Design of a Conductive Hydrogel Coating to Improve Catheter–Tissue Coupling in Radiofrequency Ablation

Figures

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  Figure 1.. Fabrication of the ablation catheter coating. The hydrogel coating was covalently crosslinked directly onto the catheter tip using TMSPMA functionalization. a) First, the catheter tip was cleaned with ethanol, acetone, and DI water and then dried for one hour. b) Oxygen plasma was used to modify the metal’s surface with hydroxyl groups. c) The catheter tip was then soaked in a 10% TMSPMA in ethanol for 1 hour. d) Finally, the catheter was removed from the TMSPMA solution, rinsed in ethanol, dried with nitrogen gas, and submerged in the hydrogel precursor solution using a tapered mold prior to curing with UV light (365nm) for 4 minutes.

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  Figure 2.. Hydrogel coating durability. Stereoscope images of 20% 10kDa PEUDAm catheter coating before and after a) drying, Ethylene Oxide (EtO) sterilization, and swelling to equilibrium in DI water, b) 50 cycles of radiofrequency ablation at 30W, and c) introducer sheath deployment. n = 3 for each composition.

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  Figure 3.. Effect of hydrogel coating thickness on contact area. a) Catheter diameter before and after swelling to equilibrium; b) contact area between ablation catheter and atrial tissue mimic, as determined by arc length analysis; c) images of ablation catheter contact with atrial tissue, 20 g contact force. Data for all comparisons represent individual data points, means, and standard deviations of each specimen (n = 3 for each composition, 3 compositions). Significant differences between groups are marked as follows: *** p < 0.0002.

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  Figure 4.. Effect of hydrogel coating stiffness on tissue coupling. Hydrogel coatings with compositions of 10% 20kDa PEUDAm, 20% 10kDa PEUDAm, and 30% 3.4kDa PEUDAm. a) hydrogel stiffness in comparison to atrial stiffness (n = 3 for each composition, 3 compositions); b) probe diameter across hydrogel compositions and bare metal (n = 9); c) contact area between ablation catheter and atrial tissue mimic, as determined by arc length analysis; d) images of ablation catheter contact with atrial tissue, 20 g contact force. Data for all comparisons represent individual data points, means, and standard deviations of each specimen (n = 6 for each composition, 3 compositions). Significant differences between groups are marked as follows: * (p < 0.05), ** (p < 0.001), *** (p < 0.0002), **** (p < 0.0001).

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  Figure 5.. Effect of hydrogel-mediated ablation on lesion geometry at 30W. a) Setup to carry out ex vivo ablation on ventricular free wall. Nonviable tissue presents as light brown while viable tissue is stained bright red. b) Ex vivo lesion widths compared to a standard ablation catheter at 30W. e) Ex vivo lesion depths compared to a standard ablation catheter at 30W. Data for all comparisons represent individual data points, means, and standard deviations of each specimen (n = 3 for each composition, 3 compositions). Significant differences between groups are marked as follows: * (p < 0.05), ** (p < 0.001), *** (p < 0.0002), ****(p < 0.0001), ns (p > 0.05).

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  Figure 6.. Effect of hydrogel-mediated ablation on lesion geometry and safety at increased ablation power. a) Representative lesions formed by bare metal and hydrogel-coated catheters at 50W, demonstrating increase in lesion dimensions at increased power and tissue cavitation due to steam pop for the bare metal catheter ablation (scale bar is 10 mm). b) comparison of ablation power (30W vs 50W) on ex vivo lesion width. c) comparison of ablation power (30W vs 50W) on ex vivo lesion depth. Data for all comparisons represent individual data points, means, and standard deviations of each specimen (n = 3 for each composition, 3 compositions). Significant differences between groups are marked as follows: ** (p < 0.001), *** (p < 0.0002). X indicates no lesion formation.

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  Figure 7.. Effect of hydrogel conductivity on coating durability at higher ablation power. Stereoscope images of hydrogel-coated catheters before and after 50 cycles of 50W ablation with a) 20% 10kDa PEUDAm coating swelled in 0.9% saline with a hydrogel conductivity of ~10 mS/cm and b) 20% 10kDa PEUDAm coating swelled in 2.0% saline with a hydrogel conductivity of ~15 mS/cm.

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  Figure 8.. Thermochromic atrial tissue mimic as an analog for ex vivo ablation. a) Images of tissue mimic with “nonviable” tissue turning white after ablation and “viable” tissue remaining black; b) comparison of ex vivo vs thermochromic tissue mimic lesion width; c) comparison of ex vivo vs thermochromic tissue mimic lesion depth. Data for all comparisons represent individual data points, means, and standard deviations of each specimen (n = 6). Significant differences between groups are marked as *** p < 0.0001, ns indicates no significant differences, p > 0.05.