Characterising RR Intervals in Atrial Fibrillation Detected Through Screening

Atrial fibrillation (AF) is known to be characterised by increased RR interval variability. However, the characteristics of RR intervals in AF detected through screening have not been extensively studied. The aim of this study was to characterise RR intervals in AF detected in screening of older, community dwelling adults. RR interval characteristics were extracted from 2, 709 ECGs from the SAFER AF Screening Programme, consisting of 671 ECGs exhibiting AF, and 2,038 non-AF ECGs. The characteristics included measures of the mean RR interval, the variability in RR intervals, and the proportion of successive RR intervals differing by at least 50ms (pNN50). All characteristics differed significantly between AF and non-AF ECGs. pNN50 provided the highest performance for discriminating between AF and non-AF, with an AUROC of 96%. In AF the majority of successive RR intervals differed by more than 50ms, although there was large variation in the level of RR interval variability between AF ECGs. This study contributes to furthering our understanding of RR interval characteristics in AF. In the future this could form the basis of an algorithm to automatically identify ECGs exhibiting AF with potential applications in AF screening.