Page 10 - Journal of Structural Heart Disease Volume 3, Issue 6

Original Research Article
166
Table 1. Group demographics.
The purpose of the present study was to evaluate the impact of pre-stenting prior to intentional stent fracture in a piglet model.
Methods
Study Design
Experiments were performed using four 6-9-week- old piglets (7–11 kg), in which the aorta at various lev- els measured 5.7–10 mm. A total of 14 Cook Formula 418 stents (al1 2 mm length) were placed in the four piglets (three stents in two piglets and four stents in two piglets) at a diameter 1–3 mm larger than the vessel size to prevent stent migration. The pigs were allowed to grow for 5 months, during which time the aorta above and below the stent grew to 10.9–22 mm, with the area where the stent was placed being locked at its original size.
In two pigs (one with four stents and the other with three stents), the previously stented area was fractured using ultra-high-pressure Atlas balloons (Bard Peripheral Vascular, Temple, AZ, USA) with- out pre-stenting (single stent group). The Atlas bal- loons were over-sized for the region of the stent but matched the size of the adjacent vessel diameter.
In the other two pigs (one with four stents and the other with three stents), the previously stented area was pre-stented prior to stent fracture using Cordis Palmaz Genesis 1910 B peripheral stents (Cordis, Hi- aleah, FL, USA; pre-stent group). The Genesis stents were mounted on Cordis Power ex (Cordis, Hialeah, FL, USA) or NuMED BIB (NuMed Inc., Hopkinton, NY, USA) balloon catheters. The Genesis stents were se- lected for the second set of stents because they are commonly used in the pediatric population and can be ultimately dilated to reach adult vessel size. Bal- loon size was selected to match the adjacent vessel diameter. Balloon catheters were in ated to their re- spective recommended maximum pressure to place the Genesis stents inside the smaller Cook Formula stents. High-pressure Atlas balloons were then used to dilate the secondarily placed Genesis stents with simultaneous intentional fracture of the smaller Cook Formula stents.
Two pigs (short-term group; one each from the single stent and pre-stent groups, total of seven stents) were euthanized immediately and the tissue
Volume 3, Issue 6:165-175
Re-stent group
Single stent group
p-value
n=7 n=7
Piglet weight (kg) Original Stent
Type
Stent Size (mm)*
4 5,6 7,8
Fracture diameter (mm)
12 16 20
Fracture atm (mean)
* All Formula 418 stents were 12mm in length
** Higher atm for the single stent group can be explained by the fact that the stents were thinner and harder to visualize in the older pig, so more atmo- spheres were used to insure that they were broken.
and the EV3 stent having the lowest score [6].
Five intentional longitudinal stent fractures were reported in humans using high-pressure balloons without immediate adverse events [7]. In situ spon- taneous stent fracture in humans is not uncommon and has been reported in up to 21% patients, with resultant obstruction in 80% (of which 39% were con- sidered severe). Some fractures can cause stent col- lapse, hemodynamic compromise, and embolization of stent fragments, requiring additional intervention in 75% of cases [8, 9]. In a large report of the spon- taneous fracture of 3,650 stents, there was a 42% incidence of in-stent restenosis and 4.6% incidence of thrombosis [10]. Furthermore, in a study demon- strating the feasibility of intentional stent fracture in humans, there was a signi cant incidence of compli- cations (15%), including embolization of stent frag- ments, unstable stent fracture, vascular tear, non-ob- structive intimal tear, and aorto-pulmonary window. All complications except embolization were prevent-
ed by pre-stenting [11].
Journal of Structural Heart Disease, December 2017
6.6
Formula 418
n=3 n=4 n=0
n=3 n=4 n=0
14.7 ±4.9
8.1 0.0342
Formula 418
n=1 n=4 n=2
n=1 n=4 n=2
18.4 ±4.8 **
0.1766