Epiphenomenal Re-Entry and Spurious Focal Activation Detection by Atrial Fibrillation Mapping Algorithms

Abstract

Objectives: The purpose of this study was to validate the ability of mapping algorithms to detect rotational activations (RoA) and focal activations (FoA) during fibrillatory conduction (FC) and atrial fibrillation (AF) and understand their mechanistic relevance.

Background: Mapping algorithms have been proposed to detect RoA and FoA to guide AF ablation.

Methods: Rapid left atrial pacing created FC-fibrillatory electrograms-with and without AF induction in dogs (n = 17). Activation maps were constructed using Topera (Abbott, St. Paul, Minnesota) or CARTOFINDER (Biosense Webster, Irvine, California) algorithms. Mapping strategies included: panoramic noncontact mapping with a basket catheter (CARTOFINDER n = 6, Topera n = 5); and sequential contact mapping using 8-spline OctaRay catheter (Biosense Webster) (n = 6). Offline frequency and spectral analysis were also performed. Algorithm-detected RoA was manually verified.

Results: The right atrium (RA) consistently exhibited fibrillatory signals during FC. FC with and without AF had similar left-to-right frequency gradients. Basket maps were either uninterpretable (847 of 990 Topera, 132 of 148 Cartofinder) or had unverifiable RoA. OctaRay contact mapping showed 4% RoA (n = 30 of 679) and 63% FoA (n = 429 of 679). Verified RoA clustered at consistent sites, was more common in the RA than left atrium (odds ratio: 3.5), and colocalized with sites of frequency breakdown in the crista terminalis and RA appendage. During pacing, spurious FoA sites were identified around the atria, but not at the actual pacing sites. RoA and FoA site distribution was similar during pacing with and without induction, and during induced AF.

Conclusions: Mapping algorithms were unable to detect pacing sites as true drivers of FC, and detected epiphenomenal RoA and FoA sites unrelated to AF induction or maintenance. Algorithm-detected RoA and FoA did not identify true AF drivers.

Keywords: 3D; CARTOFINDER; atrial fibrillation; focal activation; frequency; mapping; repetitive patterns; rotational activation; rotors; spectral analysis.

FIGURE 1. Experimental Setup

(A to C) Fluoroscopy of catheter arrangement. Basket catheter in the right atrium (RA) (A) and in the left atrium (LA) (B). (C) OctaRay catheter in the LA. (D to F) Examples of fibrillatory electrograms in the RA during rapid LA pacing from the right superior pulmonary vein (RSPV) (D), coronary sinus (CS) (E), or both (F).

FIGURE 2. DF and its Regularity Index During Induced AF and Pacing With FC

(A) Fibrillatory electrograms during pacing from the RSPV at 140 ms (7.2 Hz) without AF induction. The phenomenon of FC is most apparent in the RA tracing. Note the decrease in RI of the DF in the frequency spectrum due to the less than 1-to-1 conduction underlying the FC. (B) Induced AF after pacing from the RSPV at 120 ms (8.4 Hz). (C) Schematic of RI frequency calculation. (D) DF regularity during pacing with and without AF induction: note the similar spatial distribution. (E) DF during pacing with FC and induced AF. Note the L-to-R frequency gradient between L and R atrial sites during AF. (F) DF regularity during AF. AF = atrial fibrillation; DF = dominant frequency; FC = fibrillatory conduction; L = left; R = right; RA = right atrium; RI = regularity index; RSPV = right superior pulmonary vein.

FIGURE 3. Dominant Frequency Maps During Pacing at 140 ms (7.1 Hz) From the RSPV With FC

Septal (A) and right lateral (B) view of the RA. AP (C) and PA (D) view of the LA. Note the frequency variation in the lateral wall of the RA (B) despite the 1-to-1 conduction in the LA (more uniform frequencies in C and D). (E) Time and frequency domains of the 5 points shown in A to D. Note the frequency breakdown and the less than 1-to-1 conduction in point 3 (corresponding to the crista terminalis in the RA). (F) DF regularity index maps showing the power ratio of the pacing frequency (7.1 Hz) in both atria. Note the increased frequency variability (less regularity) (blue) in the lateral wall of the RA due to the less than 1-to-1 conduction despite high regularity in the LA (red). Also note, spectral contamination with ventricular signals leads to decreased DF regularity around the mitral valve area. AP = anteroposterior; CS os = coronary sinus ostium; LAA = left atrial appendage; LSPV = left superior pulmonary vein; MV = mitral valve; PA = posteroanterior; RAA = right atrial appendage; SVC = superior vena cava; other abbreviations as in Figure 2.

FIGURE 4. FoA Detection by the Cartofinder System

Lateral (A) and septal (B) view of the RA and PA view of the LA during pacing from the RSPV (A) and CS (B) showing FoA at distant sites. Note that the system fails to identify the pacing sites as an FoA. CPV = common pulmonary vein; FoA = focal activations; LIPV = left inferior pulmonary vein; other abbreviations as in Figures 1 to 3.

FIGURE 5. Fibrillatory Conduction During Dual-Site, Dual-Cycle Length Pacing From the RSPV at 200 ms (5 Hz) and Distal CS at 180 ms (5.6 Hz)

Frequency maps showing the distribution of the slower (5 Hz, blue) and faster (5.6 Hz, red) frequencies in an anterior (A) and posterior (B) view of the LA and a lateral (C) and septal (D) view of the RA. (E and F) RI maps of the 2 pacing frequencies. The maximum RI of 5 Hz is located near the RSPV and 5.6 Hz near the distal CS, demonstrating a correct identification of the 2 pacing sites. Also note the power gradient along the LA posterior wall moving away from the pacing site. (G and H) Cartofinder maps showing spurious annotations of FoA in the LA (green), with failure to identify either pacing site as a FoA. (I) Time and frequency domains of the 4 points identified in E and F. Abbreviations as in Figures 1, 2, and 4.

CENTRAL ILLUSTRATION. Epiphenomenal Re-Entry and Spurious Focal Activation During Rapid Pacing Without AF Induction

In an in vivo canine model, rapid left atrial (LA) pacing led to fibrillatory conduction with fibrillatory electrograms in the right atrium (RA) without atrial fibrillation (AF) induction (top). Cartofinder algorithm identified RoA most commonly in the RA, and spurious FoA sites away from the pacing site. The epiphenomenal nature of RoA in the absence of AF and the spurious FoA site identification question the value of mapping algorithms to guide ablation. CS = coronary sinus; FoA = focal activation; LIPV = left inferior pulmonary vein; RoA = rotational activations; RSPV = right superior pulmonary vein.