Residual impedance drop beyond ablation index is associated with atrial fibrillation recurrence after catheter ablation
S Yilmaz, E Kabayuka, P K Yanar, R KarabayirAbstract
Background
Ablation index (AI) is widely used to standardize radiofrequency energy delivery during atrial fibrillation (AF) ablation. However, AI is primarily a delivery-based metric and may not fully reflect real-time tissue response or lesion durability. Impedance drop directly reflects tissue heating and resistive changes during ablation. We hypothesized that the component of impedance drop not explained by AI—termed residual impedance drop—may better predict long-term AF recurrence.
Methods
We conducted a retrospective single-center study including 79 consecutive patients undergoing first-time catheter ablation for AF using a standardized high-power, short-duration protocol. Mean AI and impedance drop were recorded for anterior and posterior left atrial wall ablation sites. Residual impedance drop was calculated using linear regression models of impedance drop on AI, separately for anterior and posterior regions. The primary endpoint was AF recurrence occurring between 90 and 365 days after ablation. Associations with recurrence were assessed using Kaplan–Meier analysis and Cox proportional hazards models adjusted for age.
Results
During a median follow-up of 12 months, AF recurrence occurred in 13 patients (16.5%). Higher posterior residual impedance drop was strongly associated with reduced risk of first-year AF recurrence (adjusted hazard ratio 0.44, 95% confidence interval 0.28–0.70; p<0.001). Patients with posterior residual impedance drop above the median demonstrated significantly greater freedom from AF recurrence on Kaplan–Meier analysis. In contrast, mean posterior AI and anterior residual impedance drop were not independently associated with recurrence.
Conclusion
Residual impedance drop, particularly at the posterior left atrial wall, provides clinically relevant information beyond ablation index and is strongly associated with long-term AF freedom after high-power, short-duration ablation. These findings suggest that impedance-based metrics may better reflect effective lesion formation and could complement or refine current delivery-based ablation strategies.