People who suffer heart attacks are at increased risk of having a second and potentially fatal occurrence because of the damage the heart attack does to cardiac muscle tissue. Now scientists at the University of California San Diego have developed a new biomaterial - an injectable hydrogel - that can repair the damage from heart attacks, and help promote the growth of new heart tissue.  Millions of people around the world suffer heart attacks every year and survive. These traumatic events occur when blood supply to the heart muscles is somehow blocked, robbing them of oxygen and causing them...