Electrogram fractionation in murine HL-1 atrial monolayer model.

Background: Complex fractionated atrial electrograms have been suggested as important targets for catheter ablation of atrial fibrillation. The etiology and the mechanism of these signals have not been completely elucidated because of limitations of interpretation of these signals in relation to simultaneously acquired signals in the neighboring atrial tissue.

Objective: This study sought to study the origin of electrogram fractionation under the conditions of rotor formation and wave fragmentation, using atrial monolayer preparations.

Methods: We performed optical mapping of 45 atrial monolayer preparations using a complementary metal oxide semiconductor (CMOS) Brainvision Ultima camera system (SciMedia-Brainvision, Tokyo, Japan).

Results: We observed stable rotors in 32 of the 45 recordings. The derived bipolar electrograms did not show complex fractionation at the core of the rotor in any of the 32 recordings. We were also able to show that 2 bipolar electrodes placed adjacent to the core of a stable rotor in a zone where there is no wave break will record electrical activity for the majority of the rotor's cycle length. In 13 of the 45 recordings, wave break or wave collision events were present. Of these, 8 of 13 recordings showed complex fractionation. In 19 of the 27, simulation of meandering rotors also showed complex fractionation.

Conclusion: Complex fractionated electrograms can be recorded at sites of migrating rotors and wave break. No fractionation occurs at the core of a stable rotor. Electrograms that span the rotor cycle length and alternate between 2 bipoles that straddle the core can identify site of a stable rotor.