CYPHER coronary stents and risk of thrombosis

Reason for posting: The use of coronary stents has improved the results of percutaneous coronary revascularization procedures. Along with newer antithrombotic therapy using glycoprotein IIb/IIIa platelet inhibitors, stents are used frequently in the management of acute coronary syndromes.1-3 However, a persistent problem with stents is the subsequent development of in-stent stenosis. Data from the British Columbia Cardiac Registries during the mid-1990s show that restenosis occurs in about 15% of patients with stents.1 To prevent this, stents have now been developed that are coated with drugs believed to be helpful in maintaining stent patency. Initial clinical trials of these drug-eluting stents have been completed and other trials are underway. In its letter to physicians, the manufacturer notes that some cardiologists may be inappropriately inserting the stents, mainly by overexpanding narrower stents so that they will fit in arteries with larger diameters. The manufacturer reports that because of high demand for the stent it focused its production on the smaller stents but is now producing a larger stent. The manufacturer also notes that some in-vitro laboratory experiments show that sirolimus potentiates the effect of some platelet agonists and thus may promote thrombus formation. Furthermore, it should be noted that in 1 major study that demonstrated the benefits of the CYPHER stent7 the device was investigated in a limited clinical application. Patients were eligible if they had disease of a native coronary artery (i.e., those with diseased grafts were excluded) in the setting of stable or unstable angina, or silent ischemia. Importantly, acute myocardial infarction was one of numerous exclusion criteria.