Time is of the essence when treating a patient undergoing a heart attack. Cardiac surgeons attempt to quickly stabilize the heart by applying reperfusion, a technique that restores oxygen to the heart by opening up blocked vessels with balloons and stents. While reperfusion can restore cardiac function, such sudden infusions of oxygen can also further injure severely depleted regions of the heart.“It’s a double-edged sword,” says Anthony McDougal, a graduate student in MIT’s Department of Mechanical Engineering. “The rapid return of oxygen is necessary for the heart to survive, but it could also overwhelm the heart.”