Rotors
The idea of rotors as a mechanism for AF has been proposed since 1990 (39,40) and currently is defined as a cyclic activation producing spiral waves which radiate outward into the surrounding tissue around a core of functional block, as opposed to an area of scar tissue, which allow rotors to “move” up to 2-3 cm2 around the atrium (41). Interestingly, a significant proportion of rotors have been described in the right atrium (an area not normally targeted during AF ablation) (42), making focal impulse and rotor modulation (FIRM) an appealing adjunctive strategy(43). Although the CONFIRM (Conventional Ablation for Atrial Fibrillation With or Without Focal Impulse and Rotor Modulation) study reported a high degree of freedom from AF with FIRM (42), other studies have demonstrated that, despite the association with a more organized fibrillatory activation within the LA, it does not correlate with an increase in freedom from AF, even after redo procedures (43-46). Furthermore, a head-to-head meta-analysis of six studies including 716 patients (88.5% non-PAF) concluded that FIRM did not add any benefit in improving all-atrial arrhythmia recurrence (47). (Figure 5)