In Vivo Restoration of Myocardial Conduction With Carbon Nanotube Fibers

Abstract

Background: Impaired myocardial conduction is the underlying mechanism for re-entrant arrhythmias. Carbon nanotube fibers (CNTfs) combine the mechanical properties of suture materials with the conductive properties of metals and may form a restorative solution to impaired myocardial conduction. Methods: Acute open chest electrophysiology studies were performed in sheep (n=3). Radiofrequency ablation was used to create epicardial conduction delay after which CNTf and then silk suture controls were applied. CNTfs were surgically sewn across the right atrioventricular junction in rodents, and acute (n=3) and chronic (4-week, n=6) electrophysiology studies were performed. Rodent toxicity studies (n=10) were performed. Electrical analysis of the CNTf-myocardial interface was performed. Results: In all cases, the large animal studies demonstrated improvement in conduction velocity using CNTf. The acute rodent model demonstrated ventricular preexcitation during sinus rhythm. All chronic cases demonstrated resumption of atrioventricular conduction, but these required atrial pacing. There was no gross or histopathologic evidence of toxicity. Ex vivo studies demonstrated contact impedance significantly lower than platinum iridium. Conclusions: Here, we show that in sheep, CNTfs sewn across epicardial scar acutely improve conduction. In addition, CNTf maintain conduction for 1 month after atrioventricular nodal ablation in the absence of inflammatory or toxic responses in rats but only in the paced condition. The CNTf/myocardial interface has such low impedance that CNTf can facilitate local, downstream myocardial activation. CNTf are conductive, biocompatible materials that restore electrical conduction in diseased myocardium, offering potential long-term restorative solutions in pathologies interrupting efficient electrical transduction in electrically excitable tissues.

Nanomaterials for Cardiac Tissue Engineering

“…Unique from the aforementioned studies, CNTs have also been evaluated in vivo using models other than myocardial infarction models. In one recent study, McCauley et al ablated the atrioventricular nodes of sheep models, and CNT fibers were sutured across the scars created by this process [68]. Although this study with CNT fibers did not involve cardiac tissue engineering per se, it did demonstrate that the electrical conductivity of CNTs could be quite helpful in damaged cardiac tissue.…”

Cardiac mechanostructure: Using mechanics and anisotropy as inspiration for developing epicardial therapies in treating myocardial infarction

“…Behabtu et al developed a wet spinning technique to create macroscopic carbon nanotube fibers, which can be sewn across the epicardial scar and electrically paced [ 270 ]. Testing of this design in ovine models showed improve conduction velocity over the scar area [ 271 ]. Additionally, Park et al developed a styrene-butadiene-styrene polymer with silver nanowires mesh.…”

Nano-Medicine in the Cardiovascular System

“…These 3D printed patches were shown to not only improve conduction velocities of damaged canine ventricular tissue post-implantation, but to restore them to baseline (∼24-25 cm/s) as noted prior to surgical disruption. CNTfs, with their superior physical properties, have been proposed as an alternative to non-conducting fatigue-resistant fibers used as surgical sutures (McCauley et al, 2019). In this approach, the combined electrical conduction capabilities of the CNTfs, along with their low impedance to ionic charge transfer, biocompatibility, and physiological stability make them ideal candidates that could potentially offer a restorative option while repairing myocardial lesions ( Figure 2).…”