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Drug Information Rounds

Approximately 400 000 Americans undergo nonsurgical coronary artery interventional procedures each year. The use of coronary artery stents is increasing rapidly and, in some laboratories, more than 50% of the patients undergoing angioplasty have coronary artery stents implanted.' Coronary artery stents fall into two broad categories, balloon expandable and self-expanding, based on their method of delivery and expansion within the coronary artery. Two balloon expandable stents (Gianturco-Roubin and Palmaz-Schatz) are approved for use in the US by the Food and Drug Administration (FDA) and numerous others are under investigation in clinical trials. Balloon expandable stents are available in two designs, metallic coil and slotted tube, which are delivered to the coronary artery mounted on an angioplasty balloon with (Palmaz-Schatz stent) or without (Gianturco-Roubin stent) a protective sheath.' Based on the thrombogenic nature of a stent, potential endothelial damage induced by the stent, and previous experiences with angioplasty, investigators recognized the potential for thrombus formation and/or restenosis of the coronary artery at the site of stent implantation. Antiplatelet agents were originally proposed as the sole medications to prevent subacute thrombosis after stent placement, but their use was associated with poor outcomes.' Schatz et al.' conducted a multicenter study in which stents were successfully implanted in 213 patients after elective percutaneous transluminal coronary angioplasty (PTCA). Aspirin 325 mg/d po and dipyridamole 75 mg po three times daily were started 2~8 hours before stent placement and continued for 3 months following stent placement. Because of an 18% subacute thrombotic closure rate within 2-11 days after stent placement, only the first 39 patients received this regimen. The study protocol was amended to include warfarin, and the subacute thrombotic closure rate decreased to 0.6%. The investigators concluded that a short course of anticoagulation, in addition to anti platelet agents, should be used in all patients undergoing stent implantation. However, they also acknowledged that the high subacute thrombotic closure rate observed in patients not receiving anticoagulation thera-