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.