Clinical Characteristics, Management, and Outcomes of Acute Coronary Syndrome in Patients With Right Bundle Branch Block on Presentation

Accepted Manuscript Clinical Characteristics, Management, and Outcomes of Acute Coronary Syndrome in Patients With Right Bundle Branch Block on Presentation William K. Chan, MD, Shaun G. Goodman, MD, MSc, David Brieger, MBBS, PhD, Keith AA. Fox, MB, ChB, FRCP, Chris P. Gale, MD, Derek P. Chew, MD, Jacob A. Udell, MD, MPH, Jose Lopez-Sendon, MD, Thao Huynh, MD, Raymond T. Yan, MD, Sheldon M. Singh, MD, Andrew T. Yan, MD PII:

S0002-9149(15)02348-6

DOI:

10.1016/j.amjcard.2015.12.005

Reference:

AJC 21581

To appear in:

The American Journal of Cardiology

Received Date: 25 September 2015 Revised Date:

29 November 2015

Accepted Date: 1 December 2015

Please cite this article as: Chan WK, Goodman SG, Brieger D, Fox KA, Gale CP, Chew DP, Udell JA, Lopez-Sendon J, Huynh T, Yan RT, Singh SM, Yan AT, on behalf of the ACS I and GRACE investigators, Clinical Characteristics, Management, and Outcomes of Acute Coronary Syndrome in Patients With Right Bundle Branch Block on Presentation, The American Journal of Cardiology (2016), doi: 10.1016/j.amjcard.2015.12.005. This is a PDF file of an unedited manuscript that has been accepted for publication. As a service to our customers we are providing this early version of the manuscript. The manuscript will undergo copyediting, typesetting, and review of the resulting proof before it is published in its final form. Please note that during the production process errors may be discovered which could affect the content, and all legal disclaimers that apply to the journal pertain.

ACCEPTED MANUSCRIPT 1 Clinical Characteristics, Management, and Outcomes of Acute Coronary Syndrome in Patients With Right Bundle Branch Block on Presentation William K Chan, MD1,2, Shaun G Goodman MD, MSc1,2,3, David Brieger MBBS, PhD4, Keith AA

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Fox MB, ChB, FRCP5, Chris P Gale MD6, Derek P Chew MD7, Jacob A Udell MD, MPH2,8, Jose Lopez-Sendon MD9, Thao Huynh MD10, Raymond T Yan MD2, Sheldon M Singh MD2,11, Andrew T Yan MD1,2 on behalf of the ACS I and GRACE investigators

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From the 1Terrence Donnelly Heart Centre, St Michael’s Hospital, Toronto, Canada; 2 University

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of Toronto, Toronto, Canada; 3 Canadian Heart Research Centre, Toronto, Canada; 4 Coronary Care Unit, Concord Hospital, Sydney, Australia; 5 Centre for Cardiovascular Science, The University of Edinburgh, Edinburgh, UK; 6 Leeds Institute of Cardiovascular and Metabolic Medicine, University of Leeds, Leeds, UK; 7 Flinders University, Adelaide, South Australia, Australia; 8 Women's College Hospital and Toronto General Hospital, Toronto, Canada; 9Hospital

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Universitario La Paz, Madrid, Spain; 10 McGill University Health Centre, McGill University, Montreal, Canada; 11 Sunnybrook Health Sciences Centre, Toronto, Canada.

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Running title: Right bundle branch block and acute coronary syndrome

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GRACE was funded by an unrestricted grant from Sanofi-Aventis, Paris, France. The Canadian ACS Registry I was sponsored by the Canadian Heart Research Centre (a federally incorporated not-for-profit academic research organization) and Key Pharmaceuticals, Division of Schering Canada Inc. These sponsors had no involvement in the study conception or design; data collection, analysis, and interpretation; in the manuscript writing, review, or approval; or in the decision to submit the manuscript for publication. Corresponding Author: Dr. Andrew Yan, St. Michael's Hospital, 30 Bond St, Donnelly Room 6030, Toronto, Ontario, Canada M5B 1W8; Tel: 416-864-5465, Fax: 416-864-5159; E-mail: [email protected]

ACCEPTED MANUSCRIPT 2 ABSTRACT We examined the relationships between right bundle branch block (RBBB) and clinical characteristics, management, and outcomes among a broad spectrum of patients with acute

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coronary syndrome (ACS). Admission electrocardiograms (ECG) of patients enrolled in the

Global Registry of Acute Coronary Events (GRACE) ECG substudy and the Canadian ACS Registry I were analyzed independently at a blinded core laboratory. We performed multivariable

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logistic regression analysis to assess the independent prognostic significance of admission RBBB on in-hospital and 6-month mortality. Among 11,830 eligible ACS patients (mean age 65; 66%

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non-ST elevation ACS), 5% had RBBB. RBBB on admission was associated with older age, male sex, more cardiovascular risk factors, worse Killip class and higher GRACE risk score (all p<0.01). Patients with RBBB less frequently received in-hospital cardiac catheterization, coronary revascularization, or reperfusion therapy (all p<0.05). The RBBB group had higher unadjusted in-

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hospital (8.8% vs. 3.8%, p<0.001) and 6-month mortality (15.1% vs. 7.6%, p<0.001). After adjusting for established prognostic factors in the GRACE risk score, RBBB was a significant independent predictor of in-hospital death (OR 1.45, 95% CI 1.02-2.07, p=0.039), but not

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cumulative 6-month mortality (OR 1.29, 95% CI 0.95-1.74, p=0.098). There was no significant interaction between RBBB and type of ACS for either in-hospital or 6-month mortality (both

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p>0.50). In conclusion, across a spectrum of ACS, RBBB was associated with pre-existing cardiovascular disease, high-risk clinical features, fewer cardiac interventions, and worse unadjusted outcomes. After adjusting for known components of the GRACE risk score, RBBB was a significant independent predictor of early mortality. KEY WORDS: right bundle branch block, acute coronary syndrome, Global Registry of Acute Coronary Events

ACCEPTED MANUSCRIPT 3 INTRODUCTION Right bundle branch block (RBBB) in the context of acute coronary syndrome (ACS) is not an infrequent occurrence, ranging from 1.6-15% in hospitalized patients 1,2. Several studies

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demonstrate increased mortality in this high-risk group despite advances in therapeutics and early revascularization strategies 3–11. It is widely known that RBBB after anterior myocardial infarction (MI), caused by complete occlusion of the proximal left anterior descending (LAD) artery, is a

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predictor of mortality. In patients presenting with RBBB, those with ST-segment elevation MI (STEMI) undergoing fibrinolysis or angioplasty have poorer short- and long-term prognosis than

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those without STEMI. Investigators have recently called for updated reperfusion guidelines to reflect the adverse prognosis of new RBBB in ACS, even in the absence of ST elevation 8. Patients with non-ST elevation acute coronary syndromes (NSTE-ACS) comprise a heterogeneous group with variable prognoses that warrant early risk stratification to minimize adverse outcomes.

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NSTE-ACS with RBBB may predict worse outcomes due to more extensive underlying coronary artery disease as opposed to STEMI, where RBBB may reflect larger infarcts 12. Furthermore, prior studies were limited by small sample sizes usually from single centres, lacked blinded ECG

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interpretation, and did not adjust for other independent prognosticators in validated risk scores. Therefore, the objective of our study was to determine the relationship between presenting RBBB

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and clinical characteristics, in-hospital management, and clinical outcomes across a broad spectrum of patients with ACS, including NSTE-ACS and STEMI. METHODS

The Canadian ACS Registry I and Global Registry of Acute Coronary Events (GRACE)

were prospective, multi-centre, observational studies of the clinical characteristics, management, and outcomes of patients with NSTE-ACS and STEMI. Their rationale and design have been described elsewhere 13–16.

ACCEPTED MANUSCRIPT 4 In brief, the ACS Registry I enrolled patients from September 1999 to June 2001 across 51 Canadian hospitals (n=4627). Eligible patients were ≥18 years old and admitted to hospital for suspected ACS within 24 hours of symptom onset. ECGs from all patients were obtained at

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admission. GRACE included patients from 94 international sites ≥18 years old and admitted to hospital with a presumed diagnosis of ACS based on ischemic cardiac symptoms and at least 1 of the following: ECG changes, elevated biomarkers, and/or documented history of coronary artery

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disease. For the current study, we included patients from the GRACE ECG substudy involving 39 sites in 11 countries between March 1999 and January 2004 (n=7900). Both registries excluded

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patients if their presenting condition was triggered by another major comorbidity such as surgery, trauma, or gastrointestinal bleeding. All centres were encouraged to enroll consecutive patients to minimize selection bias.

All data on patient demographics, clinical presentation, investigations, management, and

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outcomes were recorded on standardized case report forms by local study coordinators or the responsible physician during index hospitalization. Forms for the ACS Registry were scanned into a central database (Teleform version 7.0, Cardiff, San Diego, CA) at the Canadian Heart Research

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Centre in Toronto, Canada. GRACE data were managed by a coordinating center at the University of Massachusetts (Worcester, MA). Central data checks were executed and queries forwarded to

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participating centers for clarification of sampling protocols. After hospital discharge, patients were followed up via telephone interviews at 6 months in GRACE and 12 months in the ACS Registry to ascertain vital status. Study protocols were approved by local review boards and all patients provided informed consent. Primary outcomes were in-hospital and cumulative 6-month all-cause mortality. Secondary outcomes included in-hospital myocardial (re)infarction (defined as new or recurrent beyond 24 hours of hospitalization) 17, heart failure (only recorded in GRACE), and the composite of death or myocardial (re)infarction.

ACCEPTED MANUSCRIPT 5 Admission ECGs were recorded at standard paper speed of 25 mm/s and calibration of 10 mm/mV and were forwarded to the Canadian Heart Research Centre ECG core laboratory for systematic interpretation. ECGs were read by trained physicians blinded to clinical data, site

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interpretation, and patient outcomes. The core laboratory has previously demonstrated interobserver and intra-observer agreements of 93–99% and 100%, respectively 18,19. We defined STsegment elevation as the presence of ≥ 0.1 mV ST-segment elevation in 2 contiguous leads; ST-

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segment depression as the presence of ≥ 0.05 mV ST-segment depression in ≥ 1 lead, excluding aVR; and T wave inversion as the presence of ≥ 0.1 mV deviation from the isoelectric baseline in

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2 contiguous leads. Pathological Q waves were defined as Q ≥ 30 ms in leads I, aVL, II, aVF; any Q in V1-V3; Q ≥ 20 ms in V4; Q ≥ 30 ms in V5-V6 when present in ≥ 2 contiguous leads. RBBB was coded if all the following criteria were met: (1) QRS duration of >120 milliseconds in the presence of normal sinus or supraventricular rhythm; (2) r or rSr′ complex in lead V1; and (3) rS

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in leads V5, V6, I, or aVL, with a prolonged shallow S wave 20. Patients with left bundle branch block, poor quality or incomplete ECGs, and ventricular-paced rhythms were excluded (n=697). Cardiac catheterization during the index hospitalization was undertaken at the discretion of

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the treating physician. Significant coronary artery stenosis was defined as ≥50% narrowing compared to the diameter of the adjacent normal segment, and three-vessel disease as significant

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stenosis in all 3 epicardial coronary arteries (i.e. left anterior descending, left circumflex, and right circumflex) or their main branches. Angiographic data were only available for patients who underwent cardiac catheterization from the GRACE ECG substudy (n=4277). Those with previous coronary artery bypass grafting (CABG) were excluded from the analysis of angiographic data. Continuous variables were expressed as medians with inter-quartile ranges, and categorical variables as percentages. We used non-parametric Mann–Whitney U and Pearson χ2 tests to

ACCEPTED MANUSCRIPT 6 examine differences in continuous and categorical variables, respectively. We performed multivariable logistic regression analysis to evaluate the independent prognostic significance of RBBB during index hospitalization and at 6 months, adjusting for known predictors of the in-

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hospital GRACE risk model (i.e., age, heart rate, systolic blood pressure, cardiac arrest, Killip class, serum creatinine, initial cardiac biomarker elevation, and ST-segment deviation) 21. The GRACE risk score for predicting cumulative 6-month mortality also included previous myocardial

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infarction and heart failure 22. The GRACE risk score has previously demonstrated excellent discrimination in external validation cohorts 23,24. Model discrimination and calibration were

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evaluated by the c-statistic and Hosmer–Lemeshow goodness-of-fit test, respectively. We tested for an interaction effect between RBBB and type of ACS (NSTE-ACS and STEMI) on mortality. All analyses were performed using SPSS v.22 (IBM) and statistical significance was set at a 2sided p value <0.05.

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RESULTS

Our study included 11,830 eligible patients with a mean (± SD) age of 65 (±13) years of whom 33% were woman and 66% had NSTE-ACS. Overall, 590 (5%) patients had RBBB on the

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presenting ECG.

Baseline characteristics of the patients are shown in Table 1. Patients with RBBB were

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older, more likely male, and had more cardiovascular co-morbidities. They also had higher rates of prior transient ischemic attack or stroke, congestive heart failure (CHF), peripheral vascular disease, and coronary artery disease. Patients with RBBB presented with higher heart rates and creatinine levels, worse Killip class; they more frequently had elevated initial cardiac biomarkers, and had higher GRACE risk scores (Table 2). They also were more likely to have ST depression, T-wave inversion, and Q waves in the precordial leads. However, patients with RBBB were less likely to present with ST elevation than those without RBBB.

ACCEPTED MANUSCRIPT 7 Table 3 summarizes in-hospital management for patients with and without RBBB. Patients with RBBB were less likely to receive fibrinolysis, cardiac catheterization, percutaneous coronary intervention, and CABG. Among 4277 patients who underwent coronary angiography (Figure 1),

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those with RBBB had higher rates of ≥50% stenosis in any coronary artery, left main stenosis, and triple vessel disease. Figure 2 summarizes the unadjusted clinical outcomes. The RBBB group had a lower left ventricular ejection fraction (LVEF) with a higher proportion of patients having

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moderately or severely diminished LV function compared to those without RBBB (Table 3), and correspondingly higher rates of in-hospital heart failure. In-hospital (re)infarction rates were not

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significantly different between those presenting with or without RBBB.

Overall, 485 (4.1%) patients died in hospital. Data on 6-month vital status were available for 89.1% of the study cohort; the 6-month mortality rate was 8.0%. Unadjusted rates of inhospital mortality (8.8% vs. 3.8%, p<0.001) and cumulative 6-month mortality (15.1% vs. 7.6%,

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p<0.001) were almost doubled in the RBBB group compared to the non-RBBB cohort. After adjusting for known prognostic factors in the GRACE risk models (Table 4), RBBB was independently associated with in-hospital mortality (OR 1.45 95% CI 1.02-2.07, p=0.039). The

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adverse prognostic value of RBBB was consistently observed across the groups with NSTE-ACS and STEMI (p for interaction=0.62). RBBB was numerically, but not statistically significantly

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associated with cumulative 6-month mortality (OR 1.29, 95% CI 0.95-1.74, p=0.098) (Table 5). The c-statistics were 0.85 and 0.83, and Hosmer-Lemeshow p values were 0.48 and 0.67, respectively, indicating good discrimination and calibration of the models. RBBB was not an independent predictor of the composite endpoint of in-hospital myocardial (re)infarction or death (OR 1.20, 95% CI 0.93-1.56, p=0.17). DISCUSSION

ACCEPTED MANUSCRIPT 8 In this cohort of patients with a broad spectrum of ACS, RBBB on the admission ECG was associated with high-risk clinical features, fewer cardiac interventions, multi-vessel disease, and worse unadjusted clinical outcomes. After adjusting for known GRACE risk score prognosticators,

was numerically but not significantly higher.

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RBBB remained a significant independent predictor of in-hospital mortality; 6-month mortality

RBBB is not infrequent in patients hospitalized with acute MI, ranging from 1.6-15%, and

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portends a poor prognosis regardless of fibrinolytic or interventional therapy 1–4,7. The infarct territory and size as well as the acuity of the event carry prognostic value in patients who present

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with RBBB. A new RBBB with anterior STEMI indicates septal injury and is therefore a marker of larger infarction involving the proximal LAD artery 10. Wong demonstrated that a longer QRS duration in RBBB had higher mortality in patients presenting with ACS, indicating a more complete block and therefore larger extent of septal injury 9. New-onset, persisting RBBB in

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particular has the highest 1-year mortality rates (73%) 5. A single-country study by Kleeman and co-authors was the first to suggest that RBBB was not independently associated with a worse outcome in non-ST elevation myocardial infarction (STEMI) 12. They speculated that RBBB in

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NSTEMI was an incidental finding that reflected chronic co-morbidities as opposed to a high-risk coronary insult seen in patients with STEMI. In contrast, our study demonstrates that RBBB

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across a range of ACS presentations, from unstable angina to STEMI, is a significant independent predictor of hospital mortality. There are several possible explanations for the higher in-hospital mortality among patients with RBBB in our study. First, RBBB is a high-risk marker of extensive coronary artery and/or left main disease reflected by our angiographic findings. In fact, those at highest risk of developing cardiogenic shock from MI and very high 1-year mortality frequently have left main coronary artery involvement 25. This contrasts other presentations of acute MI and RBBB that

ACCEPTED MANUSCRIPT 9 carry a better prognosis, such as inferior MI 10. Therefore, diffuse and left main coronary disease as opposed to more localized disease may suggest an acute on chronic process with a higher burden of underlying coronary artery disease.

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Second, our RBBB group received less optimal management than those with normal

conduction despite higher GRACE risk scores. Advanced age, more severe heart failure, higher creatinine levels, and multiple co-morbidities may have precluded invasive therapy. Similarities in

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less intensive therapy involving fibrinolysis and/or angioplasty were seen in previous trials 3,26. Another explanation for differences in management in our study relates to the lower rates of

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presenting ST elevation in the RBBB group. However, larger infarcts can still occur in the absence of typical ST elevation 8. Despite evolution and advancement of therapeutics over time, our results highlight that those with RBBB and ACS still receive suboptimal care. In fact, Widimsky and colleagues propose that new RBBB should be listed in future guidelines as a standard indication

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for early reperfusion therapy in the same way as new LBBB 8.

Finally, our patients with RBBB compared to no RBBB had higher rates of prior heart failure (15.5% vs. 9.2%, p<0.001) and more severe heart failure presentations (1.0% vs. 0.6%, for

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Killip Class IV, p<0.001) with compromised LVEF. In-hospital heart failure affected about a quarter of our patients presenting with RBBB (23.6% vs. 14.1%, p<0.001), which may be a

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mechanism to explain their higher short-term mortality. Studies indicate that heart failure complicating ACS is a poor prognostic factor persistent up to 4 years from index presentation 27,28. When we controlled for a prior history of heart failure, however, the prognostic value of RBBB in ACS at 6 months was attenuated. Future studies should investigate the utility of early recognition and aggressive interventions for this high-risk group in ACS. For example, Wong and colleagues noted a significant mortality benefit of fibrinolysis when ST-elevation resolution greater than 50% was

ACCEPTED MANUSCRIPT 10 identified within 60 minutes among patients presenting with RBBB 9. In patients with left coronary artery obstruction and cardiogenic shock, RBBB is a powerful independent predictor of short-term mortality 29. The benefit of emergency revascularization has previously been

also holds true for RBBB patients in the setting of acute MI.

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demonstrated in patients with cardiogenic shock 30. Future studies should evaluate whether this

Our study has several strengths compared to previous. We included a broad patient

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population with minimal exclusion criteria who presented with a heterogeneous spectrum of ACS, from UA to STEMI. In contrast, some of the previous studies had a relatively smaller and

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restricted number of patients in an era before modern pharmacological therapies and revascularization strategies. These studies also did not adjust for combined clinical variables from validated risk models. We were able to control for these predictors of mortality in our analysis and thereby provide a more robust assessment of the incremental prognostic value of RBBB in ACS.

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We incorporated a blinded, previously validated core lab for ECG interpretation to enhance the internal validity of our findings compared to ECG data gathered from local case report forms 19. On the other hand, our study was limited by a non-random sample of patients subject to

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potential non-consecutive patient enrollment and exclusion of early deaths. Our registries began enrolling patients more than a decade ago with differences in acute MI management presenting the

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possibility that our findings would be different in a more contemporary population receiving the latest therapies. However, since the majority of our patients with RBBB presented with NSTEACS, we would not expect early revascularization to significantly reduce in-hospital mortality. Furthermore, the proportion of patients undergoing coronary angiography may have been different between the groups with and without RBBB because the decision to intervene was left at the discretion of the interpreting physician. Limited by the lack of ECG data prior to presentation, we were also unable to ascertain whether RBBB was new, pre-existing, or dynamic. However, this is

ACCEPTED MANUSCRIPT 11 similar to real world practice where many patients presenting with ACS do not have previous ECGs available for comparison. We did not have prevalence data on non-ischemic conditions associated with RBBB including chronic obstructive pulmonary disease, interstitial lung disease,

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infiltrative cardiomyopathies, congenital heart disease, or pulmonary embolism. Six-month

follow-up vital status was not available for 10.9% of our participants, although the proportion lost to follow-up was similar between the groups with and without RBBB (p=0.32). The follow-up

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period was relatively short such that there might have been inadequate power to detect a significant prognostic association, despite our study being the one of the largest to date

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incorporating an ECG core lab. The upper limit of the 95% confidence interval of the adjusted odds ratio was 1.74, which could not exclude a clinically important higher 6-month mortality. In conclusion, RBBB on the presenting ECG may provide incremental prognostic value in ACS for in-hospital mortality beyond established GRACE risk score variables. This suggests that

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RBBB across a broad spectrum of ACS may require earlier and more intensive treatment to reduce

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adverse outcomes.

ACKNOWLEDGEMENTS

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We acknowledge all the study investigators, coordinators, and patients who participated in

the GRACE and Canadian ACS I registries. Our sincere thanks to Sue Francis, BA, for her assistance in the manuscript preparation. Dr. Shaun Goodman is supported by the Heart and Stroke Foundation of Ontario in his role as Heart and Stroke Foundation (Polo) Chair at the University of Toronto.

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28. Lewinter C, Torp-Pedersen C, Cleland JGF, Køber L. Right and left bundle branch block as predictors of long-term mortality following myocardial infarction. Eur J Heart Fail 2011;13:1349–1354.

ACCEPTED MANUSCRIPT 17 29. Sakakura K, Kubo N, Hashimoto S, Ikeda N, Funayama H, Hirahara T, Sugawara Y, Yasu T, Ako J, Kawakami M, Momomura S. Determinants of in-hospital death in left main coronary

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artery myocardial infarction complicated by cardiogenic shock. J Cardiol 2008;52:24–29. 30. Hochman JS, Sleeper LA, Webb JG, Sanborn TA, White HD, Talley JD, Buller CE, Jacobs AK, Slater JN, Col J, McKinlay SM, Picard MH, Menegus MA, Boland J, Dzavik V, Thompson CR,

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Wong SC, Steingart R, Forman R, Aylward PE, Godfrey E, Desvigne-Nickens P, LeJemtel TH. Early Revascularization in Acute Myocardial Infarction Complicated by Cardiogenic Shock. N

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Engl J Med 1999;341:625–634.

ACCEPTED MANUSCRIPT 18 FIGURE LEGENDS FIGURE 1: Angiographic findings in patients with and without Right Bundle Branch Block Angiographic results in patients with and without right bundle branch block (RBBB). RBBB had

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higher rates of ≥50% stenosis in any coronary artery, left main, and triple vessel disease.

Results were available for 4277 patients (181 with RBBB, 4096 without RBBB) from GRACE

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only (36% of the study cohort). Significant lesions were defined as ≥50% stenosis.

3VD, three vessel disease; LAD, left anterior descending; LCx, left circumflex; RCA, right

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circumflex artery.

Block

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FIGURE 2: Clinical outcomes (unadjusted) in patients with and without Right Bundle Branch

Clinical outcomes (unadjusted) for patients with and without right bundle branch block (RBBB).

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RBBB was associated with significantly higher rates of in-hospital heart failure as well as inhospital and 6-month mortality.

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*Data on in-hospital heart failure were available for 7449 (63%) of patients in GRACE.

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TABLE 1: Baseline patient characteristics of patients with and without Right Bundle Branch Block

NO (n=11,240)

YES (n=590)

P value

65 (55-74)

73 (65-80)

< 0.001

Men

66.8%

76.2%

< 0.001

Systemic hypertension

54.2%

61.9%

< 0.001

Dyslipidemia

45.3%

45.3%

0.99

23.3%

31.3%

< 0.001

30.0%

22.4%

< 0.001

55.9%

63.5%

< 0.001

30.7%

37.3%

0.001

9.2%

15.5%

< 0.001

Prior percutaneous coronary intervention

14.9%

16.7%

0.24

Prior coronary bypass graft surgery

11.1%

19.9%

< 0.001

Prior transient ischemic attack/stroke

7.5%

12.1%

< 0.001

Prior peripheral vascular disease**

9.0%

14.3%

0.001

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Age, (years)*

Diabetes mellitus Current smoker Prior angina pectoris

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Prior myocardial infarction Prior heart failure

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VARIABLES

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Right Bundle Branch Block

*Median (25th-75th percentiles) ** Data were available for 7470 (63%) participants

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TABLE 2: Clinical presentation of patients with and without Right Bundle Branch Block Right Bundle Branch Block NO (n=11,240) 142 (124-161)

Diastolic blood pressure, (mmHg)*

80 (70-91)

Heart rate, (beats/min)*

75 (63-88)

0.81

80 (68-90)

0.001

80 (65-94)

<0.001

82.7%

76.0%

Killip Class II

13.8%

18.1%

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Killip Class I

Killip Class III

P value

140 (124-164)

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Systolic blood pressure, (mmHg)*

YES (n=590)

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VARIABLES

<0.001

2.9%

4.9%

0.6%

1.0%

90 (79-106)

99 (83-127)

<0.001

41.8%

45.3%

0.10

Any T-wave inversion(≥2 contiguous leads)

27.7%

36.3%

<0.001

T-wave inversionin V1 and V2

8.6%

32.7%

<0.001

T-wave inversionin V2 and V3

8.4%

23.9%

<0.001

T-wave inversionin 2 adjacent precordial leads

19.3%

29.7%

<0.001

Q wave in V1 and V2

8.2%

11.5%

0.005

Q wave in ≥2 precordial leads

14.4%

23.4%

<0.001

ST deviation (≥0.5 mm)

78.7%

79.0%

0.86

Any ST depression (>0.5 mm)

53.2%

61.0%

<0.001

ST depression ≥0.5 mm in V1 and V2

5.5%

10.0%

<0.001

ST elevation ≥1 mm in ≥2 contiguous leads

34.6%

29.0%

0.005

Killip Class IV Creatinine, (µmol/L)*

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Elevated cardiac biomarkers

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ST elevation ≥1 mm in V1 and V2

4.8%

3.2%

0.081

Cardiac arrest

1.5%

3.8%

<0.001

128 (104-153)

143 (118-173)

<0.001

GRACE risk score*

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*Median (25th-75th percentiles)

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TABLE 3: In-hospital management of patients with and without Right Bundle Branch Block Right Bundle Branch Block RBBB (n=590)

P value

Fibrinolysis

19.5%

16.2%

0.047

Cardiac catheterization

51.3%

44.2%

0.001

Percutaneous coronary intervention

26.9%

22.1%

0.011

Coronary bypass graft surgery

3.9%

4.3%

0.63

Percutaneous coronary intervention and/or coronary bypass graft surgery

30.6%

26.4%

0.031

Left ventricular function * Normal

Moderately impaired Severely impaired

43.1%

24.3%

22.1%

17.3%

29.5%

2.2%

5.4%

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*Data available for 7031 (59%) study participants.

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56.2%

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Mildly impaired

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No RBBB (n=11,240)

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VARIABLES

< 0.001

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TABLE 4: Multivariable logistic regression analysis for in-hospital mortality Adjusted Odds Ratio

P value

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(95% CI) 2.12 (1.91-2.36)

<0.001

Heart rate (per 10 beats/min higher)

1.10 (1.05-1.15)

<0.001

Systolic blood pressure (per 10 mmHg higher)

0.85 (0.82-0.89)

<0.001

Creatinine (per 10 µmol/L higher)

1.03 (1.02-1.04)

<0.001

Elevated cardiac biomarkers

1.93 (1.55-2.42)

<0.001

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Age (per decade higher)

ST deviation

2.07 (1.44-2.96)

Killip class I

<0.001

Reference

Killip class II

2.06 (1.61-2.63)

<0.001

3.20 (2.22-4.63)

<0.001

5.26 (2.76-10.04)

<0.001

Cardiac arrest at presentation

4.82 (2.99-7.77)

<0.001

Right bundle branch block

1.45 (1.02-2.07)

0.039

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Killip class IV

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Killip class III

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TABLE 5: Multivariable logistic regression analysis for 6-month mortality Adjusted Odds Ratio

P value

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(95% CI) 2.01 (1.85-2.18)

<0.001

Prior myocardial infarction

1.00 (0.84-1.21)

0.97

1.46 (1.16 – 1.83)

0.001

Prior heart failure

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Age (per decade higher)

1.13 (1.09-1.17)

<0.001

Systolic blood pressure(per 10 mmHg higher)

0.89 (0.87 -0.92)

<0.001

Creatinine (per 10 µmol/L higher) Elevated cardiac biomarker ST deviation Killip class I

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Heart rate (per 10 beats/min higher)

1.04 (1.03-1.05)

<0.001

1.63 (1.38-1.94)

<0.001

1.94 (1.49-2.51)

<0.001

Reference

Killip class II

<0.001

2.56 (1.86-3.53)

<0.001

3.94 (2.12-7.30)

<0.001

Cardiac arrest at presentation

3.21 (2.04-5.05)

<0.001

Right bundle branch block

1.29 (0.95-1.74)

0.098

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1.76 (1.44-2.16)

Killip class III

AC C

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Killip class IV

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FIGURE 1: Angiographic findings in patients with and without RBBB

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FIGURE 2: Clinical outcomes (unadjusted) in patients with and without RBBB