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Published on: April 25, 2014
Outcomes in patients with chronicity of left bundle-branch block with possible acute myocardial infarction
Michael C Kontos1, Hammad A Aziz, Vinh Q Chau
1Division of Cardiology, Department of Internal Medicine, Virginia Commonwealth University, Richmond, USA. mkontos@mcvh-vcu.edu
Insights
New or presumed new left bundle-branch block (LBBB) in emergency department patients does not reliably indicate myocardial infarction (MI). Concordant ST changes on ECG are key predictors of MI and mortality, suggesting current reperfusion guidelines for LBBB may need revision.
Area of Science:
- Cardiology
- Emergency Medicine
- Electrocardiography
Background:
- Current guidelines recommend rapid reperfusion for emergency department (ED) patients with likely myocardial infarction (MI) and new left bundle-branch block (LBBB).
- The applicability of these guidelines to lower-risk ED patients with LBBB remains uncertain.
- Left bundle-branch block is a critical ECG finding that requires careful interpretation in the context of suspected MI.
Purpose of the Study:
- To investigate the diagnostic value of new or presumably new left bundle-branch block (LBBB) in emergency department patients with suspected myocardial infarction (MI).
- To identify electrocardiogram (ECG) findings that predict MI and mortality in patients with LBBB.
- To evaluate the current guidelines for reperfusion therapy in this patient population.
Main Methods:
- A cohort of 401 consecutive patients undergoing an MI rule-out protocol with LBBB was analyzed.
- Left bundle-branch blocks were categorized as chronic, new, or presumably new based on prior ECG availability.
- Concordant ST elevation or depression (≥1 mm) was assessed, and rates of MI, peak MB values, and 30-day mortality were compared across groups.
Main Results:
- A majority of patients (64%) presented with new (37%) or presumably new LBBB (27%).
- Myocardial infarction (MI) was diagnosed in 29% of patients, with no significant difference in prevalence or size across LBBB groups (chronic, new, presumably new).
- Concordant ST changes were highly predictive of MI (OR 17) and mortality (OR 4.3), while new/presumably new LBBB was not.
Conclusions:
- Most emergency department patients with possible MI and new or presumably new LBBB do not have an MI.
- Concordant ST changes on ECG are a crucial predictor of MI and adverse outcomes in patients with LBBB.
- Current guidelines for early reperfusion therapy in LBBB patients warrant reconsideration based on these findings.
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 < .01). Peak MB was >5× 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 < .001) and an independent predictor of mortality (odds ratio 4.3, 95% CI 1.3-15, P < .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.
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