Intravascular ultrasound assessment of the balloon-expandable Palmaz-Schatz coronary stent.

BACKGROUND

Coronary stenting is an effective method for the treatment of acute coronary dissection and restenosis. In the comprehensive assessment of restenosis and of the complex interaction between coronary stent and vessel wall, coronary arteriography has significant limitations. Intravascular ultrasound as a high-resolution tomographic imaging method is a promising tool for resolving these limitations.

METHODS

A 3.5, 5.0 or 5.5F, 20 MHz multi-element ultrasound catheter was used in 27 patients who had received a Palmaz-Schatz coronary stent for the treatment of symptomatic coronary dissection. Intravascular ultrasound study was performed during routine follow-up arteriography at 3-10 months in all 27 patients and had also been performed in four patients during stent deployment. Four patients with restenosis within the stent were re-investigated 3 months later after repeat angioplasty.

RESULTS

Complete analysis of the stented coronary segment could be performed in 34 out of 35 studies (97%); no adverse effects occurred. The three layer appearance of the vessel wall was not discernible in most patients because of a complex and often eccentric lesion surrounding the stent resulting in an asymmetrical arrangement of stent filaments. The beginning and the end of the stent, the central strut, and the overlap of a double stent could be well assessed. Luminal diameters ranged from 1.95 to 4.15 mm and cross-sectional areas from 3.83 to 10.85 mm2. Correlations with quantitative arteriography revealed r-values of 0.58 for diameter and 0.59 for area. A stent-covering layer, indicative of neointima, was clearly visible in all patients during follow-up arteriography with a diameter of 0.10-0.95 mm (mean 0.25 +/- 0.15 mm), which resulted in a reduction of 2-63% in the cross-sectional area of the vessel. This layer did not exceed a thickness of 0.4 mm in asymptomatic patients.

CONCLUSIONS

This study demonstrates the safe and feasible application of intravascular ultrasound in patients with stented coronary lesions. Differences between the angiographic and ultrasonic measurements are presumably the result of the limitations of radiography in complex and eccentric lesions. Intracoronary ultrasound provides a unique comprehensive assessment of stent expansion, neointimal proliferation, and restenosis mechanisms. Thus, intravascular ultrasound may also have implications regarding the indication for, and optimal deployment of, intracoronary stents.