title: Phase 4 paroxysmal AV block in a patient with scleroderma.
abstract: A 72-year-old man with limited cutaneous systemic scleroderma was hospitalized for two episodes of witnessed syncope. The baseline 12-lead electrocardiogram was normal but on telemetry there were numerous episodes of paroxysmal AV block with asystolic periods of up to 7.5 s duration. Analysis of the rhythm strips revealed phase 4 intra-His bundle block characterized by critical P-P intervals that triggered the AV block, and a narrow range of junctional escape to subsequent P wave intervals that were required to release the AV block. A dual chamber pacemaker was implanted.
authors.affiliation: Department of Internal Medicine, Carolinas Medical Center, Charlotte, NC, USA.
authors.forename: Ross
authors.initials: R
authors.lastname: Butschek
authors.forename: Brian D
authors.initials: BD
authors.lastname: Powell
authors.forename: Laszlo
authors.initials: L
authors.lastname: Littmann
mesh_terms: D000368:Aged; D054537:Atrioventricular Block / Q000175:diagnosis* / Q000209:etiology / Q000517:prevention & control*; D058409:Cardiac Resynchronization Therapy Devices; D003937:Diagnosis, Differential; D006801:Humans; D008297:Male; D012595:Scleroderma, Systemic / Q000150:complications / Q000175:diagnosis* / Q000628:therapy*; D016896:Treatment Outcome
keywords: Bradycardia-dependent AV block; CREST; Intra-His bundle block; Paroxysmal AV block; Phase 3 block; Phase 4 block; Progressive systemic sclerosis