Ablation Index and Surround Flow Catheter Irrigation: Impedance-Based Appraisal in ClinicalAblation.

Abstract

This study sought to assess the impact of ablation power and catheter irrigation during clinical radiofrequency ablation using impedance drop. In preclinical studies, ablation power and catheter irrigation are determinants of ablation efficacy. Static 30-s left atrial ablations were delivered in patients undergoing their first atrial fibrillation ablation. Impedance drop during ablation (as a measure of efficacy) was compared using the following: the force time integral (FTI); the FTI-P (a cumulative multiple FTI and ablation power), and ablation index (AI), a weighted algorithm including contact force, power, and duration. Comparison was also made between a conventionally irrigated (SmartTouch [ST]) versus surround flow (STSF) contact force-sensing catheter. We analyzed 1,013 ablations. For both catheters, the Spearman correlation was higher between impedance drop and AI (rho= 0.89 ST, 0.84 STSF) than FTI-P (rho= 0.71 ST, 0.53 STSF) or FTI (rho= 0.77 ST, 0.52 STSF); p<0.0005 for each. STSF ablations had lower minimum catheter tip temperatures (25°C [interquartile range (IQR): 25°Cto 27°C] vs. 35°C [IQR: 34°C to 36°C]; p< 0.005), and lesser impedance drop per FTI or AI (p< 0.005 for both). ForSTSF, impedance drop plateaued sooner than for ST with respect to FTI (184g.s vs. 463g.s) and AI (370AIvs. 430AI). AI is a more complete ablation descriptor than is FTI or FTI-P, reflected by a stronger correlation withimpedance drop. STSF ablations have lower impedance drop per AI or FTI than ST ablations do, suggesting differenttargets should be used if ablating guided by impedance drop with STSF. With ST, ablation beyond 430 AIprovides minimal additional biophysical efficacy, suggesting an upper limit to use for clinical ablation.