Dynamic Atrial Substrate DuringHigh-Density Mapping of Paroxysmal and Persistent AF: Implications for Substrate Ablation.

Abstract

This study sought to determine the impact of rate and direction on left atrial (LA) substrate. The extent to which substrate mapped in sinus rhythm varies according to cycle length and direction of wave front propagation is unknown. A total of 73 consecutive patients with atrial fibrillation (AF) underwent electroanatomic LA mapping before pulmonary vein isolation using multipolar catheter during distal coronary sinus (CS) pacing at 600ms and 300ms. Additional maps were created during left superior pulmonary vein pacing at 300ms. Bipolar voltage, conduction velocity (CV), and complex signals were determined. Mean age was 61 ± 9 years, 67% were men, and 53% had persistent AF. Global mean voltage was lower with CS pacing at 300ms compared with 600ms (1.56 ± 0.47 mV vs. 1.74 ± 0.48mV; p<0.001). This was seen in all LA segments. Global CV was reduced (30.4 ± 13.0cm/s vs. 38.6 ± 14.0cm/s; p<0.001) with greater complex signals at 300ms (8.9% vs. 5.3%; p<0.005). Compared with CS pacing, left superior pulmonary vein pacing demonstrated highly regional changes with decreased voltage (1.04 ± 0.43mV vs. 1.47 ± 0.53mV; p= 0.01) and CV (24.4 ± 13.0cm/s vs. 39.9 ± 16.6cm/s; p= 0.008), and greater complex signals posteriorly. Longer AF duration in paroxysmal AF (p= 0.02) and shorter duration in persistent AF (p= 0.015) and left ventricular ejection fraction (p= 0.016) were independent predictors of voltage change. In patients with AF, variation in cycle length and direction of wave front activation produce both generalized and regional changes in voltage, CV, and complex fractionation, resulting in significant changes in substrate maps. This study highlights the potential limitations of static low-voltage maps to identify the AF ablation target zone.