Stent Deployment: Keep the Pressure On

Adequate stent deployment is one of the most important technical factors during percutaneous coronary intervention. Inadequate stent expansion or apposition allows a nidus for stent thrombosis and in-stent restenosis. The factors affecting this process should be completely elucidated. Deployment of a stent at higher pressures and under intravascular ultrasound (IVUS) guidance has been shown to facilitate optimal stent expansion and maximizes acute luminal gain. However, data regarding optimal inflation time during stent deployment are lacking.

In this issue of the journal, Trindade et al1 have taken the initiative to study the role of inflation time during stent deployment. In their experimental in vitro study, 25 silicon carbide-coated stainless steel stents, each measuring 3.5 mm x 20 mm, with a nominal pressure of 10 atm were deployed at 14 atm in 25 plastic vials, each measuring 3.5 mm x 50 mm. Five groups of 5 stents in each group were randomly set, and stents in the 5 groups were released at 14 atm for 5 seconds, 15 seconds, 30 seconds, 60 seconds and 90 seconds, respectively. An intrastent ultrasound evaluation was performed immediately after stent deployment to assess the degree of stent apposition and also to measure the intrastent volume. Stents released at 5 seconds had 60% complete apposition, those at 15 seconds had 80% apposition, and groups deployed over 15 seconds had near 100% apposition. Intrastent volume was also inadequate and significantly lower in the group deployed over 5 seconds compared to the rest of the groups. Inflation time correlated directly with intrastent volume, with maximum efficiency starting at 30 seconds. The authors concluded that stents deployed at 15 seconds or longer offered optimal stent deployment.

The authors must be commended for the systematic approach in their methodology of the study design, and deserve credit for addressing this important yet not-so-well studied principle of stent deployment. Limitations of the study include its in vitro design, which calls for validation with in vivo animal models and potentially among human subjects. Furthermore, different stent types — both drug- eluting and bare-metal — as well as different vessel characteristics (tortuosity, calcification, thrombus, etc.) all require study.

In summary, this study further strengthens the argument in favor of deploying a stent at nominal or higher pressures over a period of ≥ 15 seconds to achieve an adequate deployment.