Sustained bundle branch reentry as a mechanism of clinical tachycardia.

Abstract

The incidence of sustained bundle branch reentrant (BBR) tachycardia as a clinical or induced arrhythmia or both continues to be underreported. At our institution, BBR has been the underlying mechanism of sustained monomorphic ventricular tachycardia in approximately 6% of patients, whereas mechanisms unrelated to BBR were the cause in the rest. Data gathered from 20 consecutive patients showed electrophysiologic characteristics that suggest this possibility. These include induction of sustained monomorphic tachycardia with typical left or right bundle branch block morphology or both and atrioventricular dissociation or ventriculoatrial block. On intracardiac electrograms, all previously published criteria for BBR were fulfilled, and in addition, whenever there was a change in the cycle length of tachycardia, the His to His cycle length variation produced similar changes in ventricular activation during subsequent complexes with no relation to the preceding ventricular activation cycles. Compared with patients with ventricular tachycardia due to mechanisms unrelated to BBR, patients with BBR had frequent combination of nonspecific intraventricular conduction defects and prolonged HV intervals (100% vs. 11%, p <0.001). When this combination was associated with a tachycardia showing a left bundle branch block pattern, BBR accounted for the majority compared with mechanisms unrelated to BBR (73% vs. 27%, p< 0.01). The above finding in patients with dilated cardiomyopathy should raise the suspicion of sustained BBR because dilated cardiomyopathy was observed in 95% of the patients with BBR. Twelve of the 20 patients were treated with antiarrhythmic agents, and the other eight were managed by selective catheter ablation of the right bundle branch with electrical energy. Our data suggest that sustained BBR is not an uncommon mechanism of tachycardia; it can be induced readily in the laboratory and is amenable to catheter ablation by the very nature of its circuit. The clinical and electrophysiologic features outlined in this study should enable one to correctly diagnose this important arrhythmia. (Circulation 1989;79:256-270) M acroreentry within the His-Purkinje system commonly referred to as bundle branch reentry (BBR) is a frequently observed phenomenon in the laboratory.1-3Although scattered cases of sustained BBR tachycardia have been reported, no large series dealing with this phenomenon exists in the literature.4-11 The incidence of BBR as a mechanism of sustained ventricular tachycardia (VT), therefore, continues to be underreported in the literature, and consequently, there is less awareness of sustained BBR tachycardia as a significant clinical arrhythmia.

Bundle-Branch Reentry and the Postpacing Interval After Entrainment by Right Ventricular Apex Stimulation

“…Particular attention was paid to recording the His bundle electrogram during tachycardia 3 or to entrain the tachycardia by atrial pacing 6 to confirm or exclude a BBR mechanism. When necessary, additional catheters, such as a decapolar catheter with short interelectrode distance 7 or a steerable catheter, were introduced to record the His bundle electrogram, a bundle-branch electrogram, or both.…”

“…MR-VT diagnosis was established when BBR was ruled out as the reentrant VT mechanism. 3,4 BBR-VT diagnosis was established according to previously published criteria (criteria A) [2][3][4]6 : (1) QRS-complex morphology with typical BBB pattern consistent with ventricular depolarization through the appropriate bundle branch; (2) AV dissociation during tachycardia; (3) exclusion of a tachycardia from supraventricular origin by established criteria; (4) prolonged HV interval during sinus rhythm; (5) a stable His or bundle-branch electrogram preceding each ventricular activation during tachycardia with an HV interval longer than, equal to, or Ͻ10 ms shorter than that recorded during sinus rhythm; and (6) spontaneous changes in the bundle potential CL preceding similar changes in the ventricular CL. Because BBR has been found to be the tachycardia mechanism despite criterion 6 not being demonstrated, 5,8 BBR-VT diagnosis was also established when all the following criteria (criteria B) were fulfilled: (1) all 6 criteria A were fulfilled except for criterion 6, that is, spontaneous changes in the bundle potential CL followed rather than preceded similar changes in the ventricular CL; (2) Ն1 additional BBR-VT morphologies were also inducible and fulfilled all criteria A; (3) the difference in tachycardia CL was Յ30 ms compared with those of the other induced BBR-VTs; (4) no MR-VT, either sustained or nonsustained, was inducible; (5) the patient had no structural heart disease; and (6) the inducibility of all tachycardias was suppressed after bundle-branch ablation.…”

“…Therefore, some VTs failing to show these responses in the present and other 3,4 studies could have been included in the MR-VT group despite having a BBR mechanism. BBR is highly unlikely in the absence of significant His-Purkinje disease, [3][4][5] however, and except for 10 MR-VT patients, none showed prolonged QRS complex (Ͼ120 ms) or HV interval (Ͼ60 ms) during sinus rhythm in the present study.…”

“…1,2 Recognition or exclusion of BBR, however, can be challenging and timeconsuming. [3][4][5][6] Criteria based on the recording of the His bundle electrogram have several limitations, such as failure to record the His bundle electrogram during tachycardia because of catheter displacement or severe His-Purkinje disease, [3][4][5][6][7] and BBR nonrecognition when oscillations in the VV interval precede those of the HH interval because of conduction variations in the antegrade, rather than the retrograde, conducting bundle branch. 6,8 More recently, demonstration of both orthodromic concealed fusion (concealed fusion with tachycardia QRS-complex morphology preservation) and manifest fusion during entrainment by atrial and ventricular pacing, respectively, has been proposed as an alternative approach to BBR diagnosis.…”

“…9,10 We postulated ( Figure 1) that BBR-VT entrainment pacing from the right ventricular apex (RVA) should result in a PPI similar to the tachycardia CL (TCL) because the right bundle-branch distal insertion is in this anatomic area. This approach may differentiate BBR from other mechanisms of wide-QRS-complex tachycardia with AV dissociation, 3,11 such as ventricular myocardial reentry (MR) or AV nodal reentry (AVNR), where the circuit is usually away from the RVA.…”