Does the same lesion index mean the same efficacy and safety profile: influence of the differential power, time, and contact force on the lesion size and steam pops under the same lesion index.

BACKGROUND: The lesion index (LSI) helps predict the lesion size and is widely used in ablation of various types of arrhythmias. However, the influence of the ablation settings on the lesion formation and incidence of steam pops under the same LSI value remains unclear. METHODS: Using a contact force (CF) sensing catheter (TactiCath™) in an ex vivo swine left ventricle model, RF lesions were created with a combination of various power steps (30 W, 40 W, 50 W) and CFs (10 g, 20 g, 30 g, 40 g, 50 g) under the same LSI values (5.2 and 7.0). The correlation between the lesion formation and ablation parameters was evaluated. RESULTS: Ninety RF lesions were created under a target LSI value of 5.2, and eighty-four were developed under a target LSI value of 7.0. In the LSI 5.2 group, the resultant lesion size widely varied according to the ablation power, and a multiple regression analysis indicated that the ablation energy delivered was the best predictor of the lesion formation. To create a lesion depth > 4 mm, an ablation energy of 393 J is the best cutoff value, suggesting a possibility that ablation energy may be used as a supplemental marker that better monitors the progress of the lesion formation in an LSI 5.2 ablation. In contrast, such inconsistency was not obvious in the LSI 7.0 group. Compared with 30 W, the 50-W ablation exhibited a higher incidence of steam pops in both the LSI 5.2 and 7.0 groups. CONCLUSIONS: The LSI-lesion size relationship was not necessarily consistent, especially for an LSI of 5.2. To avoid any unintentional, weak ablation, the ablation energy may be a useful supportive parameter (393 J as a cutoff value for a 4-mm depth) during ablation with an LSI around 5.2. Thanks to a prolonged ablation time, the LSI-lesion size relationship is consistent for an LSI of 7.0. However, it is accompanied by a high incidence of steam pops. Care should be given to the ablation settings even when the same LSI value is used.

Detailed analysis of the lesion formation using a diamond tip catheter in an ex vivo experimental model.

BACKGROUND: A novel Diamond Temp™ (DT; Medtronic, Minneapolis, MN, USA) catheter has enabled performing a surface temperature-controlled ablation. The chemical vapor deposition diamond of the ablation catheter acts as a thermal radiator and is useful for effective cooling of the ablation catheter tip. However, a detailed analysis of the lesion formation with this catheter remains unknown. METHODS: DT catheters were used in an excised swine heart experimental model. A cross-sectional analysis of 60-s lesions [a combination of various energy power settings (30, 40, and 50 W), and various contact forces (CF) (10, 30, and 50 g)] and a longitudinal analysis [a combination of various powers (40 W or 50 W), various CFs (10, 30, and 50 g), and various ablation times (5 s, 10 s, 15 s, 20 s, 25 s, 30 s, and 60 s)] of the DT catheter were analyzed. RESULTS: The maximum lesion depth, maximum diameter, and lesion volume with a 10 g ablation were significantly lower than those with a 30 g or 50 g ablation. There were no significant differences in the lesion formation between the 30 g ablation and 50 g ablation under each radiofrequency (RF) power setting. The impedance drops with steam pops were significantly greater than those without steam pops (pop (+) vs. pop (-), 26.2 ±â€¯6.6 Ohm vs. 18.4 ±â€¯7.1 Ohm, p = 0.0001). A non-linear, time-dependent increase in the lesion depth and diameter was observed for all power and CF settings. Comparing the lesion depth and diameter between 40 W and 50 W under the same CF setting and same ablation time, most of the settings had no significant difference. CONCLUSION: Ablation lesions created with the DT catheter were similar to other catheters. Similar ablation lesions were created with the 40 W or 50 W ablation under the same CF setting and same ablation time. Regardless of the ablation power, monitoring the general impedance during the RF application was indispensable for a safe procedure.