Fehmi Keçe

Chapter 7 152 7.4 Discussion 7.4.1 Main Findings The purpose of this study was to identify procedural and biophysical parameters associated with the absence of early reconnection and dormant pulmonary vein conduction (ERC) during AF ablation with the cryoballoon. We found that unsuccessful freeze attempts, a longer time-to-isolation and a higher (warmer) nadir balloon temperature were associated with ERC. Based on these parameters, we constructed an easy-to-use table which may help to decide for or refrain from a 30-min waiting period followed by adenosine testing. 7.4.2 Prognostic significance of dormant conduction Adenosine testing to reveal and subsequently treat dormant conduction during AF ablation is associated with lower recurrence rates (5, 9). An international multicentre randomised study showed an improvement of arrhythmia-free survival using this strategy compared to no-adenosine-testing, with an absolute risk reduction of 27% and a hazard ratio of 0.44 (p<0.0001) (5). In addition, applying a waiting period before adenosine testing also appears to be an important tool to detect impending PV reconnections (10). We previously could demonstrate that the incidence of dormant conduction was higher after a waiting period of 30 minutes than immediately after PVI. In this study, additional applications for the treatment of dormant conduction resulted in an improved 1-year AF-free survival(4). In the current study a comparable outcome between groups with and without ERC was observed after 1 year, regardless of the number of unsuccessful attempts, lower balloon temperatures and longer time-to-isolation in the PV. Again this suggests the effectiveness of treating ERC after a waiting period followed by adenosine testing. The prevalence of dormant conduction can be influenced by the duration of the cryo-application(2). In a prior study, we could show that increasing the duration of the cryo-application from 90 to 150 seconds after acute PV isolation, resulted in a decreased incidence of dormant conduction from 22% to 4% of the veins (2). In the current study, we could demonstrate that dormant conduction after 30 minutes was more prevalent in veins in which more than one cryo-application had to be performed to achieve isolation. This may be explained by anatomical properties of the PV ostium causing insufficient PV occlusion and incomplete balloon-tissue contact. Another explanation might be related to the occurrence of oedema after the first application, making a second application less effective (11, 12). However, although tissue oedema (diffuse wall thickening of the antra