Background:

Several parameters are assumed to influence lesion size in RF ablation. Especially RF power, duration and contact force are considered for optimizing lesion quality and creating durable lesions. Recent data showed a significant influence of electrode-tissue-coupling (ETC) on lesion size and occurrence of steam pops. Therefore, this study aimed to investigate the impact of ETC and contact force on lesion progression in RF ablation.

Methods:

RF-lesions were created using the IntellaNav StablePoint catheter in an ex vivo porcine cardiac model. The experimental setup consisted of a saline-filled container, a dispersive electrode, a heated thermostat and a circulation pump to imitate in vivo conditions. Global impedance was kept at 120 Ohm as well as the temperature at 37°C. RF power of 20W, 30W, 40W, and 50W was used. The ETC levels (full/minor) and CF-level (0-5g, 10-15g and 20-25g) were systematically varied between minor and full coupling. In minor ETC-level, only the distal end of the catheter is in contact with the tissue. In full ETC-level, the whole catheter tip is in contact with the tissue. All parameters (power, temperature, global and local impedance, contact force, ETC, lesion size) were measured constantly during application of RF-current, enabling real-time correlation of RF parameters and lesion size. In case of an audible steam pop, RF application was stopped.

Results:

8654 measurements out of 72 lesions were included in analysis. Significant differences in lesion size were observed when ETC-level was differed. Lesion depth was significantly higher in full ETC-level (5.13 ± 0.99 mm vs. 9.45 ± 1.45 mm, p<0.001). No significant difference was seen in lesion diameter and depth by varying CF-level, when lesions were created in full ETC-level (Table 1). These findings are also illustrated in Figure 1.

Conclusion:

ETC is a main predictor of lesion size in RF-ablation. CF also influences lesion depth and diameter. However, significant differences were only observed in minor ETC-levels. Consequently, CF might be a main factor for durable lesions in RF-ablation, but the influence of varied CF decreases when ETC-level is rising.