Identification of Rotors during Human Atrial Fibrillation Using Contact Mapping and Phase Singularity Detection: Technical Considerations.

OBJECTIVE: To explore technical challenges of phase singularity (PS) mapping during atrial fibrillation (AF) using direct contact electrograms.
METHODS: AF mapping was performed in high-density epicardial recordings of human paroxysmal (PAF) or persistent (PersAF) (N = 20 pts) AF with an array of 16 × 16 electrodes placed on atrial epicardium. PS points were detected using subsets of electrodes forming rings of varying sizes.
RESULTS: PS detection using a 2 × 2 electrode ring identified 0.88 ± 1.00 PS/s in PAF group and 3.91 ± 2.51 per s in PersAF group (p < 0.001) in 2.4 × 2.4 cm mapping area. All detected PS had a short lifespan with the longest being 1100 ms (6.8 rotations). Exploration of the PS detection in a numerical model demonstrated that at least eight electrodes are required to avoid frequent false positive PS detection due to chance. Application of a detection grid consisting a double ring of electrodes (2 × 2 and 4 × 4 rings) decreased the number of false positive detections. The double ring was more resilient to electrode swapping (with just three instances of false positives versus 4380 false positives using 2 × 2 ring).
CONCLUSIONS: The number of detected rotors critically depends upon the parameters of the detection algorithm, especially the number of electrodes used to detect PS. Based on our results, we recommend double ring comprised of 2 × 2 and 4 × 4 grid of electrodes for robust rotor detection. SIGNIFICANCE: Great methodological care has to be taken before equating detected PS with rotating waves and using PS detection algorithms to guide catheter ablation of AF.