Neointimal hyperplasia and late pathologic remodeling in a porcine coronary stent model

Although coronary stenting has been demonstrated to significantly reduce restenosis compared to conventional angioplasty, occurrence of in-stent stenosis still remains one of the major limitations. This study investigates the influence of stent strut diameter on injury, inflammatory response, thrombosis and neointimal hyperplasia in a porcine coronary artery.

Coil stents made of either a 0.12 mm, 0.15 mm or 0.18 mm wire were randomly implanted in the right coronary arteries of 30 pigs. Quantitative coronary angiography analysis was performed before, immediately after, and 6 weeks following the stenting procedure. At 6 weeks, histopathology for evaluation of injury, thrombosis and inflammation, as well as morphometry for calculation of the neointimal hyperplasia and internal elastic lamina area were performed.

Quantitative coronary analysis showed similar quantitative data before and after stent placement in the three groups. At 6 weeks, however, a significantly bigger MLD was found in the 0.18 mm group. Morphometric analysis at 6 weeks confirmed these results, showing a significantly bigger lumen area in both the 0.18 mm (1.71 +/- 0.66 mm2) and 0.15 mm (1.36 +/- 0.53 mm2) groups compared to the 0.12 mm group (0.71 +/- 0.38 mm2). The calculated neointimal hyperplasia was similar in the three groups (0.12 mm: 1.93 +/- 0.51 mm2; 0.15 mm: 1.68 +/- 0.63 mm2; and 0.18 mm: 2.16 +/- 1.48 mm2). The internal elastic membrane area, however, was significantly bigger in the 0.18 mm (3.87 +/- 1.39 mm2) compared to the 0.12 group (2.65 +/- 0.53 mm2).

These results suggest that pathologic remodeling can also play an important role in late lumen loss after stent implantation.