Methods and systems are disclosed for treating injury to cardiac tissue by delivering a composition which provides structural support to the cardiac tissue. The composition helps to prevent chamber remodeling by providing structural reinforcement of the tissue or structural reinforcement of the tissue combined with biological therapy. The structurally reinforcing composition can thicken the wall of a heart, or act to prevent further thinning and thereby provide resistance against further remodeling. A number of compositions are disclosed, including multi-component substances such as autologous platelet gel, and other substances. The compositions disclosed can contain additives to augment/enhance the desired effects of the injection.