A new and emerging understanding of how heart attacks occur indicates that increasingly popular aggressive treatments may be doing little or nothing to prevent them. The artery-opening methods, like bypass surgery and stents, the widely used wire cages that hold plaque against an artery wall, can alleviate crushing chest pain. Stents can also rescue someone in the midst of a heart attack by destroying an obstruction and holding the closed artery open. But the new model of heart disease shows that the vast majority of heart attacks do not originate with obstructions that narrow arteries. Instead, recent and continuing studies...