Outcomes in patients with chronicity of left bundle- branch block with possible acute myocardial infarction Michael C. Kontos, MD, FACC, a,b Hammad A. Aziz, MD, a Vinh Q. Chau, BS, a Charlotte S. Roberts, MSN, a Joseph P. Ornato, MD, FACC, b and George W. Vetrovec, MD, FACC a Richmond, VA Introduction Guidelines derived from patients in clinical trials indicate that emergency department patients with likely myocardial infarction (MI) who have new left bundle-branch block (LBBB) should undergo rapid reperfusion therapy. Whether this pertains to lower risk emergency department patients with LBBB is unclear. Methods A total of 401 consecutive patients with LBBB undergoing an MI rule-out protocol were included. Left bundle- branch blocks were classified as chronic; new; or, if no prior electrocardiogram (ECG) was available, as presumably new. Left bundle-branch blocks were considered concordant if there was ≥1 mm concordant ST elevation or depression. Rates of MI, peak MB values in MI patients, and 30-day mortality were compared across groups. Results A majority of patients (64%) had new (37%) or presumably new LBBB (27%). A total of 116 patients (29%) had MI, with no significant difference in prevalence or size of MI among the 3 ECG groups. Myocardial infarction was diagnosed in 86% of patients with concordant ECG changes versus 27% of patients without concordant ECG changes (P b .01). Peak MB was N5× normal in 50% who had concordant ST changes compared to none of those who did not. Concordant ST changes were the most important predictor of MI (odds ratio 17, 95% CI 3.4-81, P b .001) and an independent predictor of mortality (odds ratio 4.3, 95% CI 1.3-15, P b .001); new or presumably new LBBB was neither. Conclusions Most patients with possible MI with new or presumably new LBBB do not have MI. Concordant ECG changes were an important predictor of MI and death. Current guidelines regarding early reperfusion therapy for patients with LBBB should be reconsidered. (Am Heart J 2011;161:698-704.) Patients with left bundle-branch block (LBBB) represent Methods an important minority of patients with suspected acute The chest pain protocol used at our institution has been coronary syndrome. Current recommendations from the described in detail previously.12 Patients with possible myocardial American College of Cardiology/American Heart Associ- ischemia undergo an evaluation by emergency department (ED) ation1 and European Society of Cardiology2 indicate that physicians, with further treatment and evaluation dictated based on patients with new or presumed new LBBB should the initial risk stratification.12 Patients were included in this analysis undergo early reperfusion therapy (fibrinolytics or if they presented with possible myocardial ischemia, underwent primary percutaneous coronary intervention [PCI]), serial marker assessment, and had an LBBB on the initial ED ECG. although this occurs in only a minority.3-5 However, Data were collected prospectively as part of an ongoing quality early reperfusion treatment may not be appropriate for all assurance process using a standardized data collection form with retrospective analysis of patient's records to supply mission patients with new LBBB because only a minority is information. This study was approved by the Committee on the diagnosed with myocardial infarction (MI).6-8 In contrast, 9 Conduct on Human Research at Virginia Commonwealth Univer- objective electrocardiographic (ECG) criteria may iden- sity. Of patients included in the current study, 182 were included in tify those who have larger MIs in whom treatment is more apriorpublication6 and have been combined with an additional 10,11 likely to be beneficial. 219 patients to form the current analysis. Therefore, we assessed the effect of the chronicity of LBBB on outcomes in patients with possible acute MI. Electrocardiographic interpretation Left bundle-branch block wasdefinedasthepresenceofaQRS a ≥ From the Division of Cardiology, Department of Internal Medicine, Virginia Common- duration of 120 milliseconds, a QS or rS complex in lead V1,and wealth University, Richmond, VA, and bPauley Heart Center, and Department of an R wave peak time of at least 60 milliseconds in the absence of Q Emergency Medicine, Virginia Commonwealth University, Richmond, VA. waves in leads I, V5,orV6. Concordant ECG changes were Submitted October 6, 2010; accepted January 8, 2011. considered present if 1 of 2 previously defined criteria for acute Reprint requests: Michael C. Kontos, MD, PO Box 980051, Richmond, VA 23298-0051. myocardial infarction (MI) were present9:ST-segmentelevation≥1 E-mail: [email protected] 0002-8703/$ - see front matter mm concordant with the QRS complex or ST-segment depression ≥ © 2011, Mosby, Inc. All rights reserved. 1mminleadsV1,V2,orV3. In addition, a third criterion was also 13 doi:10.1016/j.ahj.2011.01.008 analyzed: the ratio of the ST segment to the S wave ≥25%. All American Heart Journal Kontos et al 699 Volume 161, Number 4 Table I. Demographics and risk factors based on chronicity of the LBBB New or unknown All patients, Chronic LBBB, New LBBB, Unknown duration, duration, N = 401 n = 145 n = 147 n = 109 n = 256 Age, y 66 ± 14 (66) 67 ± 14 (67) 65 ± 14 (64) 67 ± 16 (68) 66 ± 15 (66) Age ≥65 y 193 (48) 71 (49) 60 (41) 62 (56) 122 (48) ⁎ Male 158 (39) 46 (32) 63 (43) 45 (45) 112 (44) Hypertension 312 (78) 118 (81) 120 (83) 73 (66) 193 (75) Diabetes 157 (39) 52 (36) 66 (46) 38 (35) 104 (41) CHF 95 (24) 42 (29) 33 (23) 30 (27) 63 (25) EF, % 36 ± 16 (33) 35 ± 16 (32) 37 ± 18 (35) 34 ± 15 (30) 36 ± 17 (33) EF b40% 219 (61) 80 (62) 78 (58) 60 (64) 138 (60) † Prior MI 109 (27) 50 (34) 39 (27) 20 (18) 59 (23) † Prior revascularization 103 (27) 50 (34) 41 (28) 17 (15) 58 (23) CrCl, mL/min 59 ± 31 (57) 57 ± 33 (55) 59 ± 30 (60) 62 ± 32 (56) 60 ± 32 (56) CrCl b60 mL/min 201 (53) 76 (56) 66 (49) 58 (55) 124 (51) TnI MI 116 (30) 46 (32) 35 (24) 35 (32) 70 (27) CK-MB MI 93 (23) 32 (22) 32 (22) 29 (27) 61 (24) Peak CK-MB, ng/mL 18 (11, 45) 17 (12, 37) 19 (10, 48) 23 (10, 54) 19 (10, 52) Peak CK, U/L 350 (190, 590) 250 (180, 450) 470 (230, 750) 390 (170, 680) 400 (200, 710) Categorical data are presented as n (%). Continuous data are presented as mean ± SD (median). Peak CK and CK-MB values were calculated in the subgroup of patients who had MI and are presented as median (25th, 75th percentiles). CrCl, Creatinine clearance. ⁎ P b .05 compared to patients with new LBBB. † P b .01 compared to unknown duration LBBB. ECGs were read independently by 2 interpreters unaware of the initial creatinine. Significant coronary disease was defined as a clinical variables and patient outcome. Disagreements were stenosis ≥50% in a coronary artery or its branches or in a resolved by a third interpreter (3% of cases). The chronicity of coronary bypass graft. the LBBB was determined by comparison with the most recent previous ECG available in our hospital's computerized ECG records. An LBBB was considered new if the most recent, available ECG was Statistical analysis not LBBB. If no prior ECG was available for comparison, patients Comparisons were made among patients with chronic LBBB, were classified as having presumed new LBBB. Patients who had new LBBB, and presumed new LBBB. Because patients with new LBBB on the most recent prior ECG were classified as having or presumed new LBBB are considered candidates for early chronic LBBB. reperfusion treatment, they were combined for several analyses. Student t test or χ2 analysis was used for categorical and Definitions proportional variables, respectively. P =.05 was considered statistically significant. Significant univariate variables at P b .10 All patients underwent serial sampling of total creatine kinase were included in a multivariate analysis to identify independent (CK)–MB (CK-MB) and troponin I (TnI). Diagnosis of MI predictors of acute MI and 30-day mortality. Statistical analysis required at least 1 TnI value that exceeded the reference was preformed with a standard statistical software package (SAS range (coefficient of variation b10% for that assay) with a 6.11, SAS, Cary, NC). serial rise and fall. Five different assays for CK-MB and TnI were used: the Opus Magnum Analyzer (Boston, MA) (diagnos- The authors are solely responsible for the design and conduct tic value 1.0 ng/mL, June 1996-May 1998), the Bayer Immuno of this study, all study analyses, and the drafting and editing of One assay (Tarrytown, NY) (diagnostic value 0.3 ng/mL, May the paper and its final contents. 1998-April 2000), the DPC assay (Los Angeles, CA) (diagnostic value 1.0 ng/mL, April 2000-December 2002), the Bayer TnI assay (Tarrytown, NY) (diagnostic value 0.5 ng/mL, December 2002-April 2007), and the Bayer TnI Ultra Assay (Tarrytown, Results NY) (diagnostic value 0.1 ng/mL, April 2007-end of the study). Clinical characteristics Because different TnI assays were used, infarct size was From 1994 to 2009, 401 consecutive patients who estimated using peak CK-MB values obtained during the initial underwent evaluation for possible acute coronary syn- 24 to 36 hours after admission. The number of patients who had drome had LBBB on the initial ECG and were included in N CK-MB MI (CK-MB 6 ng/mL) in conjunction with an elevated this analysis. In general, the patient population was older TnI was also determined. Size of MI was described based on (median age 66 years), with frequent comorbidities multiples of peak CK and CK-MB.