Electrographic flow mapping for atrial fibrillation: theoretical basis and preliminary observations

Abstract

Ablation strategies remain poorly defined for persistent atrial fibrillation (AF) patients with recurrence despite intact pulmonary vein isolation (PVI). As the ability to perform durable PVI improves, the need for advanced mapping to identify extra-PV sources of AF becomes increasingly evident. Multiple mapping technologies attempt to localize these self-sustained triggers and/or drivers responsible for initiating and/or maintaining AF; however, current approaches suffer from technical limitations. Electrographic flow (EGF) mapping is a novel mapping method based on well-established principles of optical flow and fluid dynamics. It enables the full spatiotemporal reconstruction of organized wavefront propagation within the otherwise chaotic and disorganized electrical conduction of AF. Given the novelty of EGF mapping and relative unfamiliarity of most clinical electrophysiologists with the mathematical principles powering the EGF algorithm, this paper provides an in-depth explanation of the technical/mathematical foundations of EGF mapping and demonstrates clinical applications of EGF mapping data and analyses. Graphical abstract Starting with a 64-electrode basket catheter, unipolar EGMs are recorded and processed using an algorithm to visualize the electrographic flow and highlight the location of high prevalence AF “source” activity. The AF sources are agnostic to the specific mechanisms of source signal generation.

Rotor mechanism and its mapping in atrial fibrillation

“…An algorithm that combined Green’s minimal bending energy algorithm and Horn–Schunck Flow algorithm was used to analysed the time-domain information from the unipolar electrograms collected by a basket-like catheter and converted it into the space domain of flow vectors for the identification of singularities where the flow vector angles around a point covered 360°. 43 One strength of this method is the potential to distinguish active and passive rotors. Theoretically, it can make up for insufficient local resolution of the basket-like catheter.…”

Analysis of the Time-Dependent Behaviors of Atrial Fibrillation with Electrographic Flow Mapping

“…10,11,13,14,25,26 The present study employed a novel mapping algorithm using atrial electrograms recorded from a low-density 64-pole basket, and Green's formula-based spline interpolation with Horn-Schunck's iterative flow estimation to generate reproducible patterns of electrographic flow. 18 Although the present system is subject to the same limitations experienced by other systems that have employed low-density basket electrode recordings, our goal is to identify broad wavefronts of activation, not to dissect the intricacies of source mechanisms at their sites of origin. The anticipated wavelength of these broad atrial electrical wavefronts is estimated to be greater than 10 cm, which is significantly greater than the interelectrode spacing of a basket electrode catheter and therefore within the resolution of the low-density electrode array.…”

“…The details of electrogram acquisition and processing have been described in detail. 18 In brief, signals were filtered at 0.05 – 500 Hz and recorded at 1kHz sampling frequency for export from the electrophysiology recording system. The EGF mapping system pre-processes unipolar EGMs to remove the time segment containing the QRS complex from the recording and then normalizes the signals to unitary amplitudes prior to processing.…”

2024 European Heart Rhythm Association/Heart Rhythm Society/Asia Pacific Heart Rhythm Society/Latin American Heart Rhythm Society expert consensus statement on catheter and surgical ablation of atrial fibrillation

“…Electrographic flow mapping (Ablamap, Ablacon) utilizes a large basket catheter to record unipolar electrograms, which are then interpolated and processed into a beat-by-beat electrical intensity map. 563 As the electrical intensity changes beat-by-beat in AF, the Horn–Schunk iterative algorithm calculates the flow pattern seen during AF over time. Regions with divergent flow patterns can be labelled as ‘sources’, which can then be targeted for ablation.…”