Abstract 1785: Determinants of the Lesion Size Created using a Novel Saline-Injection Radiofrequency Ablation Catheter in the Canine Heart
Background: Conventional RF ablation of the LV has been unreliable in creating transmural lesions, despite active irrigation tip cooling. Alternatively, saline-injection radiofrequency ablation incorporating a 6 mm, 20-Ga needle tip to create a virtual electrode within the tissue may create larger lesions than conventionally possible. The predictors of this large lesion size, however, have not been established.
Methods: Eight dogs underwent ablation in the left ventricle with the catheter introduced via the right carotid artery. The ablations were randomly irrigated with normal saline at a flow of 5 or 10 mL/sec, a target temperature of 40, 50, or 60 °C, and with a maximum power of 30, 40, 50, or 60 W for 60 or 120 seconds. Lesion dimensions were assessed at pathologic exam.
Results: Sixty-three lesions were created with an average of 7.8 ± 3.2 per dog. Fifty-one percent of lesions were full thickness. Lesion areas were injectate temperature-dependent with lesion areas of 130 ± 66 mm2, 258 ± 146 mm2, 288 ± 174 mm2 for 40, 50, and 60 °C, respectively (p<0.05 for 40 °C vs. 50 °C and 60 °C). Lesion depth was 12±2 mm at 40 °C, 13±3 mm at 50 °C, and 15±4mm at 60 °C (p<0.05 for 40 °C vs. 60 °C). Lesion areas were power-dependent with lesion areas of 119±14 mm2, 216±149 mm2, 226 ± 76 mm2, 469 ± 181 mm2 for 30, 40, 50, and 60 W, respectively (p<0.05 for all except 40 W vs. 50 W). Lesion depth changed less between groups (12 ± 3 mm at 30 W, 14 ± 3 mm at 40 W, 13 ± 1mm at 50 W, 15 ± 4mm at 60 W, p=ns for each). Using multivariate regression analysis, lesion size remained dependent on power and injectate temperature, but not saline flow and ablation time. Correlations were as follows: (Depth: power: B =0.29, p = 0.1; injectate temperature: B = 0.33, p < 0.05; Area: power: B = 0.35, p < 0.05; injectate temperature: B = 0.41, p < 0.05).
Conclusions: In this evaluation, lesion size created by catheter-based, virtual electrode ablation was both power and temperature dependent. This information is useful for titrating energy delivery for achieving desired VT ablation outcomes, without excessive tissue destruction.