A comparison of four stent designs on arterial injury, cellular proliferation, neointima formation, and arterial dimensions in an experimental porcine model

The stent-artery interactions of different stent designs have implications for their clinical effects, We studied four different stent designs to comp are their effects on arterial injury, cellular proliferation, neointima for mation, and arterial dimensions. Eighteen nonatherosclerotic miniswine unde rwent random placement of 52 coronary stents (3.0 mm), including self-expan ding nitinol stents inc postdilation; Radius, n = 13) and balloon-expandabl e stents (8 atm x 45 sec; Palmaz-Schatz, n = 13; EX, n = 12; and Multilink, n = 14). Cellular proliferation was determined by S-phase labeling with Br dU at 7, 14, and 28 days. Proliferation, injury scores, and arterial morpho metry were blindly evaluated, All four stent designs had similar injury sco res, cellular proliferation indexes (neointimal and medial), and adventitia l areas. Nitinol stents resulted in a twofold increase in neointimal area a nd thickness in 28-day vessels (P = 0.002), However, lumen area was similar for all stent designs because of an offsetting expansion in vessel area in nitinol stents (20% greater than balloon-expandable stents) occurring betw een 7 and 14 days after stent deployment (P = 0.03). Reduced neointimal cel l density in nitinol stents (20% less than balloon-expandable stents, P = 0 .012) suggests that extracellular matrix expansion accounts for the larger neointima in nitinol stents. Self-expansion of nitinol stents within normal porcine arteries results in a similar degree of arterial injury compared t o balloon-expandable stent designs. Progressive enlargement of nitinol sten ts between 7 and 14 days after deployment is associated with the developmen t of a larger, matrix-rich neointima, with a preserved lumen area. Publishe d 2001 Wiley-Liss. Inc.