Difference in radiofrequency ablation profile between during sinus rhythm and atrial fibrillation: Considerations in this era of high-power short-duration strategy

Background: The concept of ablation index (AI) was introduced to evaluate radiofrequency (RF) ablation lesions. It is calculated from power, contact force (CF), and RF duration. However, other factors may also affect the quality of ablation lesions. To examine the difference in RF lesions made during sinus rhythm (SR) and atrial fibrillation (AF). Methods: Sixty patients underwent index pulmonary vein isolation during SR (n = 30, SR group) or AF (n = 30, AF group). All ablations were performed with a power of 50 W, a targeted CF of 5-15 g, and AI of 400-450 using Thermocool Smarttouch SF. The CF, AI, RF duration, temperature rise (Delta temp), impedance drop (Delta imp), and the CF stability of each ablation point quantified as the standard deviation of the CF (CF-SD) were compared between the two groups. Results: A total of 3579 ablation points were analyzed, which included 1618 and 1961 points in the SR and the AF groups, respectively. Power, average CF, RF duration per point, and the resultant AI (389 +/- 59 vs. 388 +/- 57) were similar for the two rhythms. However, differences were seen in the CF-SD (3.5 +/- 2.2 vs. 3.8 +/- 2.1 g, p < .01), Delta temp (3.8 +/- 1.3 vs. 4.0 +/- 1.3(degrees)C, p < .005), and Delta imp (10.3 +/- 5.8 vs. 9.4 +/- 5.4 omega, p < .005). Conclusions: Despite similar AI, various RF parameters differed according to the underlying atrial rhythm. Ablation delivered during SR demonstrated less CF variability and temperature increase and greater impedance drop than during AF.