Discussion
Permanent PVI and freedom from AF recurrence are contingent upon efficient and durable RF lesion formation 22,23. The amount of RF energy delivered to the tissue during ablation plays a central role in lesion durability 24. Good energy coupling from the ablation catheter to the cardiac tissue requires stable catheter-tissue contact with sufficient CF during RF application25. Catheter stability, adequate CF and maximum time spent in the desired contact force range have been correlated with reduced PV reconnection and improved RF ablation outcomes11,21,26. Use of steerable sheaths has improved procedural outcomes in comparison to conventional sheaths due to the ease of manipulation, access and contact with target sites14,19. The rigid make up of steerable sheaths, also, reduces the effects of cardiac and respiratory excursions and provide better catheter control 23. Several steerable sheaths are commercially available but their relative influence on CF and catheter stability remains unknown. In this study, retrospective evaluation of data from 30 cases performed using two different steerable sheaths indicated that procedural efficiency measures such as CF stability and RF time per lesion may be impacted by the choice of sheath. A consistent ablation strategy was used whereby pulmonary veins were ablated in sequence, with the left veins before the right veins, suggesting that any observed trends are attributed to both anatomy and/or sheath fatigue over time.
Both steerable sheaths in this study achieved similar mean CF, ruling out potential procedural bias. However, it has become evident that catheter and CF stability may play more important roles in forming effective lesions with lower reconnection rates than CF magnitude alone4. In this case series, the SureFlex sheath maintained an overall 13% greater CF stability than the Agilis sheath, with similar trends in each pulmonary vein.
In studies targeting a CF of approx. 20g, it was found that maintaining a minimum CF of 10g for at least 80% of the individual RF application time was necessary for effective lesions and significantly improved overall ablation outcomes 15,21. In contrast, RF application with insufficient tissue CF has been correlated with inadequate lesion formation 26-28 and higher rate of AF recurrence 21,22,29. Since a higher power ablation protocol was used in the present study, a lower target CF (10-15g) and minimum threshold for catheter tissue contact (5g) were defined27. The SureFlex sheath led to significantly fewer lesions with poor contact (<5g for more than 80% of the ablation time). This trend was further pronounced in the right inferior and superior PVs, which are typically more difficult to navigate.
Reduced CF stability may necessitate longer RF application time in order to reach the desired lesion endpoint and acute success4,24. This not only reduces overall efficiency and prolongs procedure time but, also, increases the risk of coagulum formation and steam pops due to excessive RF application28,30. In this study, RF time per lesion was 12% shorter in the SureFlex group than Agilis, suggesting improved RF delivery and procedural efficiency. To our knowledge, this is the first study that compares the procedural performance of two commercially available sheaths with the goal of improving CF stability for more effective RF ablations. Preliminary data from follow-up visits suggests fewer patients in the SureFlex group remained on anti-arrhythmic drugs at 6 months post-ablation than in the Agilis group; however, this did not reach significance.