New Insights Into Understanding Rotor Versus Focal Activation in Patients With Persistent Atrial Fibrillation

Abstract

Objectives: This study was to test the hypotheses that: 1) when using phase analysis, repetitive Wannabe re-entry produces a phase singularity point (i.e., a rotor); and 2) the location of the stable rotor is close to the focal source.

Background: Recent contact mapping studies in patients with persistent atrial fibrillation (AF) demonstrated that phase analysis produced a different mechanistic result than classical activation sequence analysis. Our studies in patients with persistent AF showed that focal sources sometimes produced repetitive Wannabe re-entry, that is, incomplete re-entry.

Methods: During open heart surgery, we recorded activation from both atria simultaneously using 510 to 512 electrodes in 12 patients with persistent AF. We performed activation sequence mapping and phase analyses on 4 s of mapped data. For each detected stable rotor (>2 full rotations [720°] recurring at the same site), the corresponding activation patterns were examined from the activation sequence maps.

Results: During AF, phase singularity points (rotors) were identified in both atria in all patients. However, stable phase singularity points were only present in 6 of 12 patients. The range of stable phase singularity points per patient was 0 to 6 (total 14). Stable phase singularity points were produced due to repetitive Wannabe re-entry generated from a focal source or by passive activation. A conduction block sometimes created a stable phase singularity point (n = 2). The average distance between a focal source and a stable rotor was 0.9 ± 0.3 cm.

Conclusions: Repetitive Wannabe re-entry generated stable rotors adjacent to a focal source. No true re-entry occurred.

Keywords: atrial fibrillation; focal sources; mapping; reentry; rotors.

Figure 1:

Panel A: Conceptually simplified examples of two consecutive beats showing collision with a line of block creating repetitive wannabe reentry. Left panel, a repetitive wannabe reentry generated by a wavefront emanating from a focal source. Right panel, a repetitive wannabe reentry generated by a passive wavefront. Panel B: Flow chart of the phase analysis and the signal processing procedures that were applied to the original bipolar AEGs. Panel C: Each bipolar site was assigned a 2×2 grid of surrounding bipolar neighboring sites. Each bipolar site and four surrounding bipolar sites were used for the determination of focal activation and a rotor activation. AEGs, atrial electrograms

Figure 2.

A representative example (patient #12) showing repetitive wannabe reentry generated from a focal source producing a stable phase singularity point. Panel A: Two consecutive beats of left atrial phase map during AF showing the location of recording sites (a through e) and a stable phase singularity point (white dot). Phase value color bar (0 [-π] to 1 [π]) is shown on the right. Panel B: Two consecutive beats of left atrial activation sequence map during AF. The 10 millisecond isochronal color bar is shown on the right. The black arrows indicate activation wavefronts. Panel C Top: Bipolar AEGs with their phase from selected sites (a – e). The red arrow indicates a wannabe reentry activation for the activation sequence map shown in panel B. The block dot arrow indicates a rotor activation for the phase map shown in panel A. Bottom: Bipolar AEGs at the stable phase singularity point. See text for discussion. LAA, left atrial appendage; LIPV, left inferior pulmonary vein; LSPV, left superior pulmonary vein

Figure 3:

A representative example (patient #3) showing repetitive wannabe reentry generated from a passive wavefront entering from the edge of recording array producing a stable phase singularity point. Panel A: Two consecutive beats of a left atrial phase map during AF showing the location of recording sites (a through d), and a stable phase singularity point (white dot). Phase value color bar (0 [-π] to 1 [π]) is shown on the right. Panel B: Two consecutive beats from a left atrial activation sequence map during AF. The 10 millisecond isochronal color bar is shown on the right. The black arrows indicate activation wavefronts. Panel C Top: Bipolar AEGs with their phase from selected sites (a – d). The red arrow indicates a wannabe reentry activation for the activation sequence map shown in panel B. The black dot arrow indicates a rotor activation for the phase map shown in panel A. Bottom: Bipolar AEGs at the stable phase singularity point. See text for discussion. LAA, left atrial appendage; LIPV, left inferior pulmonary vein; LSPV, left superior pulmonary vein

Figure 4:

A representative example (patient #10) showing conduction block generated from a focal source producing two stable phase singularity points. Panel A: Two consecutive beats of left atrial phase map during AF showing the location of recording sites (a through k) and two stable phase singularity points (white dots). Phase value color bar (0 [−π] to 1 [π]) is shown on the right. Panel B: Two consecutive beats from a left atrial activation sequence map during AF. The 10 millisecond isochronal color bar is shown on the right. The black arrows indicate activation wavefronts. Panel C: Bipolar AEGs with their phase from selected sites (a - k). The red arrow indicates wavefront activations for the activation sequence map shown in panel B. The black dot arrow indicates a rotor activation for the phase map shown in panel A. See text for discussion. LAA, left atrial appendage; LIPV, left inferior pulmonary vein; LSPV, left superior pulmonary vein

Figure 5:

Selected bipolar AEGs along with each unipolar component (QS morphology and RS morphology) of the bipolar AEG from the focal source (site d). The power spectrum with dominant frequency is shown on the right. See text for discussion.

Central Illustration