Bundle branch reentrant ventricular tachycardia

Abstract

Bundle branch reentrant (BBR) tachycardia is an uncommon form of ventricular tachycardia (VT) incorporating both bundle branches into the reentry circuit. The arrhythmia is usually seen in patients with an acquired heart disease and significant conduction system impairment, although patients with structurally normal heart have been described. Surface ECG in sinus rhythm (SR) characteristically shows intraventricular conduction defects. Patients typically present with presyncope, syncope or sudden death because of VT with fast rates frequently above 200 beats per minute. The QRS morphology during VT is a typical bundle branch block pattern, usually left bundle branch block, and may be identical to that in SR. Prolonged His-ventricular (H-V) interval in SR is found in the majority of patients with BBR VT, although some patients may have the H-V interval within normal limits. The diagnosis of BBR VT is based on electrophysiological findings and pacing maneuvers that prove participation of the His- Purkinje system in the tachycardia mechanism. Radiofrequency catheter ablation of a bundle branch can cure BBR VT and is currently regarded as the first line therapy. The technique of choice is ablation of the right bundle. The reported incidence of clinically significant conduction system impairment requiring implantation of a permanent pacemaker varies from 0% to 30%. Long-term outcome depends on the underlying cardiac disease. Patients with poor systolic left ventricular function are at risk of sudden death or death from progressive heart failure despite successful BBR VT ablation and should be considered for an implantable cardiovertor-defibrillator.

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.

Figure 2

Twelve-lead ECG during a spontaneous episode of bundle branch reentrant tachycardia (A). Surface ECG leads I, II, III, V1, V2, V6 (B) or II, III, V1 (C) and intracardiac recordings from the His bundle (His) and right ventricular apex (RVA) during bundle branch reentrant tachycardia induced in the same patient. The recordings show many characteristic diagnostic features of bundle branch reentrant tachycardia: (1) typical LBBB morphology and left superior axis (A); (2) AV dissociation (C); (3) H preceding every V with the HV interval (112 ms) greater than that recorded during sinus rhythm (68 ms) (B and C); (5) H precedes the right bundle deflection. This sequence is consistent with ventricular activation through the right bundle branch and is appropriate for a LBBB morphology of tachycardia (B); (6) spontaneous changes in the HH intervals preceded similar changes in the VV intervals (C); and (7) spontaneous termination of tachycardia with retrograde conduction block to H (C). A, H, RB, and V denote atrial, His bundle, right bundle, and ventricular electrograms, respectively. (From: Mazur A, Iakobishvili Z, Kusniec J, Strasberg B. Bundle branch reentrant ventricular tachycardia in a patient with the Brugada electrocardiographic pattern. A.N.E. 2003;8:252-255, with permission of Blackwell Futura Publishing, Inc.)

Figure 3

Surface ECG leads I, II, III, and intracardiac recordings from the left bundle (LB), His bundle (HBE), and right atrium (RA) during sinus rhythm (A) and interfascicular reentrant tachycardia (B). Note characteristic features of interfascicular reentry: (1) the H-V interval during tachycardia (70 ms) is shorter than that in sinus rhythm (100 ms); and (2) the LB potential precedes the His bundle potential. See text for discussion. (From: Crijns HJ, Smeets JL, Rodriguez LM, et al. Cure of interfascicular reentrant ventricular tachycardia by ablation of the anterior fascicle of the left bundle branch. J Cardiovasc Electrophysiol 1995;6:486-492, with permission of Blackwell Futura Publishing, Inc.)