title: Bundle branch block in alternate beats during 2:1 atrial flutter.
abstract: This presentation deals with a case of atrial flutter. During 2:1 A/V conduction, the QRS complexes showed a regular alternation of narrow beats and wide beats with a typical configuration of left bundle branch block. In contrast, pauses resulting from 4:1 A/V conduction ratio always resulted in narrow beats. Disappearance of left bundle branch block with long R-R intervals demonstrated that the block was tachycardia-dependent or phase 3. Analysis of the tracing suggested that narrowing of QRS complexes in alternate beats was due to supernormal left bundle branch conduction associated with retrograde concealed conduction into the anterogradely blocked bundle branch.
authors.affiliation: Department of Cardiology, University of Messina, Italy.
authors.forename: Francesco
authors.initials: F
authors.lastname: Luzza
authors.forename: Maria Pia
authors.initials: MP
authors.lastname: Calabrò
authors.forename: Scipione
authors.initials: S
authors.lastname: Carerj
authors.forename: Giuseppe
authors.initials: G
authors.lastname: Oreto
mesh_terms: D000368:Aged; D001282:Atrial Flutter / Q000175:diagnosis*; D002037:Bundle-Branch Block / Q000175:diagnosis*; D004562:Electrocardiography; D005260:Female; D006801:Humans