Coronary angioplasty is a technical marvel.  A thin tube is threaded from an artery in the groin to the heart.  Through this tube a tiny balloon is threaded into a narrowed coronary artery.  The balloon is inflated to open the artery, and then a stent (a metal mesh tube) is placed in the newly open artery to keep it open.  About a million coronary angioplasties are done in the United States annually. The procedure was initially developed with the hopes that opening narrow arteries would prevent...