Arterial remodeling and hemodynamics in carotid stents: a prospective duplex ultrasound study over 2 years.

OBJECTIVE

This study was undertaken to study negative and positive arterial remodeling processes within self-expanding carotid stents, their interaction, and the resulting changes in hemodynamics over 2 years, with duplex ultrasound scanning.

SUBJECTS AND METHODS

One hundred twelve consecutive patients with 121 successfully stented carotid arteries were examined with color-coded duplex ultrasound scanning the day after the stent procedure and at 3, 6, 12, and 24 months of follow-up. The stent diameters at the proximal, middle, and distal regions, and the maximal neointimal thickness (B-mode) and hemodynamic parameters were recorded. Pre-interventional plaques were assigned to three types: soft, fibrous, and largely calcified.

RESULTS

The diameters of the self-expanding stents steadily increased over 2 years (positive arterial remodeling), from (mean +/- SD) 5.80 +/- 0.89 mm to 6.77 +/- 0.98 mm in the proximal stent area, from 3.51 +/- 0.76 mm to 4.92 +/- 0.89 mm in the middle stent area, and from 3.7 +/- 0.5 mm to 4.68 +/- 0.61 mm in the distal stent area (P<.001). Stent expansion was most marked in the middle stent area, depending on the type of pre-interventional plaque. The extent in stent expansion was more in soft than in fibrous and calcified plaques (P<.001). Neointimal thickness increased up to 12 months, and stabilized thereafter. The mean (+/- SD) neointimal thickness at 3, 6, 12, and 24 months was 0.61 +/- 0.28 mm, 0.97 +/- 0.39 mm, 1.06 +/- 0.36 mm, and 1.12 +/- 0.38 mm, respectively. These complex interactions resulted in the dominance of negative remodeling secondary to neointimal proliferation, with an increased flow ratio during the first year, from 1.16 +/- 0.37 at day 1 to 1.23 +/- 0.46 at 3 months, 1.67 +/- 1.37 at 6 months, and 1.57 +/- 0.70 at 12 months (P<.001), followed by a tendency to decrease as a result of stent expansion thereafter (flow ratio at 24 months, 1.49 +/- 0.70). Two of 121 stents (1.6%) had recurrent stenosis that required a secondary procedure.

CONCLUSIONS

Neointimal proliferation or negative arterial remodeling prevails up to 12 months, and may give rise to rare stent recurrent stenosis. Stent expansion reduces this effect in the first year, and dominates in the second year. This might contribute to the good mid-term outcome of carotid stenting. Poor stent expansion in heavily calcified plaques calls for primary surgical management.