The evaluation of intracoronary stents by intravascular echography

BACKGROUND: Intravascular ultrasound (IVUS) provides high resolution of vessel wall pathoanatomy, and because of the highly reflective nature of stent surfaces, can evaluate alterations in stent geometry. METHODS: This study was performed to assess, by IVUS stent, expansion patterns in patients undergoing implantation of metallic coronary stents, and the mechanisms of restenosis in those patients. Twenty-five patients were studied: 9 pts acutely and 16 pts at routine follow-up 5-8 months after Palmaz-Schatz stent placement. The images recorded by IVUS (25 Mhz 3.9F catheter Intertherapy Inc. California) were quantitatively analyzed for: luminal diameter (LD), luminal cross-sectional area (LA), cross-sectional diameter (SD) and area (SA), comprised by the stent struts. We used quantitative coronary angiography (QCA) (Image Comm System) to measure lumen diameter (LD) and luminal cross-sectional area (LA) in patients in whom IVUS was not performed at the moment of stent placement. These values were considered reference values of LD and LA of the stent at follow-up. RESULTS: During follow-up, patients showed a reduction of vessel lumen LD (2.09 +/- 0.17 mm) measured by IVUS, versus baseline LD (2.87 +/- 0.39 mm) measured by QCA. SD (2.76 +/- 0.31 mm) and SA (6.30 +/- 1.24 mm2) were unchanged in comparison with LD (2.87 +/- 0.39 mm) and LA (6.47 +/- 1.77 mm2) measured by QCA at the time of stent implantation. CONCLUSIONS: These data suggest that the mechanism of restenosis is due to intimal proliferation rather than stent collapse.