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Determination of the minimum inflation time necessary for total stent expansion and apposition: an in vitro study.

OBJECTIVE
Determine minimum inflation time necessary for total stent expansion and apposition.


BACKGROUND
Complete stent expansion is needed to adequately support the increase in artery lumen and to accommodate neointimal growth.


METHODS
Experimental in vitro study. Twenty-five silicon carbide-coated stainless steel stents (3.5 x 20 mm) were released (14 atm) in plastic vials with a 3.5 mm internal diameter. Five groups, with 5 stents each, were set. Stents from Group A were released with 5 seconds of inflation; stents from Group B, with 15 seconds; stents from Group C, with 30 seconds; stents from Group D, with 60 seconds; and stents from Group E, with 90 seconds. Immediately after release, an intrastent ultrasound evaluation was performed for analysis of intrastent volume and apposition. Data were analyzed by Tukey's test and Fisher's exact test.


RESULTS
Group A, mean intrastent volume (MIV) was 161.1 +/- 7.5 mm3, 60% complete apposition; Group B, MIV was 180.2 +/- 6.0 mm3, and 80% complete apposition; Group C, MIV was 183.0 +/- 1.1 mm3, 100% complete apposition; Group D, MIV was 183.2 +/- 1.8 mm3 and 100% complete apposition; and Group E, MIV was 183.5 +/- 0.7 mm3, and 100% complete apposition. MIV was significantly different only in Group A, as compared to all other groups, and only stents in Groups A and B were nonapposed. The exponential curve of the relationship between inflation time/volume obtained showed maximum efficiency starting at 30 seconds.


CONCLUSION
The experimental models used in this study showed that 15 seconds may be adequate, but 30 seconds and more appear very adequate for optimum stent deployment, expansion and apposition.