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Page 4 of 15 Qiu et al. Vessel Plus 2018;2:12 I http://dx.doi.org/10.20517/2574-1209.2018.13

A 7
6 5
Stent diameter (mm) 4 3 PLLA

PLLA/PCL/TEC

2

1
0 1 2 3 4 5 6 7 8
Balloon pressure (bar)

B 14 C
P < 0.001 5 P = 0.001
12
4
10
Recoil (%) 8 6 Shortening (%) 3

4 2
2 1
0
PLLA PLLA/PCL/TEC PLLA PLLA/PCL/TEC

Figure 3. Stent diameter change against balloon pressure (A), elastic recoil (B) and stent shortening (C) [12]

a balloon pressure of ~2 bars. As a result, the pure PLLA stent achieved a smaller diameter (6.0 mm) than
that of PLLA/PCL/TEC stent (6.7 mm) at peak balloon pressure. Moreover, the pure PLLA stent exhibited
smaller elastic recoil (2.4%) and larger shortening (3.4%) compared to PLLA/PCL/TEC stent (8.8% and 2.3%,
respectively). These results suggested that material properties affected the mechanical behaviour of stents.

Schmidt et al. characterized the in vitro mechanical performance of bioresorbable scaffolds (i.e., Absorb
[13]
GT1, Elixir DESlove and Biotronik Dreams 2G) using the same method as described above. The crimped
stent had an outer diameter of 1.38 mm, 1.39 mm and 1.44 mm for Absorb GT1, Elixir DESlove and Dreams
2G, respectively. The Dreams 2G exhibited a pushability of 45.41% compared to 33.77% for Absorb GT1 and
36.27% for Elixir DESolve, but no significant difference was found for trackability of the three stents which
were 0.68 N, 0.75 N and 0.64 N for Dreams 2G, Absorb GT1 and Elixir DESlove stents, respectively. Moreover,
they examined and compared expansion behaviour of the three stents within a mock vessel and a rigid vessel
model. The Dreams 2G showed smaller recoil (5.6% and 5.0%) in both two cases without change over time,
while Absorb GT1 and Elixir DESolve stents showed time-dependent recoil. These results highlighted the
differences between metallic and polymeric BRSs due to different material properties and designs. Ormiston
et al. performed expansion and post-dilatation experiments for two commercially available bioresorbable
[14]
stents (Absorb and DESolve) and compared to typical metallic DES Xience Xpedition. They examined the
mechanical characteristics, such as crossing profile, recoil and radial strength, by imaging and intravascular
ultrasound techniques. The crossing profile had a diameter of 1.14 mm, 1.43 mm and 1.44 mm for Xpedition,
Absorb and DESolve, respectively. The radial strength of stent, measured in terms of pressure required to
reduce 25% of cross-sectional area, was found to be 1.6 atm for Xpedition, 1.4 atm for Absorb and 1.1 atm for
DESolve. All three stents showed elastic recoil after expansion with a slight change over time. Initially, all
three stents significantly recoiled by approximately 0.1 mm. Afterwards, Absorb and Xpedition continued
slight recoiling whereas the diameter of DESolve showed an increase (self-correction). Their results revealed