Coronary Fix: Coated inserts keep vessels unclogged

Doctors started opening blocked coronary arteries with balloon-tipped catheters in the 1970s, but repeat narrowing of those vessels sent many patients back to the hospital. In the 1980s, scientists devised mesh cylinders called stents that prop open the arteries after the balloon is withdrawn. Even with stents, however, one-fourth of reopened vessels become obstructed again within 6 months.