Conduction disorders in bradyasystolic out-of-hospital cardiac arrest

AIMS: 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. METHODS: 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. RESULTS: 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). CONCLUSION: 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.