Clinical Research
Coronary Artery Disease
Right, But Not Left, Bundle Branch Block Is Associated With Large Anteroseptal Scar

https://doi.org/10.1016/j.jacc.2013.04.060Get rights and content
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Objectives

This study sought to test the hypothesis that right bundle branch block (RBBB) patients have larger scar size than left bundle branch block (LBBB) patients do.

Background

A proximal septal perforating branch of the left anterior descending (LAD) coronary artery most commonly perfuses the right bundle branch and left anterior fascicle, but not the left posterior fascicle. Thus, proximal LAD occlusions should cause RBBB, not LBBB.

Methods

We performed electrocardiograms and magnetic resonance imaging for scar quantification in 233 patients with left ventricular (LV) ejection fraction ≤35% who were receiving primary prevention implantable cardioverter-defibrillators (ICD cohort). Scar size and location were compared among patients with RBBB, LBBB, nonspecific LV conduction delay, and QRS <120 ms. A second cohort of 20 hypertrophic cardiomyopathy patients undergoing alcohol septal ablation was studied to determine whether controlled infarction in a proximal LAD septal perforator caused RBBB or LBBB.

Results

In the ICD cohort, LV ejection fraction was similar between RBBB and LBBB patients (24.9% vs. 25.0%; p = 0.98); however, RBBB patients had significantly larger scar size (24.0% vs. 6.5%; p < 0.0001). Patients with nonspecific LV conduction delay or QRS <120 ms had intermediate scar size (12.9% and 14.4%, respectively). Those with RBBB (compared with LBBB) were more likely to have ischemic heart disease (79% vs. 29%; p < 0.0001). In the alcohol septal ablation cohort, 15 of 20 patients (75%) developed RBBB, but no patients developed LBBB.

Conclusions

In patients with LV ejection fraction ≤35%, RBBB is associated with significantly larger scar size than LBBB is, and occlusion of a proximal LAD septal perforator causes RBBB. In contrast, LBBB is most commonly caused by nonischemic pathologies.

Key Words

ischemic heart disease
left bundle branch block
myocardial infarction
nonischemic cardiomyopathy
right bundle branch block

Abbreviations and Acronyms

CMR-LGE
cardiac magnetic resonance late gadolinium enhancement
CRT
cardiac resynchronization therapy
ECG
electrocardiography/electrocardiogram(s)
ICD
implantable cardioverter-defibrillator
LAD
left anterior descending coronary artery
LV
left ventricle/ventricular
LVCD
left ventricular conduction delay
LBBB
left bundle branch block
MI
myocardial infarction(s)
RBBB
right bundle branch block
RCA
right coronary artery

Cited by (0)

The mention of commercial products, their sources, or their use in connection with material reported herein is not to be construed as either an actual or implied endorsement of such products by the U.S. Department of Health and Human Services. This project was supported in part by the U.S. Food and Drug Administration's Critical Path Initiative; Donald W. Reynolds Cardiovascular Research Center at Johns Hopkins University; and the National Heart, Lung, and Blood Institute, National Institutes of Health (#HL103812 to Dr. Wu, #HL91062 to Dr. Tomaselli, and #HL61912 to Dr. Selvester). Use of the custom research software tool, Cinetool, was obtained through a research agreement between Dr. Wu and GE Healthcare. Dr. Wu has received modest royalties for the licensing rights to use the gray zone methodology described in this paper. All other authors have reported that they have no relationships relevant to the contents of this paper to disclose.