Follow-Up Angioscopy of Drug-Eluting Stents
Abstract & Commentary
By Michael H. Crawford, MD, Professor of Medicine, and Chief of Clinical Cardiology, at the University of California, San Francisco. Dr. Crawford is on the speaker's bureau for Pfizer.
Synopsis: The DES had incomplete neointimal coverage 3-6 months after implantation, and this was associated with subclinical thrombus formation.
Source: Kotani J, et al. Incomplete Neointimal Coverage of Sirolimus-Eluting Stents: Angioscopic Findings. J Am Coll Cardiol. 2006;47:2108-2111.
Although sirolimus-eluting stents (SES) have greatly reduced restenosis, late thrombosis is an issue. One hypothesis is that inadequate neointimal coverage results in late thrombosis, especially if intense antiplatelet therapy is stopped or decreased. Thus, Kotani and colleagues from Japan performed coronary angiography and angioscopy in 37 stented lesions in 25 patients; 15 with SES and 22 with bare metal stents (BMS), 3-6 months post procedure. Coronary angioscopy assessed the degree of neointimal coverage, graded 0-3, where 0 and 1 are incomplete and 2 and 3 are complete stent coverage. The presence of thrombosis was also noted. All patients received aspirin 100 mg and ticlopidine 200 mg per day after the procedure (clopidogrel not approved then in Japan).
Results: The clinical and lesion characteristics of the SES and BMS patients were not significantly different. At follow-up, the SES group had a larger minimum luminal diameter compared to the BMS group (2.3 vs 1.8 mm, P < .03). Angioscopy identified thrombi in 8 stents. All were nonocclusive and undetected by angiography. Red thrombi were detected in 5 of 15 SES (33%) vs 1 red thrombi and 1 white thrombus in 22 BMS (14%, P = NS). Intimal coverage was markedly different in that 3 of 15 SES (20%) had grade 0 coverage and only 2 SES (13%) had complete coverage (grades 2/3). By contrast, all 22 BMS showed complete coverage (grades 0/1). Kotani et al concluded that many SES have incomplete intimal coverage at 3-6 months post procedure, and that subclinical thrombus formation is associated with incomplete coverage.
Commentary
One of the advantages of SES is that guideline recommended intensive antiplatelet therapy is for 3 months minimum vs 6 months for paclitaxel-eluting stents. However, this study suggests that neointimal stent coverage is incomplete in most patients at 3 to 6 months with SES. Thus, it would seem prudent to recommend dual antiplatelet therapy for longer than the minimal recommendations. Just how long is unclear, but many are recommending at least a year.
There are several limitations to his study. It is small, and there were apparently no clinical events. On the other hand, angioscopic studies are difficult to do, and there is very little such data. Intravascular ultrasound (IVUS) cannot provide this quality of data regarding intimal coverage, but what little IVUS data are available support the conclusions of this study. The BMS and SES used in this study were not structurally identical, so the effect of stent structure cannot be ascertained. This is a single cross-sectional analysis; there is no serial data to examine the time course of neointimalization. There could be rapid intimal catch-up once the sirolimus has largely eluted. Since all the angioscopies were done at ≤ 6 months, such a catch-up could occur shortly after 6 months. Also, angioscopy only assesses neointimal anatomy not function. Thus, it is possible that minimal coverage (grade 1) may be functionally adequate. Finally, we do not know if clopidogrel use would have produced different results than ticlopidine.
The DES had incomplete neointimal coverage 3-6 months after implantation, and this was associated with subclinical thrombus formation.You have reached your article limit for the month. Subscribe now to access this article plus other member-only content.
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