Vascular stenting in normal and atherosclerotic rabbits. Studies of the intravascular endoprosthesis of titanium-nickel-alloy.

Abstract

Percutaneous transluminal balloon angioplasty would be more effective if the rate of recurrent stenosis were reduced. To evaluate the prevention of restenosis after percutaneous transluminal angioplasty, intravascular endoprosthetic stents of titanium-nickel-alloy were implanted transluminally in seven normal and 21 atherosclerotic rabbits. In normal rabbits, a 3.5-mm diameter stent was implanted in the aorta and a 2.5 -mm diameter stent in the right iliac artery, which were followed with serial angiograms from 6 weeks (n = 7) to 8 months (n = 4). There was a mean stenosis of 13.1% in the 2.5-mm and 13.6% in the 3.5-mm stent. There was no significant narrowing compared with the adjacent control segments of artery; histopathology showed a thin, fibrous neointima with smooth muscle cells. Each atherosclerotic rabbit was balloon dilated at two separate stenotic sites; each site was 2.0 cm in length. The aortic site (with 28.8±13.8% mean stenosis [±SD]) was dilated with a 3.5-mm balloon, and the iliac site (with 36.5 14.2% stenosis) was dilated with a 2.5-mm balloon. In each site, an intravascular stent of corresponding diameter and 7-mm length was implanted in one half of the dilated segment, assigned randomly, and the other half served as the angioplasty control. Angiographically observed restenosis rates and the corresponding histopathology were similar in the atherosclerotic segments that had angioplasty alone versus the atherosclerotic segments that had angioplasty plus stenting. The mean neointimal thickness in the aortas and iliac arteries, respectively, measured 247+181 pum (±SD) and 218±77 jm after 6 weeks (n=8) versus 321+168 and 308+189 ,um after 20 weeks (n=5, p=NS). At 20 weeks follow-up, there was 29.1+29.8% (median, 16.4%) stenosis in the aortic stent versus 38.9±24.1% (median, 34.0%) stenosis in the percutaneous transluminal angioplasty control segment of aorta (n =5, p =NS) and 81.4+25.5% stenosis in the iliac artery stent versus 89.3+15.3% stenosis in the PTA control segment of the right iliac artery (n=5, p=NS). Comparing stenotic arterial segments treated with angioplasty alone with angioplasty plus intravascular stenting in the atherosclerotic rabbits showed that there was no significant difference in either the histopathologic changes or the restenosis rates. (Circulation 1990;81:667-683) There is a need for an endovascular prosthetic stent for the treatment of symptomatic arterial dissection and acute occlusion resulting from percutaneous transluminal angioplasty (PTA).

Arterial Stenting and Overdilation: Does it Change Wall Mechanics in Small-Caliber Arteries?

“…24,25 Stent-induced flow disturbances have been reported in several in vitro models designed to simulate pulsatile flow through compliant arterial segments implanted with the Palmaz stent. 30,31 Studying the intimal response to stenting in animal models, Barth et al 32 and Sutton et al 33 found a larger thickness of neointima at the distal extremity of the stent than at the proximal or middle parts of the stent. Therefore, the preferentially distal location of intimal hyperplasia after stenting could be explained by a mechanical theory involving compliance mismatch.…”

Erste tierexperimentelle Ergebnisse eines von einer Polytetrafluoroethylenmembran umhüllten Koronarstents*

“…Diese Nachteile wurden dadurch umgangen, dass der Stent in die Membran eingehüllt und nicht die Membran von zwei Stents begrenzt wird. Somit veränderte die Architektur die mechanischen Eigenschaften des Stents nur gering, und die Platzierung in die im Mittel etwa 2,25 mm messenden Arteriae iliacae der Neuseelandkaninchen war weitgehend problemlos [19]. Die in mehreren klinischen Studien mit dem JoStent TM dokumentierten erfolgreichen Stentplatzierungen in 94 ± 98 % der Patienten bei absoluten Fallzahlen zwischen 33 und 77 und Gefäûdurchmessern von 3,5 mm [18, 20 ± 23] dürften auch mit vorliegendem PTFE-Stent erreichbar sein.…”

Indications and Results of Arterial Stents for Occlusive Disease

“…Robinson et al also reported that 4 weeks after bilateral percutaneous transluminal angioplasty (PTA) and unilateral stent deployment in atherosclerotic rabbits with induced iliac stenosis the stented iliac artery had a larger functional lumen and a decrease in the neointimal hyperplasia than at the contralateral nonstented site [14]. However, Sutton et al demonstrated no significant difference in the histopathologic changes or the restenosis rate between angioplasty alone and angioplasty plus stent at 20 weeks after stent deployment [15]. Thus it seems that longerterm data reveal no significant benefit from stent placement.…”