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CA-530-01 USE THE FORCE: ADEQUATE CATHETER CONTACT FORCE IS CRITICAL FOR HIGH QUALITY LESIONS GUIDED BY ABLATION INDEX

      Background

      Ablation Index (AI) is a measure used to estimate lesion size based on power, contact force (CF), and lesion duration. Ideally, AI-guided titration of lesion duration corrects for variations in contact force. Impedance drop is a validated measure that correlates well with lesion formation. Therefore, analysis of the relationship between AI, CF, and impedance drop may offer insight into possible residual influences of CF on lesion formation.

      Objective

      To investigate and characterize the impact of CF on impedance drop during AI-guided ablation.

      Methods

      We retrospectively reviewed atrial fibrillation ablation cases (AFAs) performed at a single center. We examined the correlation between CF and Impedance drop within narrow ranges of AI (17 groups). In a secondary analysis, we matched lesion pairs with high and low CF (< 10 g and > 20 g) for stability, AI, lesion location, and power. Matched pairs were compared using a t-test.

      Results

      There were 13444 lesions with AI between 320 and 530 from 91 AFAs. For lesions that had a low AI (< 402.3), we observed mostly no residual correlation between contact force and impedance drop ( Fig 1). For lesions with high AI (> 402.3), we observed a consistent significant correlation between CF and impedance drop (Fig 1).
      In the matched sample, the high CF group had a greater impedance drop when compared to the low CF group: 8.5 ±5.3 vs 7.0 ±4.0 Ohms p < 0.01 (Figure 2), despite having similar AI. When examining the subset of matched pairs with AI < 400, we observed no significant difference in impedance drop between the high and low CF groups: 6.7 ±4.7 vs 6.5 ±4.1 Ohms (p = 0.6). When examining the matched pairs with AI > 400, we again observed a significant difference: 9.8 ±5.3 vs 7.3 ±3.9 Ohms p < 0.01 (Fig 2).

      Conclusion

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      Figure 2: A plot of impedance drop by CF group in AI matched pairs. A significant difference is seen for the overall sample and pairs with AI > 400.