Morphological Characteristics of Intimal Hyperplasia in Stented Coronary Arteries Assessed with Intravascular Ultrasound

Background

Intravascular ultrasound(IVUS) provides high resolution cross-sectional images of the vessels and permits the quantiative and qualitative assessment of coronary artery disease. Stent is a figid endovascular lattice that effectively prevents elastic recoil at treated sites, but in-stent restenois is a major limitation. The purpose of thecurrent study is to assess the contribution of neointimal hyperplasia for in-stent restenosis and the distribution and morphological characteristics of neointimal hyperplasia in deployed stents.

Methods

Thirty patients(male 25 & female 5;31 leions) deployed with intracoronary stents underwent intravascular ultrasound imaging at follow-up at least 4 months after stenting ([mean±SD] 8.3±2.9 months).

Results

1) In-stent restenosis occurred in 15 lesions out of 31 lesions at follow-up coronary angiography. There was no difference in clinical characteristics between the restenotic and the non-restenotic groups.

2) There was no difference in angiographic profiles between two groups. Deployed stents were as follows ; 16 Palmaz-Schatz(P-S) stents, 12 Gianturco-Roubin(G-R) stents, 2 Cordis stents, and 1 Microstent II. Average diameter of stents in the restenotic and the non-restenotic groups were 3.07±0.26mm and 3.16±0.30mm, respectively(p=0.38).

3) There was no difference of stent cross-sectional areas(CSA) between the non-restenotic and the restenotic groups(p=0.476), but luminal CSA of the restenotic group was significantly smaller than that of the non-restenotic group(p=0.006).

4) In the restenotic group, there were no differences of the maximal and the minimal diameters of stents, and the mean CSAs of stents among proximal, mid, and distal segments. But the mean CSA of neointimal hyperplasia at the mid segment was larger than that at the distal segment(p<0.05). There was a tendency that the mean CSA of neointimal hyperplasia at the mid segment was larger than that at the proximal segment(p=0.187). These findings were the same in the non-restenotic group.

5) In the restenotic group deployed with P-S stents, there were no differences of the maximal and the minimal diameters of stents, and the mean cross-sectional areas(CSA) of stents between each segment. But, the mean CSA of neointimal hyperplasia at the mid segment was larger than that at the distal segment(p<0.05) and there was a tendency that the mean CSA of neointimal hyperplasia at the mid segment was larger than that at the proximal segment(p=0.354).

6) In the morphology of neointimal hyperplasia of the restenotic group, eccentric form(77%) was more common than concentric form(22%). Neointimal hyperplasia occurred in focal or diffuse patterns(7 versus 8 cases).

Conclusions

In-stent restenosis resulted from neointimal hyperplasia which almost mainly occurred eccentrically at the mid segment of stents and in focal or diffuse patterns. Intravascular ultrasound imaging was a useful method for recognition of distribution and morphological characteristics of neointimal hyperplasia at follow-up of deployed stents.