Gross specimen evaluation
Gross examination of the regions of injection was undertaken by first dissecting out the entire transmural region where ablation was performed. We then did two orthogonal incisions through the center of the lesion region to be able to evaluate the myocardium throughout the ablated region. Presence of the conductive hydrogel was based on the gross appearance throughout the region given that the black appearance of the hydrogel is otherwise obvious against the surrounding myocardial tissue. No specific quantification was done of the amount of hydrogel retained within the volume of ablated tissue.