Discussion.
The present study confirms the high success rate of pulmonary vein
isolation using ablation index: Our long-term results, with freedom from
atrial fibrillation in 84% of patients, are similar to those achieved
by other groups using ablation index.18-21
Previous studies have shown a higher rate of first pass isolation using
ablation index compared to conventional ablation settings and force time
integral (FTI) and the need for ablation of the carina in case of lack
of first pass isolation.18 20 22 In all these studies,
the ablation was conducted with a circular mapping catheter positioned
at the pulmonary vein to confirm isolation during the ablation through
as double trans-septal approach. In contrast, in the present study we
demonstrate that a strategy of ablation solely based on the use of the
ablation catheter through a single trans-septal punctureconsisting of WACA plus empiric carina ablation guided by ablation
index , can reliably achieve high percentages of first pass isolation.
Moreover, the confirmation of pulmonary vein isolation can be
effectively performed with the use of the ablation catheter only by the
identification of residual electrograms distal to the WACA and by pacing
maneuvers demonstrating exit block. A strategy solely based on the use
of the ablation catheter via single trans-septal crossing, has several
potential advantages. Every trans-septal puncture potentially involves
important risk of complications in particular pericardial effusion and
tamponade, inadvertent puncture of the aorta or air
embolism.23-25 A single trans-septal puncture would
intuitively results in a lower incidence of complications. Also, use of
only an ablation catheter would results in reduction in procedural
costs. Finally, having only one (as opposed to two catheters) in the
left atrium, simplifies catheter manipulation during the ablation
procedure, particularly in small atria.
The role of carina ablation to achieve pulmonary vein isolation has been
previously reported26-29 and is here confirmed. In our
study first pass isolation was significantly higher in patients when the
strategy of WACA was complemented by carina ablation. This is probably
due to the presence of pulmonary vein muscular fibers connecting
ipsilateral veins at the carina.30 31 Indeed first
pass isolation was achieved in all but two patients in whom empiric
carina ablation was added to the WACA and in one of the two patients
with residual PV electrograms the residual connection was located at a
site on the anterior ridge where the AI didn’t reach the target value of
515. Moreover, dormant PV-LA connections, revealed by adenosine
challenge, were mapped at the carina in all but one case. The presence
of dormant PV-LA connections at the carinas despite RF ablation this
area an ablation index between 415 and 515, and the need for additional
RF applications at this area, might be related to the epicardial nature
of the muscular sleeves connecting the ipsilateral PVs at the carina30 31.