Effect of preexisting bundle branch block on the electrocardiographic diagnosis of ventricular tachycardia

Effect of Preexisting Bundle Branch Block on the Electrocardiographic Diagnosis of Ventricular Tachycardia Mark S. Kremers, MD, William H. Black, MD, Peter J. Wells, MD, and Martha Solodyna, RN

The electrocardiograms (ECGs) of 80 ventricular tachycardias (VTs) occurring in 52 patients with a normal baseline QRS duration (group 1) were compared with 26 VTs in 18 patients with preexisting bundle branch block (group 2). The effects of bundle branch block on the sensitivity of previously defined electrocardiographic criteria for differentiating VT from supraventricular tachycardia with aberration were under investigation. Specificity was examined by comparing VT to the baseline ECG in group 2 patients. The VTs in groups 1 and 2 were comparable with respect to rate, bundle branch pattern, R-wave pattern in VI with right bundle, frequency of an R/S ratio 30 ms R wave in VI or Vp with left bundle pattern was less frequent (18 vs 63%, p = 0.015) in group 2 vs group 1 arrhythmias. Right bundle pattern VT usually had a monophasic R wave in VI (69%), whereas preexisting right bundle usually had a biphasic R wave in VI (82%, p = 0.001). The quadrant of the frontal plane axis was significantly different between the VT ECGs and the ECGs with preexisting bundle branch block (p = 0.029) with a right superior quadrant axis only seen in VT (19%). A >30 ms R wave in VI or VZ with left bundle was also only seen in VT (52 vs 0%, p = 0.052). These data suggest that the sensitivity for VT of a >30 ms R wave in VI or VZ with left bundle pattern is diminished by preexisting bundle branch block but the sensitivity of other ECG markers of VT are not affected. Precordial QRS concordance, a monophasic R wave in VI, a right superior axis and a >30 ms R wave in VI or V2 with left bundle are infrequently seen with preexisting bundle branch block and therefore should suggest a diagnosis of VT even if a baseline ECG is unavailable. (Am J Cardiol 1988;62:1208-1212) From the Department of Internal Medicine, Cardiology Division, the University of Texas Southwestern Medical Center at Dallas, and the Electrophysiology Laboratory, Parkland Memorial Hospital, Dallas, Texas. Manuscript received June 21,1988; revised manuscript received August 4, 1988, and accepted August 7. Address for reprints: Mark S. Kremers, MD, Cardiology Division, University of Texas Southwestern Medical Center, 5323 Harry Hines Boulevard, Dallas, Texas 75235-9034.

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he differentiation of supraventricular tachycardia with a wide QRS from ventricular tachycardia (VT) is a difficult diagnostic problem upon which important therapeutic decisions are based.‘e3 Multiple electrocardiographic criteria have been proposed to assist in this differentiation including ,certain QRS morphologic patterns.4-9 The best known QRS patterns were described by Wellens et al* and were derived from patients with normal baseline electrocardiograms (ECGs). However, their value when the baseline ECG is abnormal or unavailable is incompletely defined. We examined the effect of preexisting bundle branch block on several electrocardiographic markers of VT by comparing the ECGs of sustained VT in patients with normal baseline QRS complex duration to those of patients with preexisting bundle branch block. In this manner, we sought to determine if the sensitivity of proposed QRS criteria for diagnosing VT are affected by an abnormal baseline tracing. We also compared the baseline ECGs with preexisting bundle branch block to those of VT to determine the specificity of the QRS morphologic patterns.

T

METHODS

The 12-lead ECGs during sinus rhythm and VT of all patients who had sustained uniform VT (2 15 beats) induced and confirmed at electrophysiologic study at Parkland Memorial Hospital or the Veterans Administration Hospital in Dallas, Texas, from February 1984 to December 1987 were evaluated in this study. Electrophysiologic study was performed in a standard fashion after discontinuing all antiarrhythmic drugs for >5 half-lives. VT was confirmed by the inability to record a His potential, the presence of atrioventricular dissociation, or both. ECGs were recorded with a Nihon-Koden or Marquette Electronics machine at a paper speed of 25 mm/s and 1 mV/cm amplification. All ECGs were independently graded by 3 of us for cycle length, mean frontal plane QRS axis and QRS pattern. Disagreements were resolved by discussion and mutual consent. The baseline QRS was considered of normal duration if it was <120 ms. Bundle branch block was diagnosed when the baseline QRS width was 2 120 ms. The QRS was scored as right bundle branch block if there was a dominant R wave in lead Vl. The R-wave pattern was graded as monophasic, biphasic, triphasic left (Rsr’) or triphasic right (rsR’) (Figure 1). To be considered multiphasic, the negative deflection(s) had to extend either to, or below, the baseline. R waves with

TABLE

I Ventricular

Number Cycle length (ms) Right bundle (%) Monophasic R (%) Biphasic R (%) R/S V,j 30 (%) Q wave V6 (%) AV dissociation (%) Concordance (%) Axis -90

to 00 (%) 0 to 900 (%) 90 to 180° (%) -90 to -180° (%)

Tachycardia

Characteristics

Group 1

Group 2

p Value

80 359 f 87 56 69 27 66 44 63 29 35 15

26 348 f 70 58 69 31 80 42 18 45 38 35

NS NS NS NS NS NS NS 0.015 NS NS 0.045 NS

57 10 16 16

morphology in Vi, the proportion with an R/S 30 ms wide in Vt or VZ was seen in 63% of left bundle VTs in group 1 versus 18% in group 2 (p = 0.015). Precordial concordance during VT was more frequent in group 2 than in group 1 (35 vs 15%, p = 0.045) (Figure 2). Group 2 baseline tracing versus ventricular tachycardia: A significant difference was found in the R

wave in VI between right bundle pattern VTs and sinus rhythm tracings (Table II, Figure 3). In 69% of the VT tracings, a monophasic R wave was seen in VI. However, a biphasic R wave in Vi was demonstrated in 82%

35 15 23 27

a.

R/S Vs 30 = R wave >30 rns wide in v, or VP.

lesser negative deflections were considered notched monophasic patterns. With right bundle, the QRS in V6 was also graded for an R/S ratio 30 ms in Vi or VZ was recorded.9 In the VT ECGs, the presence of atrioventricular dissociation and precordial QRS concordance was also noted. In several patients, multiple VTs with distinct bundle branch block patterns and axes (different quadrant) were observed and scored. Because VTs recorded before and after antiarrhythmic drug testing were included, QRS width was not evaluated. Comparisons were made between the VT in patients with a normal baseline QRS duration (group 1) to those with preexisting bundle branch block (group 2). In addition, the QRS pattern of the baseline ECGs in group 2 were compared to the VT ECGs in the entire population. Statistical analysis: Continuous variables were analyzed using a t test. The means are reported with the standard deviation. Categorical variables were analyzed with chi-square and Fisher’s exact test. Statistical significance was at the level of p <0.0.5.

MONOPHASIC

d

BIPHASIC

RESULTS There were 106 ECGs of sustained VT recorded in 70 patients (59 men and 11 women). In 52 patients (group l), the baseline QRS was of normal duration and in 18 (group 2), bundle branch block was present. Group 1 and 2 patients were comparable with respect to age, sex, form of heart disease and incidence of previous myocardial infarction. Patients in group 2 more frequently had anterior infarctions compared with those in group 1 (86 vs 57%; p = 0.015). Patterns of ventricular tachycardia in group 1 versus group 2: There were 80 distinct VTs in group 1

(1.5/patient) and 26 in group 2 (1,4/patient, difference not significant) (Table I). VT in groups 1 and 2 was similar with respect to cycle length, axis, presence of antiarrhythmic drugs, incidence of atrioventricular dissociation and bundle branch block pattern. The R-wave

TRIPHASIC FIGURE 1. Right bundle branch block QRS patterns in lead VI are demonstrated. Monophasic patterns showed either a smooth R wave (a) or notches that did not reach the baseline (/J). Riphasic complexes showed either a qR (c) or Rs (d) pattern. Triphasic patterns had negative deflection that reached or crossed the baseline and were subdivided into left (e) or right (Q patterns. Pattern f was not seen in this study and is from a patient with supraventricular tachycardia.

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of the sinus rhythm tracings (p
An R/S
aVR

FIGURE 2. A left bundle-morphology the concordance of the precordial

ventricular QS complexes

Ill

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tachycardia from a patient in group 2 with and the absence of a >30 ms wide R wave

aVR

VOLUME

aVL

62

aVF

aVL

aVF

a previous anterior infarction. Note in VI or Vs. The axis is in the right

FIGURE 3. Right bundle QRS morphologies in sinus rhythm (A) and ventricular tachycardia (B) from a patient in group 2. Note the biphasic R wave in Vi in A and the monophasic R wave in VI in B.

V2 >30 ms was seen in 52% of VTs compared with 0% of sinus rhythm tracings (Figure 4). This nearly reached statistical significance (p = 0.052). The frontal plane axis with VT was different than that seen in the abnormal baseline tracings (p = 0.029). In particular, a right superior quadrant axis (-90’ to -180’) was seen in 19% of the VTs (Figure 2) but none of the abnormal baseline ECGs. DISCUSSION

TABLE

II QRS Patterns

Pattern

Ventricular Tachycardia

Group 2 Baseline

Right bundle (%) Monophasic R (%) R/S V6 30 (%) Q wave V6 (%%j

57 69 70 43 52 33

61 0 45 39 0 20

52 11 18 19

75 19 6 0

NS
NS NS 0.052

NS 0.029

Axis

Tachycardia with a wide QRS complex may be VT or supraventricular tachycardia conducted with bundle branch block or preexcitation. Several investigators4J,9 have shown that supraventricular tachycardia conducted with bundle branch block can be differentiated from VT based on differences in certain QRS patterns. However, these findings were primarily derived from patients with baseline normal conduction and functional aberrancy. In this study we found that electrocardiographic appearance of VT was minimally affected by preexisting bundle branch block. A >30 ms R wave in V1 or V2 occurred less frequently and QRS concordance more

-90

to 00 (%)

0 to +900 +90 to +180” -90 to -180° Abbreviations

(%) (%) (“/a)

p Value

as in Table I.

frequently with preexisting bundle branch block than with a normal baseline QRS. We believe these differences were due to the higher incidence of anterior infarction in patients with bundle branch block. This decreases the frequency of a >30 ms R wave in left bundle VT9 and may cause precordial QS patterns. The sensitivity for VT of a >30 ms R wave in VI or VZ with

A. I

aVR

aVL

aVF

aVR

aVL

aVF

FIGURE 4. Left bundle QRS morphologies in sinus rhythm (A) and VT (B) (different patients). Note the >30 ms wide R wave in VI in B and the narrow R waves in VI and Vz in A (arrows). A Q wave in Vs is also shown in

B.

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left bundle is therefore diminished by preexisting bundle branch block. However, its absence in preexisting left bundle suggests its specificity is not altered. Similarly, precordial concordance was not evident in any sinus ECG and should therefore be a relatively specific clue to the diagnosis of VT. In patients with normal baseline QRS patterns and wide QRS tachycardias, Wellens et al8 found that monophasic, biphasic or triphasic left (Rsr’) R-wave patterns in Vt, an R/S
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may have virtually identical QRS appearances in the same patient,’ 1 we included only ECGs whose mechanism was confirmed at electrical study. However, the QRS pattern during supraventricular tachycardia in patients with preexisting bundle branch block is similar to that observed during sinus rhythmI and supports this approach. Nonetheless, we cannot rule out minor changes in configuration that might occur with tachycardia that could affect these results. Drug therapy in some patients may have also altered the QRS pattern. However, patients frequently present with arrhythmias while taking medication and therefore this should not affect the clinical value of our findings. This study, therefore, does not directly address the electrocardiographic differentiation of VT from supraventricular tachycardia with a wide QRS. Nonetheless, our data provide insight into the potential value and limitations of the QRS criteria-derived from studies of VT and supraventricular tachycardia with functional bundle branch block-to arrhythmia diagnosis when no baseline tracing is available, or when the baseline tracing showsfixed bundle branch block. In addition to being infrequent in patients with functional aberration, a monophasic R wave in VI, QRS concordance, a right superior axis and a >30 ms R wave in Vi or V2 with left bundle pattern are infrequent in patients with preexisting bundle branch block and therefore may be relatively specific for VT. However, these were only seen in 38, 21, 19 and 2376, respectively, of VT ECGs and therefore show poor sensitivity.

REFERENCES 1. Stewart RB, Bardy GH, Greene HL. Wide complex tachycardia: misdiagnosis and outcome after emergent therapy. Ann Intern Med 1986;104:766-771. 2. Dancy M, Camm AJ, Ward D. Misdiagnosis of chronic recurrent ventricular tachycardia. Lmcet 1985;2:320-323, 3. Morady F, Baerman JM, DiCarlo LA Jr, DeBuitleir M, Krol RB, Wahr DW. A prevalent misconception regarding wide-complex tachycardias. JAMA 1985; 254:2790-2792. 4. Sandier IA, Marriott H. The differential morphology of anomalous ventricular complexes of RBBB-type in lead Vi. Ventricular ectopy versus aberration. Circulation 1965;31:551-563. 5. Kistin AD. Problems in the differentiation of ventricular arrhythmias from supraventriculararrhythmia with abnormal QRS. Prog Cardiouasc Dis 1966:9;117. 6. Marriott HJL, Sandier JA. Criteria, old and new, for differentiating between ectopic ventricular beats and aberrant ventricular conduction in the presence of atrial fibrillation. Prog Cardiomsc Dis 1966;9:18-28. 7. Kuchar DL, Thorburn CW, Sammel NL, Garan H, Ruskin JN. Surface electrocardiographic manifestations of tachyarrhythmias: Clues to diagnosis and mechanism. PACE 1988;11:61-82. 6. Wellens HJJ, Blr FW, Lie KI. The value of the electrocardiogram in the differential diagnosis of a tachycardia with a widened QRS complex. Am J Med 1978;64:27-33. 9. Kindwall KE, Brown J, Josephson ME. Electrocardiographic criteria for ventricular tachycardia in wide complex left bundle branch morphology tachycardias. Am J Cardiol 1988;61:1279-1283. 10. Wellens HJJ, B%r FW, Vanagt EJ, Brugada P, Farre J. The differentiation between ventricular tachycardia and supraventricular tachycardia with aberrant conduction: the value of the 124ead electrocardiogram. In: Wellens HJJ, Kulbertus HE, eds. What’s New in Electrocardiography. The Hague: Martinus Nijhoff; 1981:184-199. 11. Ross DL, Vohra JK, Sloman JG. Similar QRS morphology in sinus rhythm and ventricular tachycardia. PACE 1979;2:486-489. 12. Dongas J, Lehmann MH, Muhmud R, Denker S, Soni J, Akhtar M. Value of preexisting bundle branch block in the electrocardiographic differentiation of supraventricular from ventricular origin of wide QRS tachycardia. Am J Cardiol 198X55:71 7-721.