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.

Department of Cardiology Hamolka Hospital Prague Czech Republic

Harvard Thorndike Electrophysiology Institute Cardiovascular Division Department of Medicine Beth Israel Deaconess Medical Center Harvard Medical School Boston MA

Helmsley Center for Electrophysiology Department of Cardiology Icahn School of Medicine at Mount Sinai NY

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