Prevalence of acute myocardial infarction in patients with presumably new
left bundle-branch block
Nilay Mehta, DO,
Henry D. Huang, MD,
Salman Bandeali, MD,
James M. Wilson, MD,
Yochai Birnbaum, MD
Division of Cardiology, University of Texas Medical Branch, Galveston, TX
Section of Cardiology, Baylor College of Medicine, Houston, TX
Department of Medicine, Baylor College of Medicine, Houston, TX
Department of Cardiology, the Texas Heart Institute at St. Luke's Episcopal Hospital, Houston, TX
Received 27 January 2012
Abstract Objectives: We assessed the prevalence of true acute myocardial infarction and the need for
emergent revascularization among patients with new or presumably new left bundle branch block
(nLBBB) for whom the primary percutaneous coronary intervention protocol was activated.
Methods and Results: Among 802 patients, 69 (8.6%) had nLBBB. The chief presenting symptom
was chest pain or cardiac arrest in 36 patients (52.2%) and shortness of breath in 15 (21.7%). Less
than 30% of the patients had elevated cardiac troponin-I, and less than 10% had elevated creatine
kinase–MB. Only 11.6% of the patients underwent emergent revascularization; the rate was higher
for patients who presented with chest pain or cardiac arrest or shortness of breath than for patients
who presented with other symptoms.
Conclusions: Acute myocardial infarction and the need for emergent revascularization are relatively
uncommon among patients who present with nLBBB, especially when symptoms are atypical.
Current guidelines for primary percutaneous coronary intervention protocol activation for nLBBB
should be reconsidered.
© 2012 Elsevier Inc. All rights reserved.
Keywords: Left bundle branch block; Acute myocardial infarction; Electrocardiogram; Primary percutaneous coronary
According to the American College of Cardiology and
American Heart Association (ACC/AHA) guidelines, in the
absence of contraindications, reperfusion therapy should be
administered to patients with symptoms compatible with
ST-segment elevation myocardial infarction (STEMI) if
these symptoms arose within the prior 12 hours and if an
electrocardiogram (ECG) shows new or presumably new
left bundle branch block (nLBBB) (level of evidence A).
These recommendations stemmed from the Fibrinolytic
Therapy Trialists' review of major randomized trials of
ﬁbrinolysis versus placebo,
which suggested that patients
with a bundle branch block had higher baseline mortality
and had the greatest incremental improvement in survival
when given ﬁbrinolytics. However, in this meta-analysis,
right and left bundle branch block were not analyzed
separately, nor were known LBBB and nLBBB. Two
studies have found that the prognosis of patients with acute
myocardial infarction (AMI) and right bundle branch block
(especially those with anterior STEMI) is worse than that
of patients with LBBB.
Subsequent analyses by Shlipak
concluded that treating all patients
who have suspected AMI and who present with LBBB
(whether it is new or known) with ﬁbrinolytics is preferable
to using ECG criteria to diagnose AMI or to determine the
age of LBBB.
In 1996, Sgarbossa et al evaluated the ECGs of more than
26, 000 patients in the GUSTO-I (Global Utilization of
Streptokinase and Tissue Plasminogen Activator for Oc-
cluded Coronary Arteries) trial and determined that an AMI
could be diagnosed by using 3 ECG criteria in patients with
known or new LBBB: ST-segment elevation (STE) of ≥1
mm that is concordant with the QRS complex; ST-segment
depression of ≥1 mm in lead V
; and STE of ≥5
Available online at www.sciencedirect.com
Journal of Electrocardiology 45 (2012) 361 – 367
Financial support: None.
Corresponding author. One Baylor Plaza, MS: BCM 620, Suite 9.32,
Houston, TX 77030.
E-mail address: firstname.lastname@example.org
The ﬁst two authors equally contributed to the manuscript.
0022-0736/$ – see front matter © 2012 Elsevier Inc. All rights reserved.