Narrator: This is Science Today. A heart attack has two phases of injury. The first is when a blood clot forms in a coronary artery, blocking blood flow. But there's a second, less well appreciated phase called reperfusion injury. Dr. Marcus Horwitz, of UCLA, says reperfusion injury actually causes about sixty percent of the total damage to the heart after an attack.

Horwitz: It would occur with any heart attack victim or stroke. Wherever you have a situation where blood supply is cut off from an organ, such as the heart and then that blood supply is restored, reperfusion injury will take place.

Narrator: In this phase, white blood cells flow to the oxygen deprived heart tissue, releasing toxic molecules which damage the heart. This can't happen without iron, so Horwitz is working with an iron-binding tuberculosis molecule to prevent this toxic reaction.

Horwitz: The molecule that we have prevents iron from participating in that chemical reaction so that the toxic oxygen molecule is now produced and reperfusion injury does not take place.

Narrator: For Science Today, I'm Larissa Branin.