EFFECTS OF DESIGN GEOMETRY OF INTRAVASCULAR ENDOPROTHESES ON STENOSIS RATE IN NORMAL RABBITS

To investigate the effects of gaps between the individual wire coils of a shape memory Nitinol alloy intravascular endoprosthesis, 20 stents with and without gaps were implanted transluminally into the infrarenal abdominal aortas of 10 normal rabbits after balloon angioplasty. Digital subtraction angiography (DSA) was done at 4, 12, 16, 20, and 24 weeks after stent implantation to examine the stenosis rate and major side branch patency. Stenosis rate within stents with gaps were significantly lower than those without gaps: 8.1 +/- 5.0% versus 15.0 +/- 6.8% at 12 weeks, 13.6 +/- 6.0% versus 26.0 +/- 9.4% at 24 weeks by DSA, p > 0.005 and p < 0.01 respectively. The maximum and mean neointimal thickness measured histologically at the time of animal death correlated significantly to the narrowest diameter obtained from the DSA studies, (r = 0.84 and r = 0.79, respectively, p < 0.01). Greater hyperplasia of the neointima was evident in the stented arterial segments with stents without gaps compared with those with gaps (83 +/- 22 versus 187 +/- 46-mu-m mean thickness, p < 0.001). The patency rate of the side branches in the stented arterial segment was significantly (p < 0.05) higher in stents having gaps. These results suggest that the placement of gaps between wire pitches reduced the neointimal thickness within stents and prevented the obstruction of arterial side branches.