title: [Left bundle branch block in alternate beats during fast-slow atrioventricular nodal reentrant tachycardia].
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.
authors.affiliation: Divisione di Cardiologia, Presidio Ospedaliero S. Agata Militello, ASL 5, Messina. meral@tiscali.it
authors.forename: Aldo
authors.initials: A
authors.lastname: Merlino
authors.forename: Mario Soccorso
authors.initials: MS
authors.lastname: Iudicello
authors.forename: Giuseppe
authors.initials: G
authors.lastname: Di Stefano
mesh_terms: D000368:Aged; D002037:Bundle-Branch Block / Q000150:complications* / Q000503:physiopathology*; D004562:Electrocardiography; D005260:Female; D006801:Humans; D013611:Tachycardia, Atrioventricular Nodal Reentry / Q000150:complications* / Q000503:physiopathology*