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Updated: Jun 27, 2026

Benefits of Cardiac Resynchronization Therapy in an Asynchronous Heart Failure Model Induced by Left Bundle Branch Ablation and Rapid Pacing
Published on: December 11, 2017
[Left bundle branch block in alternate beats during fast-slow atrioventricular nodal reentrant tachycardia]
Aldo Merlino1, Mario Soccorso Iudicello, Giuseppe Di Stefano
1Divisione di Cardiologia, Presidio Ospedaliero S. Agata Militello, ASL 5, Messina. meral@tiscali.it
Abstract:
The presented ECG shows a fast-slow atrioventricular nodal reentrant tachycardia with regular alternation of narrow and wide beats. The wide QRS complexes have a typical configuration of left bundle branch block. Alternation of narrow and wide beats during supraventricular tachycardia is an uncommon finding. It can be due to several mechanisms. The analysis of the ECG demonstrates that the bundle branch block is tachycardia-dependent or phase 3. Supernormal left bundle branch conduction associated with a retrograde concealed conduction into the anterogradely blocked bundle branch helps explain this phenomenon.
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