BUNDLE-BRANCH REENTRY VENTRICULAR-TACHYCARDIA WITH 2 DISTINCT LEFT-BUNDLE-BRANCH BLOCK MORPHOLOGIES

Introduction: Bundle branch reentry ventricular tachycardia (VT) is us ually amenable to treatment with radiofrequency ablation, Different QR S morphologies during VT are possible when anterograde ventricular act ivation is over the left bundle branch, Manifestations of this reentra nt tachycardia with more than one QRS morphology with anterograde acti vation via the right bundle have not been reported and would be unusua l due to the more discrete anatomy of the right bundle branch, Methods and Results: An electrophysiologic study was conducted in a patient w ith dilated ventricle and diminished ventricular function with VT, Typ ical characteristics of bundle branch reentry were noted when VT was i nduced, The study was notable for the presence of a right bundle recor ding only during macroreentrant beats or VT and the distal location of the recording, Radiofrequency ablation was performed. Postablation st imulation again induced VT, proven to be of the same bundle branch ree ntry mechanism but of a different QRS morphology, A second ablation ma s required for complete ablation of this patient's bundle branch reent ry VT. Conclusion: In bundle branch reentry utilizing the left bundle as the retrograde limb and the right bundle branch as the anterograde limb of the circuit, VT of more than one distinct morphology can be se en, Careful evaluation to assess for the persistence of VT of the same mechanism is necessary to ensure complete ablation of the reentrant c ircuit, Preexisting right bundle disease and a dilated heart with more dispersed distal right bundle branches may predispose to such a pheno menon.