Atrial fibrillation and cardioversion in the critically ill – a post-hoc analysis of emergency department patients

Abstract

Objective: In critically ill patients with atrial fibrillation (AF) standard treatment algorithms might not be applicable. Emergency departments (ED) play a crucial role in implementing individualized treatment approaches. The aim of this study was to evaluate the effectiveness of ED cardioversion algorithms based on lactate levels as a surrogate for severity of illness. Design, Setting and Patients: This retrospective study was conducted at the ED of the Medical University of Vienna, Austria, between 2012 and 2022. A consecutive series of 3,535 AF episodes were analyzed. Measurement and main results: The main outcome was cardioversion success depending on serum lactate levels [mmol/L]. Lactate levels were divided into quintiles (lac <1.1, 1.1 - 1.3, 1.4 - 1.7, 1.8 - 2.3 and > 2.3mmol/L) and into two groups using a cut-off of 4mmol/L. Overall CV success decreased with rising lactate levels (79% in lac < 1.1mmol/L vs. 61% in lac > 2.3mmol/L; p < 0.001). For electrical cardioversion [eCV] (n=1,119 cases; sinus rhythm [SR] achieved in 86%) success, no significant difference was seen in relation to lactate levels. However, for medical cardioversion [mCV] (n=759; 67% SR), conversion success decreased with increasing lactate levels (SR: lac < 1.1mmol/L 84% vs. lac > 2.3mmol/L 59%; p < 0.001). Conclusion: Overall cardioversion success was less likely with rising lactate levels; especially medical cardioversion success rates decreased. Therefore, AF in the critically ill may benefit from either electrical cardioversion, treatment of the underlying condition or primary rate control, rather than medical cardioversion attempts.