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.