Comparison of the thrombogenicity of stainless steel and tantalum coronary stents.

This study was designed to compare the thrombogenicity of stainless steel and tantalum coronary stents of the same design. Stainless steel and tantalum coronary stents are being evaluated for their utility in treating acute closure and restenosis. A major disadvantage of stainless steel stents is radiolucency. To determine whether radioopaque tantalum stents may be safely substituted for stainless steel stents, we compared the relative thrombogenicity of these materials in stents of identical design. Total platelet and fibrin deposition on the stents were determined from measurements of indium 111-labeled platelet and iodine 125-labeled fibrinogen accumulation after deployment into exteriorized chronic arteriovenous shunts in seven untreated baboons. In another series of experiments, 111In-platelet deposition was compared 2 hours after stent implantation in coronary arteries of pigs. In baboons, platelet thrombus formation on stainless steel and tantalum stents was equivalent and plateaued at approximately 2.5 x 10(9) platelets after 1 hour (p > 0.05). Fibrin deposition averaged approximately 1 mg/stent and did not differ between the stainless steel and tantalum stents (p > 0.05). In the porcine coronary model there was no significant difference in 111In-labeled platelet deposition between the stainless steel and tantalum stents (p > 0.05). This result was confirmed by scanning electron microscopic analysis of the coronary stents. Based on these two models, we conclude that there is no significant difference in the thrombogenicity of stainless steel and tantalum wire coil stents.