Atrial myocardial substrate has a significant influence on local impedance data - clinical experience from high power short duration and standard radio frequency ablations

Abstract Funding Acknowledgements Type of funding sources: None. Background Local impedance is a new clinically used RF ablation parameter used to predict RF lesion creation. By now, data about the influence of atrial substrate on local impedance is still scarce. The aim of this study was to investigate local impedance data of different atrial tissues (healthy myocardium vs. Low Voltage areas) and the importance of local impedance drops during HPSD and standard RF ablation in atrial tissue. Methods A total of n=1319 clinical RF applications in n=51 clinical left atrial ablation procedures were analyzed regarding underlying RF ablation parameters (RF power, duration, contact force, global and local impedance data). 3D mapping data were used to differentiate RF ablations in low voltage areas (<=1.0mv) from those in healthy atrial myocardium (>1.0mV). Local and global impedance baseline values and drops, RF electrogram amplitude attenuation, as well as RF data were calculated and registered for statistical analysis. Results Local impedance drops were significantly higher during RF application in healthy myocardium when compared to low voltage areas (18,6 vs. 16,6 Ohm, p<0.01). Baseline local impedance was significantly higher in healthy atrial myocardium when compared to low voltage areas (105,4 vs. 99,1 Ohm, p<0.01). There was no significant difference in global impedance values between low voltage areas and healthy atrial myocardium (p=0.34). These findings were confirmed in HPSD (60W, 10s) as well as in standard (30-40W, 30-60s) RF applications. Impedance drops were significantly larger in HPSD when comapred to standard RF ablation (p<0.01). Detailed boxplot results are presented in the Figure. Conclusions Local impedance drop is a good predictor of RF lesion creation in HPSD as well standard RF ablations. Interestingly, different local impedance but not global impedance values were observed in healthy and low voltage areas. In clinical practice, local impedance may be a useful parameter to identify atrial substrate.