricular dimensions and ejection fraction)and nonpaced QRS duration.

3. QRS pattern in V1: an overall positive QRS complex inV1 irrespective of the presence of an S wave is called anRBBB pattern of depolarization, whereas an overallnegative QRS complex in lead V1 is called a leftbundle-branch block (LBBB) pattern of depolarization.The lead V1was recorded in the fourth intercostal spacein patients.

4. QRS amplitude in lead V1.5. QRS configuration such as monophasic R pattern, twin

peaks pattern (or M-shaped pattern), a triphasic pattern(rSR′ pattern), Rs pattern, or qR pattern.

6. Concordance (all QRS complexes pointing in the samedirection in ECG leads V1 through V6) or discordance.

7. Precordial transition or transition lead if the precordialsequence is discordant. In patients with a discordantprecordial sequence, the RBBB pattern from pacingRV site results in a vector change from positive tonegative by a lead in the precordial sequence, and thisis referred to as the transition lead.

Pacing lead location analysis

The RV lead was placed in the apical position in thepatients in this study, and this was verified by a chest x-ray.The LV pacing lead position was determined by the chest x-ray (posteroanterior and lateral chest radiography). The LVlead position by the lateral view of the chest x-ray wascategorized as follows, as shown in Fig. 1:

1. Anterior (between 12 o'clock and 1 o'clock).2. Anterolateral (between 1 o'clock and 2 o'clock).3. Lateral (between 2 o'clock and 4 o'clock).4. Posterolateral (between 4 o'clock and 5 o'clock).5. Posterior (between 5 o'clock and 6 o'clock).

The LV lead location was verified by the coronary sinusvenography during implantation of each BiV pacemaker.

Statistical analyses

The SPSS 17 (SPSS Inc, Chicago, IL) statisticalprogram was used. Continuous data are presented asmean ± SD. Differences in clinical and demographicparameters between patients were evaluated by the Studentt test for continuous variables and Fisher exact test forcategorical variables. A P value of b.05 was consideredstatistically significant.

Results

Patients who had RV pacemaker placement at theMassachusetts General Hospital from January 2005 untilJanuary 2007 were included in the study. The results arebased on the data set used in this study, and a different

Table 2Patient characteristics with RBBB ECG pattern

Variable RVP (n = 50) BiVP (n = 50) P

Age (y) 67.8 ± 9.7 69.1 ± 10.6 .52Sex, n (% male) 40 (80) 39 (7%) 1.0Mean paced QRS axis (degr.) 290.0 ± 9.0 243.0 ± 11.0 b.0001Quadrant of mean paced QRS axis .0001Left superior, n (%) 38 (76) 18 (36)Right superior, n (%) 12 (24) 32 (64)Mean paced QRS duration (ms) 174.6 ± 4.4 157.4 ± 3.8 b.0001Mean R/S ratio in lead V1 2.3 ± 0.3 2.5 ± 0.8 .10Discordance, n (%) 43 (86) 50 (100) .01

All dimensions are expressed as mean ± SD.

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conclusion could be brought out if another data set isexamined. The study population included patients who had asingle- or dual-chamber pacemaker or an ICD with RVP.Only patients who had RV apical pacing and who had anECG after the pacemaker placement with a paced rhythmwere included in this study. Three hundred two patientsfulfilled those criteria, as follows: 50 patients had RBBB

Fig. 2. Electrocardiogram of a patient with a discordant precordial sequence and aThe posteroanterior chest x-ray is showing dual chamber with RV apical pacing (

morphology and 252 had LBBB morphology (Table 1).Patients who had a BiV pacemaker or ICD placement with anRV apical lead at the Massachusetts General Hospital werealso analyzed. Paced ECGs from 54 consecutive patientswere analyzed. Of the 54 patients, 50 (93%) had RBBBmorphology and 4 (7%) had LBBB morphology. Therefore,the BiVP group with paced RBBB pattern on ECGs included50 patients.

Paced LBBB was much more common with RVcompared with BiV pacing (P b .0001). The 4 patientswith LBBB morphology had a negative concordant pre-cordial sequence (R/S ratio b1). Those 4 patients had QSconfiguration in lead V1, and the LV was paced via a lead inthe middle cardiac vein as determined by coronaryvenography. A paced RBBB is much more common withBiV vs RV pacing (P b .0001). The percentage of patientswith RV apical pacing who had a paced RBBB morphologywas 16.6%.

The ECGs of the 50 patients with paced RBBBmorphology after conventional RV apical pacing were

late transition lead (V5) in a patient after conventional RV apical pacing (A)B).

.

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analyzed; as shown in Table 2, the mean frontal-paced QRSduration and the mean frontal-paced QRS axis weresignificantly different from the QRS duration and axis ofBiVP patients. The frontal plane mean QRS axis was mainlyin the left superior quadrant in RVP patients. On the otherhand, the frontal plane mean QRS axis in patients with BiVPwas mainly in the right superior quadrant.

In the RVP group, there was a positive concordance in 7patients and discordance in the other 43 patients. Thetransition lead was V1 in 3 patients (6%), V2 in 22 patients

Fig. 3. Electrocardiogram of a patient with LBBB morphology and a negative cochamber with RV apical pacing (B).

(44%), V3 in 11 patients (22%), V4 in 4 patients (8%), andV5 in 3 patients (6%). Fig. 2 illustrates a late transition leadby lead V5 in a patient after conventional RV apical pacing.Fig. 3 illustrates the ECG from a patient with RVP with anLBBB-paced QRS morphology and a negative concordantprecordial sequence. There was 100% discordance in theprecordial sequence of the 50 patients with BiVP and RBBB-paced ECG morphology.

The configuration of the precordial lead V1 in RVP wasanalyzed, as follows: 23 patients (46%) had Rs pattern, 16

ncordant precordial sequence (A). The lateral chest x-ray is showing dua

l

Table 3Paced QRS configurations and transition leads in patients with RBBBECG pattern

Variable RVP (n = 50) BiVP (n = 50) P

QRS configuration in lead V1 .0004⁎

Rs pattern, n (%) 23 (46) 32 (64)qR pattern, n (%) 16 (32) 0 (0)Monophasic R pattern, n (%) 4 (8) 11 (22)Twin peaks pattern, n (%) 4 (8) 4 (8)Triphasic pattern, n (%) 3 (6) 3 (6)Transition lead .0001⁎⁎

V1, n (%) 3 (6) 23 (46)V2, n (%) 22 (44) 21 (42)V3, n (%) 11 (22) 6 (12)V4, n (%) 4 (8) 0 (0)V5, n (%) 3 (6) 0 (0)

⁎ Overall χ2 is 20.7, and overall P value for association of RVP andBiVP with the 5 QRS configurations in lead V1 is .0004.

⁎⁎ Overall χ2 is 23.5, and overall P value for association of RVP andBiVP with the 5 transition leads is .0001.

Table 4Electrocardiographic characteristics with LV pacing lead location in the 50patients with cardiac resynchronization therapy and RBBB QRS pattern⁎

Patterns LV lead in thelateral vein(n = 30)

LV lead in theposterolateralvein (n = 20)

Late precordial transition(beyond lead V2)

1 5

Twin peaks or triphasicpattern of QRS in lead V1

1 6

⁎ P b .05.

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patients (32%) had a qR pattern, 4 patients (8%) had amonophasic R pattern, 4 patients (8%) had twin peaks pattern,and 3 patients (6%) had a triphasic pattern (Table 3). The

Fig. 4. Electrocardiogram of a patient with a qR configuration in lead V1 (A) that is(C) chest x-rays are showing dual chamber with RV apical pacing.

configuration of the precordial lead V1 in BiVP was analyzed,as follows: 32 patients (64%) had Rs pattern, 11 patients(22%) had a monophasic R pattern, 4 patients (8%) had twinpeaks pattern, and 3 patients (6%) had a triphasic pattern. Asshown in Table 3, none of the patients with BiVP had a qRpattern (Fig. 4 illustrates the ECG of one of the patients whohad a qR pattern with RV apical pacing). Of the 50 patients,30 (60%) had the LV paced via the lateral vein branch of thecoronary venous system, and 20 (40%) had the LV paced viathe posterolateral vein as verified by fluoroscopy andcoronary venography (Table 4). The patients with BiVP via

associated with RVP but not with BiVP . The posteroanterior (B) and latera

l

Fig. 5. Electrocardiogram of a patient with a triphasic pattern in lead V1 after BiV pacing via the posterolateral vein (A). The posteroanterior (B) and lateral (Cchest x-rays are showing the LV lead of the BiV/ICD via the posterolateral vein.

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a lateral vein had 3 configurations of the precordial lead V1, asfollows: Rs pattern, monophasic R, and twin peaks pattern.On the other hand, the patients with BiVP via theposterolateral vein had the following 4 configurations: Rspattern, monophasic R pattern, twin peaks pattern, and atriphasic pattern (Fig. 5 illustrates the ECG from one of thosepatients). The patients with LV pacing via the lateral vein hadan earlier transition lead than those with LV pacing via theposterolateral vein. In fact, 1 of 30 patients with LV lead in thelateral vein had a precordial lead transition beyond lead V2,whereas 5 of 20 patients with LV lead in the posterolateralvein had a precordial lead transition beyond lead V2 (Table 4).

Discussion

The growing number of patients with single-chamberpacemakers, dual-chamber pacemakers, and cardiac resyn-chronization devices makes the paced 12-lead ECG animportant tool in improving the care of patients. Theinformation from a single ECG lead is often limited, and a12-lead ECG provides a more precise evaluation in the

)

follow-up of patients with pacemakers. If a patient with apacemaker presents with paced “LBBB morphology” onECG, among the patients in our study, there was a 98%chance that it is RVP rather than BiVP. Although mostpatients with BiVP have paced RBBB pattern on ECG,approximately one sixth of patients with RV apical pacingalso have a similar paced RBBB pattern that is higher than thepreviously reported 8% to 10% by Coman and Trohman.13

Althoughwe did not identify any single variable that couldpredict RV or BiV pacing in all patients, we did find multiplesignificant variables that make RV or BiV pacing more likelyto be the pacing mode. In fact, we identified ECGcharacteristics with a paced RBBB QRS morphology thatwere encountered in RVP and not in BiVP (Tables 2 and 3).These include a qR complex morphology in lead V1

(sensitivity of 32% and specificity of 100%), a positiveconcordance in the precordial leads (sensitivity of 14% andspecificity of 100%), and a late QRS transition beyond leadV3 (sensitivity of 16% and specificity of 100%). If thosehighly specific patterns are seen when looking at an ECGfrom a cardiac resynchronization device, they can indicate

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significant changes in device performance, such as loss ofcapture of the LV lead. Our study showed as well that theBiVP complexes tend to have shorter paced QRS durationsthan RVP, and BiVP was associated with right superiorquadrant QRS axis (P b .05). Right ventricular pacing wasassociated with a mean frontal-paced QRS axis in the leftsuperior quadrant (P b .05) and had a sensitivity of 76% and aspecificity of 64%.

Furthermore, knowledge of the ECG characteristics ofventricular pacing from various sites in the coronaryvenous system is of importance at the time of implantationand for subsequent troubleshooting during follow-up.Some patterns on ECGs of BiVP have a diagnostic valuein predicting suboptimal LV lead placement from thetraditional target sites in the posterolateral and lateralcoronary veins that produce an RBBB pattern in lead V1.In a few instances, BiVP will result in an LBBB pattern ofventricular conduction if the LV lead is dysfunctional orthe LV lead is in the middle cardiac vein. In fact, an ECGpattern of LBBB during BiVP might suggest that thepacing site of the LV lead is not in the lateral orposterolateral coronary veins, and this might be helpful inthe diagnostic evaluation of suspected lead misplacementor nonresponse to cardiac resynchronization therapy.Similar to a previous study by Barold et al,7 we foundthat a minority of patients who underwent BiV pacemakerplacement with an apical RV lead had a paced LBBBmorphology, and in those patients, the LV pacing lead wasplaced via the middle cardiac vein. Another study showedas well an LBBB pacing pattern in BiVP with LV lead inthe middle cardiac vein or in distal pacing site in the greatcardiac vein.14

Furthermore, we identified ECG patterns that weresignificantly associated with a more posterior LV leadlocation (Table 4). These patterns include a late pre-cordial transition, especially beyond lead V2 and QRSconfigurations in lead V1 that include twin peaks ortriphasic pattern.

Limitations

Our study is limited by a relatively small number ofpatients. The findings are based on the data set used in thisstudy, and a different conclusion could be brought out ifanother data set is examined. Patients with the RV lead insites other than the RV apex were excluded from this study,and these patients could show different paced QRS patternscompared with the patients in our study. In addition, theeffect of interventricular offset (RV-LV timing) on thepaced RBBB pattern in patients with BiVP was not assessedin our study.

Conclusion

The 12-lead–paced ECG is a simple, inexpensive, andvaluable tool in the evaluation of pacemakers. Even amongpatients with a paced RBBB pattern, the 12-lead ECG canhelp distinguish RVP from BiVP and may help determineLV lead location for some cases during BiVP. Thisinformation may be useful in evaluating nonresponse toBiVP resulting either from LV noncapture (with consequentRVP) or from suboptimal LV lead location during BiVP.

Acknowledgment

We would like to acknowledge the advice and guidanceof Dr Peter Yurchak in the implementation of this project.

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