Novel Irrigated Temperature-Controlled Lattice Ablation Catheter for Ventricular Ablation

Abstract

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.

Pulsed Field Ablation Using a Lattice Electrode for Focal Energy Delivery

“…The system also provides an indication of proximity between the catheter and the tissue by continuously evaluating impedance between each of the mini-electrodes and the center electrode, highlighting electrodes with elevated local impedance. 9,10 The center of the lattice contains a protected irrigation nozzle with micropores that provide homogeneous cooling unaffected by pressure applied to the catheter or the angle of tissue engagement.…”

“…In preclinical studies, it produced rapid and durable atrial lesions, and ventricular lesions with a maximal depth that was twice of standard irrigated catheters. 9,10 In humans, this technology produced rapid and durable PVI with a similar safety profile to other RF technologies. 11,12 However, given the potential safety benefits of PFA, we sought to develop a system that can deliver either focal RFA or PFA using the same catheter.…”

Effect of Baseline Impedance in Radiofrequency Delivery on Lesion Characteristics and the Relationship Between Impedance and Steam Pops

“…However, they changed the baseline R by adjusting the series R in the circuit instead of changing the R of normal saline in the container. Shapira-Daniels et al changed the contact area between the negative plate and the skin (the parallel circuit reduces the impedance), so as to achieve the purpose of reducing the impedance ( 15 ). As a result, they found the opposite pattern that this study found: RFCA at a lower R resulted in increased tissue heating and led to larger lesion dimensions because of the increased current delivery ( 1 ).…”

Development of a clinically relevant ex vivo model of cardiac ablation for testing of ablation catheters

“…To develop a robust ex vivo model with physiological and clinical relevance, an RCA was conducted to isolate potential parameters influencing cardiac ablation outcomes based on prior model development and physiology literature. 5,[9][10][11][12][13][14][15][16][17][18][19][20][21][22][23] Model parameters were subdivided into three categories: ex vivo tissue parameters, media parameters, and impedance parameters. Each parameter was identified alongside its mechanism of influencing ablation outcomes (Central Illustration).…”