I recently had a stent implanted to keep an artery open, but I’ve heard that they sometimes fail. How common is that? —L.B., Ithaca, N.Y.

It may depend on the type of stent. As many as 40 percent of people who receive older "bare metal" stents experience reclogging of the artery, usually within six months of the surgery. The failure rate for the newer drug-coated stents in the first six months appears to be much lower, about 5 percent, though some evidence suggests that they may fail more frequently than older versions after a year. Depending on the amount of blockage, signs of a failed stent can range from none at all to typical heart-attack symptoms such as chest pain during exercise. So it’s important to have regular checkups with your cardiologist after receiving a stent.