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. 2005 Apr 1;5(2):86–95.

Figure 1.

Figure 1

Scheme of bundle branch (A) and interfascicular (B) reentry. (A) Antegrade conduction is over the right bundle (RB) and retrograde conduction is up the left bundle (LB). Because ventricular activation (V) starts at the right ventricular apex, the QRS morphology is a typical LBBB. Reversal of the reentry circuit with activation of the ventricles through the left bundle system is associated with a typical RBBB QRS morphology. Note that retrograde activation of the His bundle (H) occurs during antegrade activation of the RB. See text for discussion. (B) Antegrade conduction proceeds over the anterior fascicle (LAF) and retrograde conduction up the posterior fascicle (LPF). Because ventricles are activated through the left bundle system, the QRS morphology has a RBBB pattern. In this type of the circuit, activation of the ventricles occurs over the LAF and is associated with a left anterior fascicular block pattern. Reversal of the reentry circuit with activation of the ventricles over the LPF shows a left posterior fascicular block pattern. Note that the LB and H are activated retrogradely during antegrade activation of the LAF. See text for discussion.