Electromechanical characterization of a tissue-engineered myocardial patch derived from extracellular matrix

Objective: Extracellular matrix scaffolds have been successfully used for myocardial wall repair. However, regional functional evaluation (ie, contractility, electrical conductivity) of the extracellular matrix scaffold during the course of remodeling has been limited. In the present study, we evaluated the remodeled scaffold for evidence of electrical activation. Methods: The extracellular matrix patch was implanted into the porcine right ventricular wall (n=5) to repair an experimentally produced defect. Electromechanical mapping was performed with the NOGA system (Biosense Webster Inc, Diamond Bar, Calif) 60 days after implantation. Linear local shortening was recorded to assess regional contractility. After sacrifice, detailed histologic examinations were performed. Results: Histologic examinations showed repopulation of the scaffold with cells, including a monolayer of factor VIII-positive cells in the endocardial surface and multilayered alpha-smooth muscle actin-positive cells beneath the monolayer cells. The alpha- smooth muscle actin - positive cells tended to be present at the endocardial aspect of the remodeled scaffold and at the border between the remodeled scaffold and the normal myocardium. Electromechanical mapping demonstrated that the patch had low-level electrical activity (0.56 +/- 0.37 mV; P <.0001) in most areas and moderate activity (2.20 +/- 0.70 mV; P <.0001) in the margin between the patch and the normal myocardium (7.58 +/- 2.23 mV). Conclusions: The extracellular matrix scaffolds were repopulated by alpha- smooth muscle actin - positive cells 60 days after implantation into the porcine heart. The presence of the cells corresponded to areas of the remodeling scaffold that showed early signs of electrical conductivity.