Differential diagnosis of tachycardia with a typical left bundle branch block morphology

Figure 3 Atrial tachycardia can result in functional left bundle branch block. A reentrant circuit in the left atrium results in tachycardia that rapidly conducts to the ventricle via the atrioventricular node. Rate-dependent conduction block occurs in the left bundle branch. Adapted from[10], by permission of Oxford University Press, Inc. LBB: Left bundle branch; RBB: Right bundle branch.