Drug and medical device company Abbott Laboratories said Tuesday that the U.S. Food and Drug Administration has approved its stent system for treating coronary artery disease in small blood vessels.

Stents are mesh-metal tubes used to prop open arteries after they have been cleared of potentially deadly fat deposits. But the process becomes more difficult when trying to treat smaller blood vessels.

Abbott's Xience nano can be placed in blood vessels as small as 2.25 millimeters in diameter. It has thin struts and a drug coating used to prevent scar tissue from growing around the stent and reclogging the patient's artery.

Clinical trials of Xience nano showed very low levels of blood vessel re-narrowing.

North Chicago-based Abbott already leads the U.S. market for stents with its Xience V drug-coated stent.

Similar products are marketed by Johnson & Johnson, Medtronic Inc. and Boston Scientific.

Shares in Abbott Laboratories added 2 cents to $53.35 in aftermarket trading after adding 8 cents to $53.33 during the regular session.