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.

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

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

Test-1: BeSmooth Ø7×23mm was post-dilated to 10mm diameter with a little shortening. Up-sizing the stent to 11mm with the Ø14mm balloon led to the stent shrinking to 3.2mm. At 20atm pressure, BeSmooth Ø7×23mm shortened to 2mm forming a 12mm diameter solid ring circle, and the 16mm woven balloon ruptured radially. Test-2: The BeSmooth Ø10×23mm reached a plateau diameter of 13mm without shortening and the balloon did not rupture. Stent-in-stent re-expansion showed that at 10atm pressure, BeSmooth Ø10×57mm fractured longitudinally in various dispatched breaking points at a diameter of 13mm without shortening and ruptured the balloon with multiple pinholes. Test-3: At 10atm pressure, BeSmooth Ø8×57mm fractured centrally at three different points at a diameter of 11.5mm without shortening and the balloon broke radially in half.

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 13mm. BeSmooth stents are not ideal candidates for off-label stent interventions in smaller patients.