Stent strut thickness and restenosis.

To the Editor: Kastrati et al recently reported1 significantly less restenosis with lesions randomized to deployment of one stent design (ACS RX Multi-Link, [ML]) than with a related design (Multi-Link RX Duet, [DT]) from the same manufacturer (Guidant). They attributed the difference in restenosis to the difference in strut thickness. Although the two stent designs do differ significantly in strut thickness, there are other differences in design and mechanical properties that might impact on restenosis. The DT has greater radial strength: when tested in vitro in a pressure chamber, the DTs collapsed at a higher pressure (1.81 0.01 atm) than the MLs (0.77 0.03 atm, P 0. 05) (unpublished observations). Some experimental data suggest that greater stent hoop strength may cause increased neoimtimal proliferation.2 The extent of metal coverage of vessel wall is greater for the ML (22.3%) than for the DT (16.5%). The gap size or uncovered area between the stent struts also differs. The ML has gaps of one size (area 3.3 0.1 mm) whereas the DT has gaps of two sizes, one similar in size (3.3 0.4 mm) to the ML and one bigger (4.9 0.4 mm, P 0.01) (unpublished observations). The larger-sized gaps may allow greater tissue prolapse and increased restenosis analogous to the original Palmaz-Schatz stent where restenosis occurred mostly at the articulation site.3 On the other hand, we found no differences between the ML and the DT for expanded stent flexibility4 or for acute recoil, so these do not explain the difference in restenosis rates. Besides strut thickness, there are other differences in mechanical and physical properties between the expanded ML and DT stents that are equally plausible explanations for the differences in restenosis rates between the two designs. These differences may have implications for the design of stents with low restenosis rates.