Abstract
BackgroundBipolar electrogram voltage during sinus rhythm (VSR) has been used as a surrogate for atrial fibrosis in guiding catheter ablation of persistent atrial fibrillation (AF), but the fixed rate and wavefront characteristics present during sinus rhythm may not accurately reflect underlying functional vulnerabilities responsible for AF maintenance.ObjectiveThe purpose of this study was determine whether, given adequate temporal sampling, the spatial distribution of mean AF voltage (VmAF) better correlates with delayed-enhancement magnetic resonance imaging (MRI-DE)–detected atrial fibrosis than VSR.MethodsAF was mapped (8 seconds) during index ablation for persistent AF (20 patients) using a 20-pole catheter (660 ± 28 points/map). After cardioversion, VSR was mapped (557 ± 326 points/map). Electroanatomic and MRI-DE maps were co-registered in 14 patients.ResultsThe time course of VmAF was assessed from 1–40 AF cycles (∼8 seconds) at 1113 locations. VmAF stabilized with sampling >4 seconds (mean voltage error 0.05 mV). Paired point analysis of VmAF from segments acquired 30 seconds apart (3667 sites; 15 patients) showed strong correlation (r = 0.95; P <.001). Delayed enhancement (DE) was assessed across the posterior left atrial (LA) wall, occupying 33% ± 13%. VmAF distributions were (median [IQR]) 0.21 [0.14–0.35] mV in DE vs 0.52 [0.34–0.77] mV in non-DE regions. VSR distributions were 1.34 [0.65–2.48] mV in DE vs 2.37 [1.27–3.97] mV in non-DE. VmAF threshold of 0.35 mV yielded sensitivity of 75% and specificity of 79% in detecting MRI-DE compared with 63% and 67%, respectively, for VSR (1.8-mV threshold).ConclusionThe correlation between low-voltage and posterior LA MRI-DE is significantly improved when acquired during AF vs sinus rhythm. With adequate sampling, mean AF voltage is a reproducible marker reflecting the functional response to the underlying persistent AF substrate.
Highlights
Atrial fibrosis is known to play an important role in the maintenance of atrial fibrillation (AF)
VmAF threshold of 0.35 mV yielded sensitivity of 75% and specificity of 79% in detecting MRI-Delayed enhancement (DE) compared with 63% and 67%, respectively, for voltage during sinus rhythm (VSR) (1.8-mV threshold)
The correlation between low-voltage and posterior left atrial (LA) MRI-DE is significantly improved when acquired during AF vs sinus rhythm
Summary
Atrial fibrosis is known to play an important role in the maintenance of atrial fibrillation (AF). By interfering with electrical continuity, fibrotic tissue is vulnerable to slow conduction, refractory dispersion, and functional reentry, perpetuating AF.[1] The optimal method of identifying de novo atrial fibrosis in persistent AF remains unclear. Low-amplitude bipolar electrograms (EGMs) have been used as an electrical surrogate for fibrosis while mapping during sinus rhythm (SR).[5,6] EGM amplitudes can be influenced by many factors. Bipolar electrogram voltage during sinus rhythm (VSR) has been used as a surrogate for atrial fibrosis in guiding catheter ablation of persistent atrial fibrillation (AF), but the fixed rate and wavefront characteristics present during sinus rhythm may not accurately reflect underlying functional vulnerabilities responsible for AF maintenance
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