Failure to post-dilate BeSmooth peripheral stents to adult vessel size diameters during bench-side tests

Introduction

Low-profile stent implantation remains a rescue treatment for aortic coarctation and branch pulmonary arteries stenosis in small children. Stent re-expansion to cope with vascular growth remains problematic.

Objective

To evaluate ex-vivo feasibility and mechanical behavior of over-dilating BeSmooth peripheral stents (Bentley InnoMed, Germany).

Methods

Three BeSmooth stents in diameters of 7, 8, and 10 mm were dilated to nominal pressure and then 13atm. Test-1 (sequential up-sizing post-dilation without re-stenting): BeSmooth Ø7 × 23 mm was post-dilated using 12, 14, and 16 mm high-pressure balloons. Test-2 (post-dilation until plateau/breakpoint then re-stenting): BeSmooth Ø10 × 57 mm was post-dilated with 14 mm balloon until plateau/breakpoint and then with 48 mm bare-metal Optimus-XXL stent hand-mounted on 14 mm balloon. Test-3 (straightforward re-stenting): BeSmooth Ø8 × 57 mm was directly post-dilated with 48 mm bare-metal Optimus-XXL stent hand-mounted on 16 mm balloon. The stents’ diameter and length were measured. Balloon rupture and stent fracture patterns were closely evaluated.

Results/Expected results

Test-1: BeSmooth Ø7 × 23 mm was post-dilated to 10 mm diameter with a little shortening. Up-sizing the stent to 11 mm with the Ø14 mm balloon led to the stent shrinking to 3.2 mm. At 20atm pressure, BeSmooth Ø7 × 23 mm shortened to 2 mm forming a 12 mm diameter solid ring circle, and the 16 mm woven balloon ruptured radially. Test-2: The BeSmooth Ø10 × 23 mm reached a plateau diameter of 13 mm without shortening and the balloon did not rupture. Stent-in-stent re-expansion showed that at 10atm pressure, BeSmooth Ø10 × 57 mm fractured longitudinally in various dispatched breaking points at a diameter of 13 mm without shortening and ruptured the balloon with multiple pinholes. Test-3: At 10atm pressure, BeSmooth Ø8 × 57 mm fractured centrally at three different points at a diameter of 11.5 mm without shortening and the balloon broke radially in half.

Conclusion/Perspectives

In our benchmark tests, extreme shortening, severe balloon rupture, or unpredictable stent fracture patterns at small balloon diameters limits the safe post-dilation of BeSmooth stents beyond 13 mm. BeSmooth stents are not ideal candidates for off-label stent interventions in smaller patients.