Abstract
Background: Presence of left atrial low voltage substrate in bipolar voltage mapping is associated with increased arrhythmia recurrences following pulmonary vein isolation for atrial fibrillation (AF). Besides local myocardial fibrosis, bipolar voltage amplitudes may be influenced by inter-electrode spacing and bipole-to-wavefront-angle. It is unclear to what extent these impact low voltage areas (LVA) in the clinical setting. Alternatively, unipolar electrogram voltage is not affected by these factors but requires advanced filtering.Objectives: To assess the relationship between bipolar and unipolar voltage mapping in sinus rhythm (SR) and AF and identify if the electrogram recording mode affects the quantification and localization of LVA.Methods: Patients (n = 28, 66±7 years, 46% male, 82% persistent AF, 32% redo-procedures) underwent high-density (>1,200 sites, 20 ± 10 sites/cm2, using a 20-pole 2-6-2 mm-spaced Lasso) voltage mapping in SR and AF. Bipolar LVA were defined using four different thresholds described in literature: <0.5 and <1 mV in SR, <0.35 and <0.5 mV in AF. The optimal unipolar voltage threshold resulting in the highest agreement in both unipolar and bipolar mapping modes was determined. The impact of the inter-electrode distance (2 vs. 6 mm) on the correlation was assessed. Regional analysis was performed using an 11-segment left atrial model.Results: Patients had relevant bipolar LVA (23 ± 23 cm2 at <0.5 mV in SR and 42 ± 26 cm2 at <0.5 mV in AF). 90 ± 5% (in SR) and 85 ± 5% (AF) of mapped sites were concordantly classified as high or low voltage in both mapping modes. Discordant mapping sites located to the border zone of LVA. Bipolar voltage mapping using 2 vs. 6 mm inter-electrode distances increased the portion of matched mapping points by 4%. The unipolar thresholds (y) which resulted in a high spatial concordance can be calculated from the bipolar threshold (x) using following linear equations: y = 1.06x + 0.26mV (r = 0.994) for SR and y = 1.22x + 0.12mV (r = 0.998) for AF.Conclusion: Bipolar and unipolar voltage maps are highly correlated, in SR and AF. While bipole orientation and inter-electrode spacing are theoretical confounders, their impact is unlikely to be of clinical importance for localization of LVA, when mapping is performed at high density with a 20-polar Lasso catheter.
Highlights
Atrial fibrillation (AF) is the most common supraventricular cardiac arrhythmia characterized by an irregular heart rhythm and associated with an increased risk of heart failure, stroke, and mortality (Wang et al, 2003; Miyasaka et al, 2005; Go et al, 2014).Pulmonary veins have been identified as major arrhythmogenic trigger sites for AF
We evaluate the correlation between the two mapping methods and identify the corresponding unipolar thresholds that yield the highest concordance to the bipolar low voltage areas (LVA)
The current study on bipolar vs. unipolar voltage mapping reveals three main findings: 1. There is a high correlation in the spatial distribution of uniand bipolar low voltage areas in sinus rhythm and atrial fibrillation
Summary
Atrial fibrillation (AF) is the most common supraventricular cardiac arrhythmia characterized by an irregular heart rhythm and associated with an increased risk of heart failure, stroke, and mortality (Wang et al, 2003; Miyasaka et al, 2005; Go et al, 2014).Pulmonary veins have been identified as major arrhythmogenic trigger sites for AF. Procedural identification of arrhythmogenic AF sources with rapid, continuous, or repeated rotational activity has revealed their localization within fibrotic regions displaying low bipolar voltage
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