title: Conduction disorders in bradyasystolic out-of-hospital cardiac arrest.
abstract: Bradyasystolic heart rhythms are often recorded in out-of-hospital cardiac arrest (OHCA). Atrioventricular (AV) conduction disorders might lead to OHCA, but the prevalence of AV-conduction disorders and other bradyasystolic rhythms in OHCA is unknown. These patients might benefit from pre-hospital pacing. We aimed to determine the prevalence of different types of bradyasystolic heart rhythms in OHCA, including third degree AV-block, and document survival rates.
  
  
  
  We used data from the ARREST-registry of OHCA in the Netherlands. Patients with bradyasystolic OHCA in 2006-2012 were included. ECGs were classified according to the presence of P-waves and QRS complexes in five rhythm groups. Differences in survival to discharge in relation to resuscitation characteristics, rhythm and pacing were tested using Chi-Square test and multivariate regression analysis.
  
  
  
  We included 2333 patients with a bradyasystolic rhythm; 371 patients (16%) presented with a third degree AV-block. In total 45 patients (1.9%, 95%-CI 1.4-2.5%) survived. A third degree AV-block (adjusted OR 0.86, 95%-CI 0.38-1.96) or pacing (adjusted OR 0.89, 95%-CI 0.21-3.78) was not associated with survival. Pacing was initiated in 110 patients (4.7%), after a long delay (median 18.7min). The strongest association with survival was found for the presence of a bradycardia (vs. asystole) (adjusted OR 4.20, 95%-CI 1.79-9.83), bystander witnessed (OR 4.13, 95%-CI 1.45-11.8) and EMS witnessed collapse (OR 5.18, 95%-CI 2.77-9.67).
  
  
  
  In bradyasystolic OHCA, 16% of all patients present with third degree AV-block, but survival for these and other bradyasystolic patients remains poor. Pacing is seldom initiated, often delayed, and rarely beneficial.
authors.affiliation: Academic Medical Center - Department of Cardiology, Meibergdreef 9, 1105 AZ Amsterdam, The Netherlands. Electronic address: m.hulleman@amc.nl.
authors.forename: Michiel
authors.initials: M
authors.lastname: Hulleman
authors.affiliation: Academic Medical Center - Department of Cardiology, Meibergdreef 9, 1105 AZ Amsterdam, The Netherlands.
authors.forename: Hanne
authors.initials: H
authors.lastname: Mes
authors.affiliation: Academic Medical Center - Department of Cardiology, Meibergdreef 9, 1105 AZ Amsterdam, The Netherlands.
authors.forename: Marieke T
authors.initials: MT
authors.lastname: Blom
authors.affiliation: Academic Medical Center - Department of Cardiology, Meibergdreef 9, 1105 AZ Amsterdam, The Netherlands.
authors.forename: Rudolph W
authors.initials: RW
authors.lastname: Koster
mesh_terms: D000368:Aged; D000369:Aged, 80 and over; D054537:Atrioventricular Block / Q000401:mortality*; D001919:Bradycardia / Q000401:mortality*; D016887:Cardiopulmonary Resuscitation / Q000706:statistics & numerical data*; D016009:Chi-Square Distribution; D004562:Electrocardiography; D004632:Emergency Medical Services; D005260:Female; D006329:Heart Conduction System / Q000503:physiopathology*; D006801:Humans; D008297:Male; D008875:Middle Aged; D058687:Out-of-Hospital Cardiac Arrest / Q000401:mortality*; D011446:Prospective Studies; D012042:Registries; D012044:Regression Analysis
keywords: AV-conduction disorders; Asystole; Bradyasystole; Bradycardia; Cardiac arrest; Cardiopulmonary resuscitation; Pulseless electrical activity; Transcutaneous pacing