What is it about?

The presented experimental in vitro approach was designed to assess the expansion behavior of stent systems in a resistant focal stenosis model with respect to a potential dog-boning effect. Five different stent systems (nominal diameter 3.0 mm) were investigated. The focal stenosis was simulated by a stainless steel tube (ID ≤ 1.20 mm). Stent expansion was performed using a proprietary test device consisting of a test chamber with 37 °C water, 2-axis laser scanner and a pressure controller. All stents could be properly expanded up to recommended maximum pressure (RBP). At nominal pressure (NP) maximum diameters ranged from 2.923 to 3.560 mm while at RBP the maximum diameters were 3.391 to 3.984 mm. Only minimal flaring of stent struts from the expanded balloon was observed. None of the stent systems failed under the extremely high stress at the edges of the focal stenosis.

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Why is it important?

Summarizing the results it can be stated that a particular risk by flaring stent struts was not observed even in the case of stent expansion in a resistant focal stenosis. However, the data show a potential risk for vessel injury if the maximum outer diameter at expansion is clearly above the expected diameter. Consequently, in particular at maximum balloon pressure care should be taken by the interventionists to achieve optimal stent sizing under such extreme conditions.

Perspectives

Mechanical in vitro-testing is a powerful tool to investigate and understand the behavior of vascular implants even in critical situations. In our case, the importance of best diameter matching of stents is shown but the simulation of resistant focal stenoses did not reveal specific challenges with respect to this challenge. I would highly appreciate to share experiences and technical results with experienced medical researchers.

Dr. Wolfram Schmidt
University Medicine Rostock

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This page is a summary of: Expansion characteristics of coronary stents in focal stenoses, Current Directions in Biomedical Engineering, January 2017, De Gruyter,
DOI: 10.1515/cdbme-2017-0029.
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