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.