Identification of atrial complex electrograms by short-coupled extrastimuli in paroxysmal and persistent atrial fibrillation

Type of funding sources: Public hospital(s). Main funding source(s): - Health Council of the Andalusian Regional Government through the project "PI-0057-2017".

- European Regional Development Fund/European Social Fund.

Electrogram fractionation during atrial fibrillation (AF) and sinus rhythm have been studied as marker of atrial remodeling and potential target for ablation.

The aim of our study was to analyze the response to closely coupled atrial extrastimuli and try to identify areas of hidden slow conduction (HSC) that can promote reentry and AF maintenance in paroxysmal and persistent AF.

Twenty consecutive patients with paroxysmal AF and persistent AF (10:10) underwent first PVI procedure. During sinus rhythm triple short coupled extrastimuli was delivered. Locations showing double or highly fragmented electrograms in response to triple extrastimuli were defined as positive electrogram (HSC-EGM) (Figure 1). Increase in duration (delta) of the bipolar EGM was recorded. Two consecutive high-density maps were acquired using a multipolar catheter during AF, sinus and paced rhythms. Spatial correlation of HSC-EGM and complex atrial fractionation (CFAEs) during AF were evaluated.

Patients with persistent AF showed a higher number and percentage of HSC-EGM than paroxysmal AF (13,9% vs 3,3%, p<0.001) (Figure 2). Delta of EGM duration was 53 ± 22 ms compared to 16 ± 14 ms in sites with a negative response (p<0.001). The number of HSC-EGM distinguished with extrastimuli was lower than that of CFAEs during AF (19 vs 56 per map, p<0.01). The reproducibility of the extension and distribution of HSC-EGM in the repeated maps was superior to that of the CFAEs. The distribution of the HSC-EGM was comparable with those found in the initial map (p=0,32), however, there were significant differences in the distribution of CFAEs between the first map and the remap (p=0.003).

HSC-EGM in response to triple extrastimuli are more frequent in persistent AF. This type of evoked response could reveal the presence of slow conduction areas and could be considered a potential target for ablation of persistent atrial fibrillation. More studies are needed to confirm this hypothesis.