Preservation of conductive propagation after surgical repair of cardiac defects with a bio-engineered conductive patch

Background: Both stable and biodegradable biomaterials have been used to surgically repair congenital cardiac defects. However, neither type of biomaterial can conduct electrical activity. We evaluated the conductivity and efficacy of a newly synthesized conductive polypyrrole-chitosan (Ppy+Chi) gelfoam patch to support cardiomyocyte (CM) viability and function in vitro and to surgically repair a cardiac defect in vivo.

Methods: Ppy+Chi was incorporated into gelfoam (Gel) to form a 3-dimensional conductive patch. In vitro, patch characteristics were evaluated and biocompatibility and bioconductivity were investigated by culturing neonatal rat CMs on the patches. In vivo, a full-thickness right ventricular outflow tract defect was created in rats and the patches were implanted. Four weeks after patch repair, cardiac electrical activation and conduction velocity were evaluated using an optical mapping system.

Results: In vitro, the Ppy+Chi+Gel patch had a higher mean breaking stress than the Gel or Chi+Gel patches, and the highest conductivity. None of the patches altered cell growth. The Ca²⁺ transient velocity of CMs cultured on the Ppy+Chi+Gel patch was 2.5-fold higher than that of CMs cultured on the Gel or Chi+Gel patches. In vivo, optical mapping at 4 weeks post-implantation demonstrated that Ppy+Chi+Gel patch-implanted hearts had faster conduction velocities, as measured on the epicardial surface. Continuous electrocardiographic telemetry did not reveal any pathologic arrhythmias after patch implantation. Ex-vivo patch conductivity testing also revealed that the Ppy+Chi+Gel patch was more conductive than the Gel and Chi+Gel patches.

Conclusions: The Ppy+Chi+Gel patch was biocompatible, safe and conductive, making it an attractive candidate for a new biomaterial platform for cardiac surgical repair to preserve synchronous ventricular contraction.