Restenosis in coronary bare metal stents. Importance of time to follow-up: a comparison of coronary angiograms 6 months and 4 years after implantation

OBJECTIVES: Angiographic late lumen loss measured 6 to 9 month after bare metal stent implantation in the coronary arteries is a validated restenosis parameter.

DESIGN: We performed a second angiographic follow-up after 4 years in event free survivors from the DANSTENT trial cohort.

RESULTS: Quantitative comparison of paired coronary angiograms at 6 months and 4 years showed a reduction of late loss from 0.68+/-0.52 mm to 0.42 (+/-0.52) (mean difference 0.26 (0.17 to 0.36), p<0.0001). Minimal instent lumen diameter had increased from 2.39+/-0.62 mm to 2.64+/-0.56 mm (mean difference: -0.24 mm, 95% confidence interval: -0.34 mm to -0.14 mm, p<0.0001). Instent diameter stenosis decreased from 24.8+/-14.2% to 18.6+/-9.3% (mean difference 6.16%, 95% confidence interval: 2.82 to 9.48%, p=0.0006). This observed spontaneous decrease of instent restenosis corresponds to a 19% increase of minimal cross-sectional vessel area and a 39% reduction of the binary restenosis rate over time.

CONCLUSIONS: Instent late lumen loss in bare metal stents decreases spontaneously over time. Maturation of early hyperplastic tissue reaction after stent implantation with subsequent thinning of fibrotic tissue might explain this phenomenon.