Expandable Lattice Electrode Ablation Catheter A Novel Radiofrequency Platform Allowing High Current at Low Density for Rapid, Titratable, and Durable Lesions

BACKGROUND: High-current short-duration radiofrequency energy delivery has potential advantages for cardiac ablation. However, this strategy is limited by high current density and narrow safety-to-efficacy window. The objective of this study was to examine a novel strategy for radiofrequency energy delivery using a new electrode design capable of delivering high power at a low current density to increase the therapeutic range of radiofrequency ablation. METHODS: The Sphere9 is an expandable spheroid-shaped lattice electrode design with an effective surface area 10-fold larger than standard irrigated electrodes (lattice catheter). It incorporates 9 surface temperature sensors with ablation performed in a temperature-controlled mode. Phase I: in 6 thigh muscle preparations, 2 energy settings for atrial ablation were compared between the lattice and irrigated-tip catheters (low-energy: T-max 75 degrees C/5 s versus 25 W/20 s; high-energy: T-max 75 degrees C/7 s versus 30 W/20 s). Phase II: in 8 swine, right atrial lines were created in the posterior and lateral walls using low-and high-energy settings, respectively. Phase III: the safety, efficacy, and durability at 30 days were evaluated by electroanatomical mapping and histopathologic analysis. RESULTS: In the thigh model, the lattice catheter resulted in wider lesions at both low-and high-energy settings (18.7 +/- 3.3 versus 12.2 +/- 1.7 mm, P<0.0001; 19.4 +/- 2.4 versus 12.3 +/- 1.7 mm, P<0.0001). Atrial lines created with the lattice were wider (posterior: 14.7 +/- 3.4 versus 9.2 +/- 4.0 mm, P<0.0001; lateral: 15.8 +/- 4.2 versus 5.7 +/- 4.2 mm, P<0.0001) and required 85% shorter ablation time (12.4 versus 79.8 s/cm-line). While current squared (I2) was higher with Sphere9 (7.0 +/- 0.04 versus 0.2 +/- 0.002 A(2); P<0.0001), the current density was lower (9.6 +/- 0.9 versus 16.9 +/- 0.09 mA/mm(2); P<0.0001). At 30 days, 100% of ablation lines created with the lattice catheter remained contiguous compared with only 14.3% lines created with a standard irrigated catheter. This was achieved without steam pops or collateral tissue damage. CONCLUSIONS: In this preclinical model, a novel, high-current low-density radiofrequency ablation strategy created contiguous and durable ablation lines in significantly less ablation time and a comparable safety profile.