Simultaneous endo-epicardial mapping of the human sinus node in patients undergoing cardiac surgery

Abstract

Abstract Introduction Conduction disorders in the right atrium (RA) are predominantly observed in the superior part. Presence of the sinoatrial node (SAN) in this region could be contributing to increased heterogeneity in activation patterns. However, mapping studies focusing on SAN activation are scarce. Purpose The aim of the present study was to analyze activation patterns of the human SAN during sinus rhythm. Methods A dataset containing simultaneous endo-epicardial mapping data (256 electrodes, inter-electrode spacing: 2mm) of RA was screened for focal activation patterns (FAPs) potentially arising from SAN activation (SN-FAP). Conduction time, endo-epicardial delay and electrogram morphology (R/S-ratio) were described in the surrounding 1cm of SN-FAPs. Areas of conduction block (CB) were defined as conduction delays of ≥12ms and endo-epicardial asynchrony (EEA) as activation time differences of exact opposite electrodes of ≥15ms. Results In 20 patients (75% male, 66±7 years) a total of 28 SN-FAPs with unique activation patterns were observed only in superior RA (n=22) and mid RA (n=6). Conduction velocity of SN-FAPs was 1.3m/s [0.8–2.5] and percentage of EEA was 5% [2–18]. Conduction velocity was lower when lines of CB were present within 6mm of the SN-FAPs (p=0.040). Significantly larger R-peaks were observed in mid RA compared to superior RA. (mid R/S-ratio:0.15 [0.067–0.34] vs. superior R/S-ratio:0.045 [0.026–0.062], p=0.004). Conclusions Conduction velocities around the SAN area are comparable to the remainder of the atria. SN-FAPs occurred in both superior and mid RA, suggesting presence of multiple exit sites of the SAN. Furthermore, inter-individual differences in rS-morphology indicate that SAN activation may originate from multiple layers within the atrial wall. Funding Acknowledgement Type of funding source: None