Structured abstract
Introduction: A novel ablation catheter that can measure local
impedance (LI) was recently launched. We aimed to explore target LI
measurements at each radiofrequency application (RFA) for creating
sufficient ablation lesions during pulmonary vein (PV) isolation.
Methods: This prospective study included 15 consecutive
patients scheduled to undergo an initial ablation of paroxysmal atrial
fibrillation (AF). Circumferential ablation around both ipsilateral PVs
was performed using a 4-mm irrigated ablation catheter with an LI
sensor. Point-by-point ablation was used with a 4-mm
inter-ablation-point distance. Operators were blinded to LI measurements
during the procedure. Creation of sufficient ablation lesions was
assessed by the absence of a conduction gap.
Results: After first-pass encircling PV antrum ablation, left
atrium to PV conduction remained in 12 of 30 (40%) ipsilateral PVs.
Mapping using the mini-basket catheter identified 48 ablation points
through which the propagation wave entered the PV. At ablation points
with a gap, the LI drop during RFA was half that at points without a gap
(12 ± 7 vs. 23 ± 12 ohm, p<0.001). The GI drop did not differ
between ablation points with and without a gap (12 ± 7 vs. 14 ± 10 ohm,
p=0.10). An LI drop of 15 ohm predicted sufficient lesion formation
without a gap with a sensitivity of 0.71, specificity of 0.81, and
predictive accuracy of 0.75.
Conclusion: A target LI drop of 15 ohm at each RFA with a 4-mm
distance between adjacent ablation points may facilitate creation of
sufficient ablation lesions during PV isolation.
Key words; Local impedance, Radiofrequency ablation; Atrial fibrillation