Mechanisms and patterns of intravascular ultrasound in-stent restenosis among bare metal stents and first- and second-generation drug-eluting stents

Selected in The American Journal of Cardiology by D. Milasinovic

References

Authors

Goto K, Zhao Z, Matsumura M, Dohi T, Kobayashi N, Kirtane AJ, Rabbani LE, Collins MB, Parikh MA, Kodali SK, Leon MB, Moses JW, Mintz GS, Maehara A

Reference

Am J Cardiol. 2015 Nov 1;116(9):1351-7

Published

November 2015

Link

Read the abstract

My Comment

What is known

Previous studies showed that stent underexpansion, fracture and neointimal hyperplasia (NIH) are among primary contributing factors to in-stent restenosis (ISR). The present study investigated the comparative impact of these factors in patients treated with second-generation drug-eluting stents (DES), compared to bare metal stents (BMS) and first-generation DES.

Methodology

  • Retrospective analysis of 298 patients and 298 ISR lesions who underwent follow-up with intravascular ultrasound (IVUS) from October 2009 to April 2014;
  • ISR was defined as IVUS-measured in-stent minimum lumen area (MLA) < 4mm2;
  • The analysis included 52 BMS, 138 first-generation DES (73 Cypher, 52 Taxus, 13 Endeavor) and 108 second-generation DES (39 Promus, 66 Xience, 3 Resolute).  

Major findings

  • External elastic membrane (EEM) and lumen areas at proximal and distal reference segments and lesion site were similar among the three groups.
  • At the site of MLA:
    - Stent cross-sectional area (CSA) was larger in BMS compared with 1st- and 2nd- generation DES (7.2 vs. 6.1 vs. 5.7 mm2, p<0.001);
    - Stent CSA < 5mm2, as criterion for underexpansion, tended to be the most frequent in 2nd-generation DES (22% in BMS vs. 31% in 1st- vs. 40% in 2nd-generation DES, p=0.07);
    - The rate of NIH exceeding 50% of the stent area was similar among the groups (77% in BMS vs. 75% in 1st-generation DES vs. 66% in 2nd-generation DES, p=0.25).
  • The dominant mechanism of ISR was deemed to be:
    - Intimal hyperplasia, in case of stent CSA >5mm2 and NIH >50% at MLA site, which was present in 69% vs. 59% of patients with BMS and DES, respectively;
    - Underexpansion, in case of stent CSA < 5mm2 and NIH <50% at MLA site, which was present more frequently in patients treated with DES (18% vs 14%).
  • Stent fractures were observed only in patients with DES (7 fractures in 1st- and 8 fractures in 2nd-generation DES).

My comment

Given the inherent limitations of a retrospective analysis, the higher rate of underexpansion-dominated ISR and stent fractures in patients with DES compared to BMS may highlight the need for further advancements in the technique of stent implantation to match the rapid progress in DES technology.

Further prospective, invasive imaging-based evaluations of the complex stent healing process in patients treated with newer-generation DES are needed.

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