Simultaneous epicardial–endocardial mapping of the sinus node in humans with structural heart disease: impact of overdrive suppression on sinoatrial exits

Abstract

Background: The 3-dimensional (3D) nature of sinoatrial node (SAN) function has not been characterized in the intact human heart. Objective: The purpose of this study was to characterize the 3D nature of SAN function in patients with structural heart disease (SHD) using simultaneous endocardial-epicardial (endo-epi) phase mapping. Methods: Simultaneous intraoperative endo-epi SAN mapping was performed during sinus rhythm at baseline (SR(baseline)) and postoverdrive suppression at 600 ms (SR(post-pace600)) and 400 ms (SR(post-pace400)) using 2 Abbott Advisor HD Grid Mapping Catheters. Unipolar and bipolar electrograms (EGMs) were exported for phase analysis to determine (1) activation exits; (2) wavefront propagation sequence; (3) endo-epi dissociation; and (4) fractionation. Comparison of these variables was made among the 3 rhythms from an endo-epi perspective. Results: Sixteen patients with SHD were included. SR(baseline) activations were unicentric and predominantly exited cranially (87.5%) with endo-epi synchrony. However, with overdrive suppression, a tendency for caudal exit shift and endo-epi asynchrony was observed: SR(post-pace600) vs SR(baseline): cranial endo 75% vs 87.5% (P = .046); cranial epi 68.8% vs 87.5% (P = 0.002); caudal endo 12.5% vs 6.2% (P = 0.215); caudal epi 25% vs 6.2% (P = .0003); and SR(post-pace400) vs SR(baseline): cranial endo 81.3% vs 87.5% (P = 0.335); cranial epi 68.7% vs 87.5% (P = 0.0034; caudal endo 12.5% vs 6.2% (P = .148); caudal epi 31.2% vs 6.2% (P = 0.0017), consistent with multicentricity. EGM fractionation was more prevalent with overdrive suppression. Conclusion: During mapping of the intact human heart, SAN demonstrated redundancy of sinoatrial exits with postoverdrive shift in sites of earliest activation and epi-endo dissociation of sinoatrial exits.