The F-D-A gave its approval Thursday to a new type of stent to block open arteries and the first one in Iowa was surgically implanted in a patient this morning. Stents were first introduced in 1995. They’re very small stainless steel tubes put inside the arteries when there’s a blockage discovered that could cause a stroke or heart attack. The problem is, stents can allow tissue to build up around them in some patients, causing them to need another surgery. Davenport cardiologist Dr. Ed Coyne says the new stents have a special coating — a drug — which helps prevent tissue regrowth.The drug lasts about a month, which Dr. Coyne says is the length of time that tissue regrowth within the artery is usually a problem. He says it’s hoped the new stents will cut the risk of a needed second surgery from 20-percent down to five percent. Coyne inserted the new type of stent in a patient this morning at Genesis Medical Center in Davenport, where about 21-hundred heart surgeries are performed every year.