Nkansah, A. | Search bioRxiv

bioRxiv2023

Eliminating steam pops and improving lesion safety in atrial ablation with conductive hydrogels

BackgroundAtrial fibrillation (AF) is a significant burden worldwide, and the existing treatments leave much to be desired. There are, however, opportunities to improve the safety and efficacy of the most popular treatment, radiofrequency (RF) cardiac ablation, using conductive hydrogels as an ablation mediator. MethodsLesions were created in ex vivo ventricular tissues using bare metal traditional RF catheters and three different hydrogels with varying conductivities to assess the effect of conductivity on lesion formation. Similar procedures were performed in atrial/esophageal tissue stacks to mimic physiological AF ablation and demonstrate the initial safety profile of conductive hydrogel-mediated ablation. ResultsThe hydrogel mediated lesions were overall shallower and narrower than bare metal, and also exhibited less char and improved lesion homogeneity. The hydrogel also eliminated steam pops. Finally, the hydrogel appeared to be more thermally protective of the esophagus in the atrial/esophageal tissue stack, greatly reducing the lesion formation on the esophagus while still achieving transmural lesions in the atrial tissue. ConclusionsHydrogel-mediated RF ablation holds promise as a novel method to improve ablation outcomes for AF patients. Future work will confirm this in vivo and establish the chemistry required to create a conductive hydrogel coating for RF ablation catheters.

bioengineering↗

bioRxiv2023

Hydrogel-Polyurethane Fiber Composites With Enhanced Microarchitectural Control For Heart Valve Replacement

Polymeric heart valves offer the potential to overcome the limited durability of tissue based bioprosthetic valves and the need for anticoagulant therapy of mechanical valve replacement options. However, developing a single-phase material with requisite biological properties and target mechanical properties remains a challenge. In this study, a composite heart valve material was developed where an electrospun mesh provides tunable mechanical properties and a hydrogel coating confers an antifouling surface for thromboresistance. Key biological responses were evaluated in comparison to glutaraldehyde-fixed pericardium. Platelet and bacterial attachment were reduced by 38% and 98%, respectively, as compared to pericardium that demonstrated the antifouling nature of the hydrogel coating. There was also a notable reduction (59%) in the calcification of the composite material as compared to pericardium. A custom 3D printed hydrogel coating setup was developed to make valve composites for device-level hemodynamic testing. Regurgitation fraction (9.6 {+/-} 1.8%) and effective orifice area (1.52 {+/-} 0.34 cm2) met ISO 5840-2:2021 requirements. Additionally, the mean pressure gradient was comparable to current clinical bioprosthetic heart valves demonstrating preliminary efficacy. Although the hemodynamic properties are promising, it is anticipated that the random microarchitecture will result in suboptimal strain fields and peak stresses that may accelerate leaflet fatigue and degeneration. Previous computational work has demonstrated that bioinspired fiber microarchitectures can improve strain homogeneity of valve materials toward improving durability. To this end, we developed advanced electrospinning methodologies to achieve polyurethane fiber microarchitectures that mimic or exceed the physiological ranges of alignment, tortuosity, and curvilinearity present in the native valve. Control of fiber alignment from a random fiber orientation at a normalized orientation index (NOI) 14.2 {+/-} 6.9% to highly aligned fibers at a NOI of 85.1 {+/-} 1.4%. was achieved through increasing mandrel rotational velocity. Fiber tortuosity and curvilinearity in the range of native valve features were introduced through a post-spinning annealing process and fiber collection on a conical mandrel geometry, respectively. Overall, these studies demonstrate the potential of hydrogel-polyurethane fiber composite as a heart valve material. Future studies will utilize the developed advanced electrospinning methodologies in combination with model-directed fabrication toward optimizing durability as a function of fiber microarchitecture.

bioengineering↗