Discussion
In this study, we aimed to determine if pacing site and the rhythm during AF ablation affect procedural characteristics, and most importantly catheter stability. We have recently demonstrated that improved spatial catheter stability is associated with lower rates of arrhythmia recurrence after AF ablation8. Therefore, it is important to understand the interaction of the atrial rhythm during AF ablation and catheter spatial stability.
Our data suggests that catheter ablation during atrial fibrillation with ventricular pacing, compared to sinus rhythm with atrial pacing, does not result in significant differences in high-resolution catheter spatial stability and lesion quality. Despite the difference in the underlying atrial rhythm, measures of catheter stability were similar between the two groups. In fact, ventricular-paced patients had significantly greater average contact forces (and subsequently greater FTIs), suggesting maintaining adequate catheter-tissue contact may be easier during atrial fibrillation, when there is less myocardial motion. There were also no differences in impedance decline between atrial paced and ventricular paced patients.
Ventricular-paced patients had longer procedure times and trended towards a greater number of electrical cardioversions. This can be explained by the fact that some patients in this group had unsuccessful cardioversion attempts at the beginning of the procedure, which led to the decision to perform ablation in AF with ventricular pacing instead. All ventricular-paced patients in our study were successfully cardioverted to sinus rhythm by procedure end.
Catheter ablation of persistent atrial fibrillation remains a therapeutic challenge, with high recurrence rates and frequent need for repeat ablations. The arrhythmogenic substrate in persistent atrial fibrillation is complex and incompletely elucidated, and although the pulmonary veins and posterior wall are frequently implicated, there is no consensus regarding optimal ablation targets or strategy15–19. Whereas the majority of ectopic foci in paroxysmal AF reside within the pulmonary vein-left atrial interface20,21, the mechanisms behind persistent AF are more complex and often the result of long-standing atrial remodeling22,23. Underlying atrial myopathy and fibrosis, particularly within the posterior wall of the left atrium, can serve as additional triggers and propagators of persistent AF. Voltage mapping can be performed to identify areas of scar and fibrosis, although previous data has shown that voltage amplitudes are affected by the underlying atrial rhythm24–26. A recent study by Qureshi et al. found that mapping during atrial fibrillation, compared to sinus rhythm, may actually be more sensitive and specific in identifying low voltage regions that correlate with atrial fibrosis on cardiac MRI27. More accurate intra-procedural voltage mapping would provide invaluable information regarding identifying arrhythmogenic substrate and refining ablation strategy.
Overall one year arrhythmia-free survival was 73%, which is in line with previous data for persistent AF ablation4,6,7 and there was no significant difference in recurrence between the atrial-paced and ventricular-paced patients. The ventricular-paced patients had significantly greater LA diameters, time since AF diagnosis, as well as trend toward greater LA volume indices and lower LV ejection fraction. These measures have been shown to be associated with increased arrhythmia recurrence28–31 thus sample size may have confounded recurrence outcomes.