When it comes to matters of the heart, big is usually better. But big and floppy is another story. After a heart attack or other assault that weakens the heart's muscles, the organ begins to enlarge. The stress can kill so many cells that the heart begins to look like a "big floppy bag," says Dr. Hani Sabbah, the inventor of a mesh-like jacket that protects against the stretching that leads to heart failure. It's currently in clinical trials.