Factors affecting basket catheter detection of real and phantom rotors in the atria: A computational study

Abstract

Anatomically based procedures to ablate atrial fibrillation (AF) are often successful in terminating paroxysmal AF. However, the ability to terminate persistent AF remains disappointing. New mechanistic approaches use multiple-electrode basket catheter mapping to localize and target AF drivers in the form of rotors but significant concerns remain about their accuracy. We aimed to evaluate how electrode-endocardium distance, far-field sources and inter-electrode distance affect the accuracy of localizing rotors. Sustained rotor activation of the atria was simulated numerically and mapped using a virtual basket catheter with varying electrode densities placed at different positions within the atrial cavity. Unipolar electrograms were calculated on the entire endocardial surface and at each of the electrodes. Rotors were tracked on the interpolated basket phase maps and compared with the respective atrial voltage and endocardial phase maps, which served as references. Rotor detection by the basket maps varied between 35–94% of the simulation time, depending on the basket’s position and the electrode-to-endocardial wall distance. However, two different types of phantom rotors appeared also on the basket maps. The first type was due to the far-field sources and the second type was due to interpolation between the electrodes; increasing electrode density decreased the incidence of the second but not the first type of phantom rotors. In the simulations study, basket catheter-based phase mapping detected rotors even when the basket was not in full contact with the endocardial wall, but always generated a number of phantom rotors in the presence of only a single real rotor, which would be the desired ablation target. Phantom rotors may mislead and contribute to failure in AF ablation procedures.

Author summary

In computer simulations we determined the accuracy of using multiple-electrode basket catheters to detect atrial fibrillation sources (rotors) during an ablation procedure. We used a realistic 3D atrial model and a virtual multiple-electrode basket catheter placed in three different positions inside the right atrium. The ability to detect a true rotor depended on three major factors: 1) the position of the basket inside the atrium, 2) the distance between the electrodes and the atrial wall, and 3) the inter-electrode distance. When the electrodes were not in full contact with the atrial wall far-field sources predominated on the recorded signal. As a consequence, phantom rotors were generated on the maps. Interpolation of the signals increased the false rotor incidence, whereas increasing the electrode density decreased it. We conclude that the appearance of false rotors might contribute to AF ablation procedure failure because the physician may erroneously target atrial tissue locations where no true rotor exists.