Background: Ventricular tachycardia ablation is often limited by insufficient lesion creation. A novel radiofrequency catheter with an expandable lattice electrode has a larger surface area capable of delivering higher currents at a lower density to potentially increase lesion dimensions without overheating. Methods: This 8F bidirectional irrigated catheter (Sphere-9, Affera Inc) has a 9 mm spherical lattice tip ("lattice") with an effective surface area 10-fold larger than standard linear catheters. Nine surface thermocouples provide temperature feedback to a proprietary high-current generator operating in a temperature-controlled mode. Ex vivo phase: in 11 bovine hearts, unipolar ablation at 30, 60, and 120 seconds was compared between the lattice (Tmax60°C) and a standard linear irrigated-tip catheter (40 W) at contact force of 10 g. In 5 porcine hearts, bipolar ablation was compared between the catheters (Tmax60°C versus 40 W; 60 seconds). In vivo phase: in 9 swine, ventricular ablation at Tmax60°C versus 40 W was performed for 60 seconds. In addition, direct tissue temperature at 3- and 7-mm tissue depth was measured in a thigh muscle preparation. Results: Ex vivo: lattice produced deeper lesions at 30, 60, and 120 seconds application duration (6.7±1.3 versus 4.8±1.2 mm; 8.3±1.4 versus 5.4±0.8 mm; 10.0±1.6 versus 6.1±1.6 mm, respectively, P≤0.001 for all). Bipolar lesions were deeper (15.8±4.1 versus 10.5±1.4 mm, P<0.001) and more likely to be transmural (80% versus 0%, P=0.002). In vivo: lattice produced deeper lesions (10.5±1.4 versus 6.5±0.8 mm, P≤0.001). Tissue temperature at 7 mm was higher with the lattice (+15.1±2.4°C; P<0.001). The steam-pop occurrence was lower with the lattice (total: 4% versus 18%, P=0.02; in vivo 0% versus 14.2%, P=0.13). Conclusions: This novel radiofrequency system produces larger ventricular lesions compared with standard irrigated catheters and at a lower risk of tissue overheating. This may improve the efficacy of ventricular tachycardia ablation procedures while reducing the number of applications and procedural duration.
- heart ventricle