Episode-level characteristics of atrial fibrillation are associated with symptomatic events

Abstract Background Symptoms related to Atrial Fibrillation (AF) can be debilitating are the main driver to seek hospital attention. However, many patients do not experience any symptoms and intra-subject variation is also seen. The reasons for this variability are unclear and a better understanding of the features associated with symptomatic AF episodes may improve stratification and personalisation of care. Purpose To evaluate the features associated with symptomatic versus asymptomatic AF episodes recorded using an insertable cardiac monitor (ICM). Methods We linked a deidentified database of aggregated electronic health records from 2007-2021 to a manufacturer’s device data warehouse with continuous diagnostic monitoring data. ICM-detected AF episodes of a minimum of one hour duration were retrospectively analysed. Symptomatic AF was defined as episodes temporally correlated with patient activation of a handheld symptom activator device. Episode- level comparison of mean heart rate at detection and during the entire AF episode, AF episode duration, activity index and AF evidence score (a linear scale based on episode irregularity) between symptomatic and asymptomatic patients was performed. Data was reported as mean ± standard deviation or median (inter-quartile range) if non-normally distributed. Wilcoxon Signed-Rank test was used for per-subject paired analysis. Multi-variate logistic regression model with binomial distribution and exchangeable correlation structure was used to identify factors associated with symptomatic episodes. A Generalized Estimating Equations model was used to account for multiple AF episodes within a subject. Results 417,432 unique episodes were recorded in 11,436 patients. 6,190 (1.48%) episodes from 1776 patients were marked as symptomatic. These were longer (5.5 (12.1) hours vs 3.7 (9.3) hours), had a higher mean HR at onset (105.7±29.3bpm vs 89.1+-24.6bpm) and a greater AF evidence score (97.6+-26.9 vs 82.1+-24.4). On multi- variate logistic regression, AF evidence score, and mean HR was independently associated with symptomatic AF (table 1). Per subject analysis of 1589 patients with both symptomatic and asymptomatic episodes also suggested significantly higher AF evidence scores. (-3.64±22.0). Discussion: This is the largest episode-level characterisation of AF episodes in patients with an ICM. The AF evidence score, a marker of ventricular rate variability, may be useful for the remote stratification of AF episodes. Prospective study of stratification based on this parameter would be of value.Regression model of symptomatic AF