Introduction
While radiofrequency (RF) catheter ablation for atrial fibrillation (AF)
is associated with acute pulmonary vein isolation (PVI) in over 90% of
cases, long-term success of a single ablation for paroxysmal AF has been
reported to be 69% at one year 1 and only 54% beyond
three years 2. Long-term PVI success, defined by the
reduced rate of AF recurrence, is largely driven by the durability, as
well as continuity and transmurality of formed lesions3. Acute lesion assessment is based on impedance drop
from baseline, change in electrogram amplitude or morphology, change in
pacing threshold and/or real-time MRI, while overall procedural success
is confirmed in terms of PVI. Durability of RF lesions has been
associated with the amount of RF energy delivered. Insufficient RF
delivery leads to PV reconnection and prolonged procedure times, while
excessive RF application may lead to complications such as esophageal
injury, atrial perforation, steam pops and coagulum formation4-6. The relative RF energy received by the tissue
and, consequently, lesion quality, are dependent on consistent coupling
between the ablation catheter tip and the target tissue4,7, which can be compromised by small inadvertent
movements during the procedure 8. Efforts to improve
catheter-tissue contact and stability include the use of high-frequency
jet ventilation to minimize respiratory excursion, high rate pacing to
regulate cardiac contractions, electroanatomic mapping to monitor
catheter proximity and tissue contact, as well as sheath and catheter
selection 9-14. Introduction of contact force
(CF)-sensing ablation catheters has allowed real-time measurement of
catheter-tissue contact to guide RF delivery and formation of more
effective lesions 7. The use of CF-sensing catheters
has reduced procedure time and fluoroscopy usage, and improved the
1-year AF recurrence rate by up to 12% compared to non-CF sensing
catheters 15-17. The adoption of steerable sheaths in
PVI procedures has not only improved catheter manipulation and access to
target sites 14,18,19 but, also, improved procedural
CF. In randomized studies, steerable sheaths significantly enhanced CF
stability, facilitated mapping and ablation, reduced procedure times and
improved procedural efficiency when compared to standard fixed curve
sheaths 20. Improvements in CF using steerable sheaths
were further noted in different locations in the left atrium (LA). While
accessing the left superior and inferior pulmonary veins requires a
relatively straight sheath trajectory, the right superior and inferior
pulmonary veins require greater sheath manipulation with tight angles of
curvature and stabilization to maintain catheter tip position at the
desired location 14. Steerable sheaths have also been
shown to have fewer lesions with insufficient tissue CF15,21; the reduction of these poor CF lesions has been
associated with improved freedom from recurrence at one year21. In an effort to optimize catheter stability during
PVI procedures, the present study compares whether CF and procedural
efficiency can be further improved using different
commercially-available steerable sheaths.