Re-entrant arrhythmias are the leading causes of sudden cardiac death. Access to the coronary veins that cross the scarred region of the heart where reentrant circuits originate could provide improved pacing to prevent ventricular arrhythmias and circumvent the need for painful defibrillation. However, there are no pacing leads small enough to navigate these smaller tributaries and epicardial approaches have limited efficacy due to the greater mass and thickness of ventricular tissue. We have developed an injectable hydrogel electrode that can fill coronary veins to convert them into flexible electrodes that directly pace the inaccessible mid-myocardium. In our two-component system, hydrogel precursor solutions can be injected through a dual lumen catheter in a minimally invasive deployment strategy to provide direct access to the diseased regions with relative precision and ease. Mixing of the two solutions upon injection into the vein activates redox-initiated crosslinking of the gel for rapid in situ cure without an external stimulus. An ex vivo porcine model was used to identify the requisite viscosity and cure rate for gel retention and homogeneity. Ionic species added to the hydrogel precursor solutions conferred conductivity above target myocardium values that was retained after implantation. Successful in vivo deployment demonstrated that the hydrogel electrode filled the anterior interventricular vein with extension into small venous tributaries, far deeper into the mid myocardium than currently available lead placement. In addition to successful capture and pacing of the porcine heart, analysis of surface ECG tracings revealed a novel pacing paradigm not observed in traditional single-point pacing: capture of both myocardium and the Purkinje system. This combination is a pacing modality that most closely resembles native, healthy sinus conduction. Notably, this is the first report of an injectable electrode used to successfully pace the mid-myocardium and mimic physiologic conduction.

Keynote: Towards prevention of arrhythmias:  Injectable hydrogel electrodes enable direct capture of inaccessible cardiac tissues

ACS Spring 2022

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